Expression of honey bee (Apis mellifera) sterol homeostasis genes in food jelly producing glands of workers

Adult workers of Western honey bees (Apis mellifera L.) acquire sterols from their pollen diet. These food sterols are transported by the hemolymph to peripheral tissues such as the mandibular and the hypopharyngeal glands in the worker bees' heads that secrete food jelly which is fed to developing larvae. As sterols are obligatory components of biological membranes and essential precursors for molting hormone synthesis in insects, they are indispensable to normal larval development. Thus, the study of sterol delivery to larvae is important for a full understanding of honey bee larval nutrition and development. Whereas hypopharyngeal glands only require sterols for their membrane integrity, mandibular glands add sterols, primarily 24-methylenecholesterol, to its secretion. For this, sterols must be transported through the glandular epithelial cells. We have analyzed for the first time in A. mellifera the expression of genes which are involved in intracellular movement of sterols. Mandibular and hypopharyngeal glands were dissected from newly emerged bees, 6-day-old nurse bees that feed larvae and 26-day-old forager bees. The expression of seven genes involved in intracellular sterol metabolism was measured with quantitative real-time PCR. Relative transcript abundance of sterol metabolism genes was significantly influenced by the age of workers and specific genes but not by gland type. Newly emerged bees had significantly more transcripts for six out of seven genes than older bees indicating that the bulk of the proteins needed for sterol metabolism are produced directly after emergence.

Mandibular glands secrete 24-methylenecholesterol into honey bee (Apis mellifera) food jelly

Honey bee (Apis mellifera) workers feed their larvae with food jelly that is secreted by specialized glands in their heads - the hypopharyngeal and the mandibular glands. Food jelly contains all the nutrients the larvae need to develop into adult honey bees, including essential dietary sterols. The main sterol in food jelly, 24-methylenecholesterol (24MC), is pollen-derived and delivered in food jelly to the larvae in a complex with two proteins, major royal jelly protein 1 (MRJP1) and apisim. Whereas the proteins are synthesized in the hypopharyngeal glands, the sterol-secreting gland has not been identified. We here identified the mandibular glands as sterol-secreting gland for food jelly production by direct detection of the four main honey bee sterols (24MC, campesterol, β-sitosterol and isofucosterol). Furthermore, 24MC seems to be specifically enriched in the mandibular glands, thereby ensuring that food jelly contains the amounts of 24MC necessary for complex formation with MRJP1 and apisimin.

Differences in the suitability of published honey bee (Apis mellifera) reference genes between the African subspecies Apis mellifera scutellata and European derived Apis mellifera

Quantitative real-time polymerase chain reaction (qPCR) is a method widely used to determine changes and differences in gene expression. As target gene expression is most often quantified relative to the expression of reference genes, the validation of suitable reference genes is of critical importance. In practice, however, such validation might not be thoroughly conducted if the same species and the same tissue or body parts are used for qPCR experiments. Here we show, that qPCR reference genes published for workers of European honey bee (Apis mellifera) subspecies fail to be stably expressed in workers of the African subspecies Apis mellifera scutellata. This is the case even when the sampled workers are in the same life stage, the same organ was dissected and the same reagents were used. Thus, reference genes need to be thoroughly re-tested before they can be used as suitable references even when the only thing that changes is the subspecies used.

Spatial distribution of Glossina morsitans (Diptera: Glossinidae) in Zambia: A vehicle-mounted sticky trap survey and Maxent species distribution model

BACKGROUND

Tsetse-transmitted African trypanosomiasis is a debilitating and fatal disease of humans and livestock if left untreated. While knowledge of the spatial distribution patterns of tsetse is essential for the development of risk-based vector control strategies, existing distribution maps in Zambia are more than 40 years old and were based on coarse spatial resolution data. The recently developed vehicle-mounted sticky trap (VST) provides an alternative sampling device to aid in updating existing distribution maps but has not been applied outside an experimental setting and is limited to motorable tracks. Therefore, the objective of the present study was to demonstrate the effectiveness of utilizing the VST for area-wide surveys of Glossina morsitans and to use the occurrence records to predict its spatial distribution in Zambia under current environmental conditions using Maxent.

METHODOLOGY/PRINCIPAL FINDINGS

Two-sided all-blue VST baited with butanone and 1-octen-3-ol was used to survey 692 and 1020 km of transect routes in G. m. centralis Machado and G. m. morsitans Westwood previously published distribution in Zambia. Maxent species distribution technique was used to predict the potential distribution of the two subspecies using current climatic and environmental data which was then compared to the historical distribution. A total of 15,602 tsetse were captured with G. m. morsitans (58%) being the most abundant. G. m. centralis and G. pallidipes Austin represented 39 and 2% of the catch respectively, and G. brevipalpis Newstead was also detected. The predicted potential distribution for G. m. centralis was 80,863 km2 while that of G. m. morsitans was 70,490 km2 representing a 47 and 29% reduction compared to their historical distributions, respectively.

CONCLUSION/SIGNIFICANCE

The VST is effective for sampling G. morsitans outside experimental settings and is recommended for use as an additional tsetse survey tool. The spatial distribution of G. morsitans in Zambia has reduced by 101,051 km2 due to temperature and land cover changes.

Seasonal and elevational changes of plant-pollinator interaction networks in East African mountains

Across an elevation gradient, several biotic and abiotic factors influence community assemblages of interacting species leading to a shift in species distribution, functioning, and ultimately topologies of species interaction networks. However, empirical studies of climate-driven seasonal and elevational changes in plant-pollinator networks are rare, particularly in tropical ecosystems. Eastern Afromontane Biodiversity Hotspots in Kenya, East Africa. We recorded plant-bee interactions at 50 study sites between 515 and 2600 m asl for a full year, following all four major seasons in this region. We analysed elevational and seasonal network patterns using generalised additive models (GAMs) and quantified the influence of climate, floral resource availability, and bee diversity on network structures using a multimodel inference framework. We recorded 16,741 interactions among 186 bee and 314 plant species of which a majority involved interactions with honeybees. We found that nestedness and bee species specialisation of plant-bee interaction networks increased with elevation and that the relationships were consistent in the cold-dry and warm-wet seasons respectively. Link rewiring increased in the warm-wet season with elevation but remained indifferent in the cold-dry seasons. Conversely, network modularity and plant species were more specialised at lower elevations during both the cold-dry and warm-wet seasons, with higher values observed during the warm-wet seasons. We found flower and bee species diversity and abundance rather than direct effects of climate variables to best predict modularity, specialisation, and link rewiring in plant-bee-interaction networks. This study highlights changes in network architectures with elevation suggesting a potential sensitivity of plant-bee interactions with climate warming and changes in rainfall patterns along the elevation gradients of the Eastern Afromontane Biodiversity Hotspot.

Honey bees save energy in honey processing by dehydrating nectar before returning to the nest

Honey bees process nectar into honey by active evaporation on the tongue and passive evaporation involving nest ventilation and fanning behaviour, as well as enzymatic action. The elimination of excess water from nectar carries considerable energetic costs. The concentration of the nectar load is assumed to remain constant during transport. However, some of this water elimination may occur before foragers return to the nest and pass their nectar loads to receiver bees. In honey bees captured while foraging in Macadamia orchards, we show that the nectar in their crops has approximately twice the sugar concentration of the fresh nectar in flowers. This was true for four Macadamia cultivars, with up to 75% of the initial water content being removed. There is a further concentration increase in the crops of returning bees captured at the hive entrance. The only possible route of water elimination from the crop is via evaporation from the mouthparts. We calculate the savings in honey processing costs to be on average 35 times more than the reduction in flight costs due to reduced body mass. Pre-concentration of nectar in foraging honey bees may be widespread, and of crucial importance for honey storage.

Predicting the potential distribution of a previously undetected cryptic invasive synanthropic Asian house rat (Rattus tanezumi) in South Africa

Three species of Rattus, Norway rat (R. norvergicus), black rat (R. rattus) and Asian house rat (R. tanezumi) are currently known to occur in South Africa. The latter two species are cryptic and form part of the Rattus rattus species complex. Historically, R. norvegicus has been reported to occur along the coast and in urban centres, R. rattus is widespread in most urban areas, except in the drier areas, while R. tanezumi was only recorded to occur in the country (and Africa) ca. 15 years ago, and its distribution remains unknown. The aim of this study was to predict the potential distribution of R. tanezumi in South Africa and assess how it overlaps with that of R. norvegicus and R. rattus using species distribution modelling. Rattus tanezumi was predicted to mainly occur in most inland urban areas and along the coast. The distribution of R. rattus was as expected, in contrast, the predicted range of R. norvegicus was not restricted to the coast but also included inland urban areas. All three species showed broad potential distributional ranges that overlapped extensively indicating that their establishment and spread may be influenced by similar factors such as proximity to urban areas and a wet and moderate climate. These results allow insights into assessing their risk of establishment and for formulating appropriate intervention strategies for their management and control.

Chemical Cues From Honeydew and Cuticular Extracts of Trialeurodes Vaporariorum Serve as Kairomones for The Parasitoid Encarsia Formosa

Kairomones are semiochemicals that are emitted by an organism and which mediate interspecific interaction that is of benefit to an organism of another species that receives these chemical substances. Parasitoids find and recognize their hosts through eavesdropping on the kairomones emitted from the by-products or the body of the host. Hemipteran insect pests feed on plant sap and excrete the digested plant materials as honeydew. Honeydew serves as a nutritional food source for parasitoids and a medium for micro-organisms whose activity induces the release of volatiles exploited by parasitoids for host location. The parasitoid Encarsia formosa preferentially parasitizes its host, the greenhouse whitefly, Trialeurodes vaporariorum, on tomato Solanum lycopersicum, but little is known about the chemicals that mediate these interactions. We investigated the olfactory responses of the parasitoid E. formosa to odours from honeydew and nymphs of T. vaporariorum in a Y-tube olfactometer. Arrestment behaviour of the parasitoid to honeydew and nymph extracts, as well as to synthetic hydrocarbons, was also observed in Petri-dish bioassays. We found that T. vaporariorum honeydew volatiles attracted the parasitoid E. formosa but odours from the whitefly nymphs did not. We also found that the parasitoid spent more time searching on areas treated with extracts of honeydew and nymphs than on untreated areas. Gas-chromatography-mass spectrometric analysis revealed that the honeydew volatiles contained compounds such as (Z)-3-hexenol, δ-3-carene, 3-octanone, α-phellandrene, methyl salicylate, β-ocimene, β-myrcene, and (E)-β-caryophyllene which are known to be attractive to E. formosa. The cuticular extracts of the nymphs predominantly contained alkanes, alkenes, and esters. Among the alkanes, synthetic nonacosane arrested the parasitoid. Our findings are discussed in relation to how the parasitoid E. formosa uses these chemicals to locate its host, T. vaporariorum.

The Diversity Decline in Wild and Managed Honey Bee Populations Urges for an Integrated Conservation Approach

Many parts of the globe experience severe losses and fragmentation of habitats, affecting the self-sustainability of pollinator populations. A number of bee species coexist as wild and managed populations. Using honey bees as an example, we argue that several management practices in beekeeping threaten genetic diversity in both wild and managed populations, and drive population decline. Large-scale movement of hive stocks, introductions into new areas, breeding programs and trading of queens contribute to reducing genetic diversity, as recent research demonstrated for wild and managed honey bees within a few decades. Examples of the effects of domestication in other organisms show losses of both genetic diversity and fitness functions. Cases of natural selection and feralization resulted in maintenance of a higher genetic diversity, including in a Varroa destructor surviving population of honey bees. To protect the genetic diversity of honey bee populations, exchange between regions should be avoided. The proposed solution to selectively breed all local subspecies for a use in beekeeping would reduce the genetic diversity of each, and not address the value of the genetic diversity present in hybridized populations. The protection of Apis mellifera’s, Apis cerana’s and Apis koschevnikovi’s genetic diversities could be based on natural selection. In beekeeping, it implies to not selectively breed but to leave the choice of the next generation of queens to the colonies, as in nature. Wild populations surrounded by beekeeping activity could be preserved by allowing Darwinian beekeeping in a buffer zone between the wild and regular beekeeping area.

Functional response of the hypopharyngeal glands to a social parasitism challenge in Southern African honey bee subspecies

Hypopharyngeal gland (HPG) development in honey bee workers is primarily age-dependent and changes according to the tasks performed in the colony. HPG activity also depends on colony requirements and is flexible in relation to the need for feeding brood. Very little is known about HPG development in the honey bee subspecies found in Southern Africa. We examined HPG development in Apis mellifera scutellata and A. m. capensis, including A. m. scutellata colonies infested with an invasive parasitic clonal lineage of A. m. capensis known to manipulate food provisioning to the parasitic larvae by their A.m. scutellata hosts, under natural in-hive conditions in bees aged 0 to 14 days using light microscopy. We found marked differences in acini size (berry-like clusters of secretory cells) and the age at which maximum HPG development occurred between the subspecies and in the presence of the parasite. In A. m. scutellata workers, acini reached maximum size at 6 days. The acini of A. m. capensis workers were larger (up to double) than those of A. m. scutellata and reached maximum size at 8 days, while the HPG acini in A. m. scutellata workers infested with A. m. capensis clones reached development sizes similar to those of A. m. capensis at day 10 and were 1.5 times larger than those of uninfested A. m. scutellata. This provides foundational insights into a functional response affecting the development of the HPG most likely associated with brood pheromone composition and how this is altered in the presence of a social parasite.

Efficiencies of stationary sampling tools for the tsetse fly Glossina fuscipes fuscipes in western Kenya

Monitoring the effectiveness of tsetse fly control interventions that aim to reduce transmission of African trypanosomiasis requires highly efficient sampling tools that can catch flies at low densities. The sticky small target (StS-target) has previously been shown to be more effective in sampling Glossina fuscipes fuscipes compared to the biconical trap. However, its efficiency in terms of the proportion of flies it catches out of those that visit it has not been reported. Furthermore, there are no reports on whether tsetse samples caught using the StS-target can be used for subsequent processes such as molecular tests. In this study, we evaluated the efficiency of the biconical trap and targets for sampling G. f. fuscipes. All targets were tiny (0.25 × 0.50 m) but varied in their capture system. We used targets with sticky surface (StS-targets) and those with an electrified surface (ES-targets). We also assessed the suitability of flies caught on the StS-target for molecular tests by amplifying DNA of bacterial communities. Randomized block design experiments were undertaken in Mbita area and Manga Island on Lake Victoria of western Kenya. Fly catches of each sampling tool were compared to those of the sampling tool flanked by electric (E) nets and analyzed using a negative binomial regression. The total catch for each sampling tool alone was divided by the total catch of the sampling tool flanked by two E-nets to obtain its efficiency expressed as a percentage. A proportion of flies caught on the StS-target was preserved for molecular tests. Overall, the efficiencies of the biconical trap, ES-target and StS-target were 7.7%, 13.3% and 27.0%, respectively. A higher proportion of females (69 to 79%) than males approached all the sampling tools, but the trap efficiency was greater for male G. f. fuscipes than females. Furthermore, sequencing the 16S rRNA gene from fly samples caught on the StS-target revealed the presence of Spiroplasma. Our results indicate that the SS-target is the most efficient trap to monitor G. f. fuscipes population during interventions, with the biconical trap being the least efficient, and samples collected from StS-targets are suitable for molecular studies.

A novel vehicle-mounted sticky trap; an effective sampling tool for savannah tsetse flies Glossina morsitans morsitans Westwood and Glossina morsitans centralis Machado

BACKGROUND

Black screen fly round (BFR) is a mobile sampling method for Glossina morsitans. This technique relies on the ability of operator(s) to capture flies landing on the screen with hand nets. In this study, we aimed to evaluate a vehicle-mounted sticky panel trap (VST) that is independent of the operator's ability to capture flies against BFR, for effective and rapid sampling of G. m. morsitans Westwood and G. m. centralis Machado. We also determined the influence of the VST colour (all-blue, all-black or 1:1 blue-black), orientation and presence of odour attractants on tsetse catch.

METHODOLOGY/PRINCIPAL FINDINGS

Using randomised block design experiments conducted in Zambia, we compared and modelled the number of tsetse flies caught in the treatment arms using negative binomial regression. There were no significant differences in the catch indices of the three colour designs and for in-line or transversely oriented panels for both subspecies (P > 0.05). When baited with butanone and 1-octen-3-ol, VST caught 1.38 (1.11-1.72; P < 0.01) times more G. m. centralis flies than the un-baited trap. Attractants did not significantly increase the VST catch index for G. m. morsitans (P > 0.05). Overall, the VST caught 2.42 (1.91-3.10; P < 0.001) and 2.60 (1.50-3.21; P < 0.001) times more G. m. centralis and G. m. morsitans respectively, than the BFR. The VST and BFR took 10 and 35 min respectively to cover a 1 km transect.

CONCLUSION/SIGNIFICANCE

The VST is several times more effective for sampling G. m. morsitans and G. m. centralis than the BFR and we recommend its use as an alternative sampling tool.

Biological traits of wild-caught populations of Aedes aegypti in dengue endemic and non-endemic regions of Kenya

Variation in vector traits can modulate local scale differences in pathogen transmission. Here, we compared seasonal variation in the wing length (proxy for body size) and energy reserves of adult wild-caught Aedes aegypti populations from a dengue endemic (Kilifi) and non-endemic (Isiolo) area of Kenya. Vector sampling in the dengue endemic site was conducted during the dry and wet seasons. In the non-endemic area, it was limited to the dry season which characterizes this ecology where sporadic or no rainfall is commonplace during the year. We found variation by site in the body size of both sexes, with an overall smaller size of Ae. aegypti populations collected from Isiolo than those from Kilifi. Our results show that although total carbohydrates and lipids levels were highest in both sexes during the dry season, they were two-fold higher in males than females. However, we found weak correlations between body size and energy reserves for both sexes, with body size being more sensitive in identifying differences at a population level. These results provide insights into the determinants of the vectoring potential of Ae. aegypti populations in dengue endemic and non-endemic ecologies in Kenya.

Exploring the Kairomone-Based Foraging Behaviour of Natural Enemies to Enhance Biological Control: A Review

Kairomones are chemical signals that mediate interspecific interactions beneficial to organisms that detect the cues. These attractants can be individual compounds or mixtures of herbivore-induced plant volatiles (HIPVs) or herbivore chemicals such as pheromones, i.e., chemicals mediating intraspecific communication between herbivores. Natural enemies eavesdrop on kairomones during their foraging behaviour, i.e., location of oviposition sites and feeding resources in nature. Kairomone mixtures are likely to elicit stronger olfactory responses in natural enemies than single kairomones. Kairomone-based lures are used to enhance biological control strategies via the attraction and retention of natural enemies to reduce insect pest populations and crop damage in an environmentally friendly way. In this review, we focus on ways to improve the efficiency of kairomone use in crop fields. First, we highlight kairomone sources in tri-trophic systems and discuss how these attractants are used by natural enemies searching for hosts or prey. Then we summarise examples of field application of kairomones (pheromones vs. HIPVs) in recruiting natural enemies. We highlight the need for future field studies to focus on the application of kairomone blends rather than single kairomones which currently dominate the literature on field attractants for natural enemies. We further discuss ways for improving kairomone use through attract and reward technique, olfactory associative learning, and optimisation of kairomone lure formulations. Finally, we discuss why the effectiveness of kairomone use for enhancing biological control strategies should move from demonstration of increase in the number of attracted natural enemies, to reducing pest populations and crop damage below economic threshold levels and increasing crop yield.

Prisoners receive food fit for a queen: honeybees feed small hive beetles protein-rich glandular secretions through trophallaxis

The honeybee nest parasite Aethina tumida (small hive beetle) uses behavioural mimicry to induce trophallactic feeding from its honeybee hosts. Small hive beetles are able to induce honeybee workers to share the carbohydrate-rich contents of their crops, but it is not clear whether the beetles are able to induce to workers to feed them the protein-rich hypopharyngeal glandular secretions fed to the queen, larvae and other nest mates. Protein is a limiting macronutrient in an insect's diet, essential for survival, growth and fecundity. Honeybees obtain protein from pollen, which is consumed and digested by nurse bees. They then distribute the protein to the rest of the colony in the form of hypopharyngeal gland secretions. Using ¹⁴C-phenylalanine as a qualitative marker for protein transfer, we show that small hive beetles successfully induce worker bees to feed them the protein-rich secretions of their hypopharyngeal glands during trophallaxis, and that females are more successful than males in inducing the transfer of these protein-rich secretions. Furthermore, behavioural observations demonstrated that female beetles do not preferentially interact with a specific age cohort of bees when soliciting food, but males tend to be more discriminant and avoid the more aggressive and active older bees.

Plant nutrient quality impacts survival and reproductive fitness of the dengue vector Aedes aegypti

BACKGROUND

In a recent study using DNA barcoding, we identified the plants fed upon by four Afro-tropical mosquito species that vector dengue, malaria, and Rift Valley fever. Herein, we have expanded on this study by investigating the role of three of the plants, Pithecellobium dulce (Fabaceae), Leonotis nepetifolia (Lamiaceae), and Opuntia ficus-indica (Cactaceae), on the survival, fecundity, and egg viability of the dengue vector Aedes aegypti.

METHODS

We tested these effects using females that received (i) an initial three rations of blood meals and (ii) no blood meal at all. Two controls were included: age-matched females fed on glucose solution with or without an initial blood meal and those fed exclusively on blood meals. Data were collected daily over a 30-day period. The amino acid contents of Ae. aegypti guts and their respective diets were detected by coupled liquid chromatography-mass spectrometry.

RESULTS

Females fed on P. dulce and an exclusively blood meal diet had a shorter survival than those fed on glucose. On the other hand, females fed on L. nepetifolia survived longer than those fed exclusively on blood meals, whereas those fed on O. ficus-indica had the shortest survival time. With an initial blood meal, females fed on L. nepetifolia laid 1.6-fold more eggs while those fed on the other diets laid fewer eggs compared to those fed exclusively on blood meals. Hatching rates of the eggs laid varied with the diet. Mass spectroscopic analysis of gut contents of mosquitoes exposed to the different diets showed qualitative and quantitative differences in their amino acid levels.

CONCLUSION

Our findings highlight the central role of plant nutrients in the reproductive fitness of dengue vectors, which may impact their disease transmission potential.

Odor-Mediated Group Organization and Coordination in the Termite-Raiding Ant Megaponera analis (Mayr)

Visual and olfactory communications are vital for coordinated group hunting in most animals. To hunt for prey, the group-raiding termite specialist ant Megaponera analis, which lacks good vision, must first confirm the presence or absence of conspecific raiders. Here, we show that M. analis uses olfactory cues for intraspecific communication and showed greater preference for conspecific odors over clean air (blank) or odors from its termite prey. Chemical analysis of ant volatiles identified predominantly short-chained hydrocarbons. Electrophysiological analysis revealed differential sensory detection of the odor compounds, which were confirmed in behavioral olfactometric choice assays with odor bouquets collected from major and minor castes and the 2 most dominant volatiles and n-undecane n-tridecane. A comparative analysis of the cuticular hydrocarbon profile with those of the short-chained odor bouquet of different populations shows a high divergence in the long-chained profile and a much-conserved short-chained odor bouquet. This suggests that there is less selection pressure for divergence and individual recognition in the short- than the long-chained odor profiles. We conclude that olfactory communication serves as an alternative to visual or sound communication, especially during group raids in M. analis when ants are not in direct contact with one another.

Temperature-dependent development and survival of immature stages of the coffee berry borer Hypothenemus hampei (Coleoptera: Curculionidae)

Although the coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae) is the most destructive insect pest of coffee worldwide, there is much to learn about its thermal biology. This study aimed to develop temperature-based models for H. hampei development and to provide the thermal requirements of immature stages in the laboratory. Using a new observation method, larval development and survival were monitored daily on fresh Arabica coffee seeds, under seven constant temperatures in the range 15-35°C, with 80 ± 5% RH and 12:12 L:D photoperiod. Linear and non-linear functions were fitted to the development data plotted against temperature, using Insect Life Cycle Modelling software (ILCYM). Temperature significantly affected the development time of all immature stages. Egg incubation period ranged 4.6-16.8 days, under temperature between 30 and 15°C. No development occurred at 35°C and the larval stage did not develop to pupa at 15°C. The minimum temperature threshold (Tmin) estimated from linear regression was 10.5, 13.0, 15.0 and 13.0°C, for egg, larva, pupa and the total development from egg to adult, respectively. The maximum temperature threshold (Tmax) estimated from the Sharpe and DeMichele function was 32°C for egg to adult development. The thermal constant (k) was estimated at 78.1, 188.7, 36.5 and 312.5 degree days, for egg, larva, pupa and for egg to adult, respectively. Our results will help understand and predict the pest population dynamics and distribution in coffee plantations as impacted by temperature, and as such, will contribute to a more efficient management of the pest.

Hydroxylation patterns associated with pheromone synthesis and composition in two honey bee subspecies Apis mellifera scutellata and A. m. capensis laying workers

Colony losses due to social parasitism in the form of reproductive workers of the Apis mellifera capensis clones results from the production of queen-like pheromonal signals coupled with ovarian activation in these socially parasitic honey bees. While the behavioral attributes of these social parasites have been described, their genetic attributes require more detailed exploration. Here, we investigate the production of mandibular gland pheromones in queenless workers of two sub-species of African honey bees; A. m. scutellata (low reproductive potential) and A. m. capensis clones (high reproductive potential). We used standard techniques in gas chromatography to assess the amounts of various pheromone components present, and qPCR to assess the expression of cytochrome P450 genes cyp6bd1 and cyp6as8, thought to be involved in the caste-dependent hydroxylation of acylated stearic acid in queens and workers, respectively. We found that, for both subspecies, the quality and quantity of the individual pheromone components vary with age, and that from the onset, A. m. capensis parasites make use of gene pathways typically upregulated in queens in achieving reproductive dominance. Due to the high production of 9-hydroxy-decenoic acid (9-HDA) the precursor to the queen substance 9-oxo-decenoic acid (9-ODA) in newly emerged capensis clones, we argue that clones are primed for parasitism upon emergence and develop into fully fledged parasites depending on the colony's social environment.

Thermal regulatory mechanisms of termites from two different savannah ecosystems

Termites are known for their abilities to regulate the conditions within their nests through the mounds that they build or the location of the built mound which assist in keeping the internal temperature within the requirement of the colony. These mechanisms to regulate vary between species, with some species adapting passive behaviours such as nest site selection and nest structures that permit passive heating or cooling. Here we studied seven species of mound building termites from five genera in two different savannah (Sahel and Sudan) and determined some of their passive thermal control strategies. Seven species of termites; Amitermes sp., Cubitermes oculatus, Macrotermes bellicosus, M. subhyalinus, Odontotermes sp., Trinervitermes sp. A and Trinervitermes sp. B were identified from the two savannah, We found no significant difference in internal mound temperatures between the species. In both savannah types most of the termites built their nest under the shade. We discuss the adaptive implications of building mounds under the shades as seen in species of M. bellicosus, M. subhyalinus and Odontotermes sp. Or those building mounds with unique shapes as seen in C. oculatus with mushroom shaped mounds for their role in thermal regulation within the nest and how this represents a response to environmental conditions.

Honeybee Evolution: Royal Jelly Proteins Help Queen Larvae to Stay on Top

A new study shows that, in honey bees, the main role of certain proteins in royal jelly is to ensure that the larva stays in its cell, thereby allowing it to develop into a queen.

Responses of Glossina fuscipes fuscipes to visually attractive stationary devices baited with 4-methylguaiacol and certain repellent compounds in waterbuck odour

BACKGROUND

A blend of compounds (pentanoic acid, guaiacol, δ-octalactone and geranylacetone) identified in waterbuck (Kobus defassa) body odour referred to as waterbuck repellent compounds (WRC) and a synthetic repellent 4-methylguaiacol have previously been shown to repel tsetse flies from the morsitans group. However, these repellents have not been evaluated on palpalis group tsetse flies. In this study, we evaluated the effect of these repellents on catches of Glossina fuscipes fuscipes (major vector of human sleeping sickness) in biconical traps and on sticky small targets which are visually attractive to palpalis group flies. The attractive devices were baited with different doses and blends of the repellent compounds. We also assessed the effect of removal of individual constituents in the synthetic blend of WRC on catches of G. f. fuscipes.

METHODOLOGY/PRINCIPAL FINDINGS

The study was conducted in western Kenya on four islands of Lake Victoria namely Big Chamaunga, Small Chamaunga, Manga and Rusinga. The tsetse fly catches from the treatments were modeled using a negative binomial regression to determine their effect on catches. In the presence of WRC and 4-methylguaiacol (released at ≈2 mg/h and ≈1.4 mg/h respectively), catches of G. f. fuscipes were significantly reduced by 33% (P<0.001) and 22% (P<0.001) respectively in biconical traps relative to control. On sticky small targets the reduction in fly catches were approximately 30% (P<0.001) for both 4-methylguiacol and WRC. In subtractive assays, only removal of geranylacetone from WRC significantly increased catches (by 1.8 times; P <0.001) compared to the complete blend of WRC.

CONCLUSIONS/SIGNIFICANCE

We conclude that WRC and 4-methylguaiacol reduce catches of G. f. fuscipes at stationary visually attractive traps and suggest that they may serve as broad spectrum repellents for Glossina species. We recommend further studies to investigate the effects of these compounds on reduction of G. f. fuscipes attracted to human hosts as this may lead to development of new strategies of reducing the prevalence and incidence of sleeping sickness.

Zebra skin odor repels the savannah tsetse fly, Glossina pallidipes (Diptera: Glossinidae)

BACKGROUND

African trypanosomosis, primarily transmitted by tsetse flies, remains a serious public health and economic challenge in sub-Saharan Africa. Interventions employing natural repellents from non-preferred hosts of tsetse flies represent a promising management approach. Although zebras have been identified as non-preferred hosts of tsetse flies, the basis for this repellency is poorly understood. We hypothesized that zebra skin odors contribute to their avoidance by tsetse flies.

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated the effect of crude zebra skin odors on catches of wild savannah tsetse flies (Glossina pallidipes Austen, 1903) using unbaited Ngu traps compared to the traps baited with two known tsetse fly management chemicals; a repellent blend derived from waterbuck odor, WRC (comprising geranylacetone, guaiacol, pentanoic acid and δ-octalactone), and an attractant comprising cow urine and acetone, in a series of Latin square-designed experiments. Coupled gas chromatography-electroantennographic detection (GC/EAD) and GC-mass spectrometry (GC/MS) analyses of zebra skin odors identified seven electrophysiologically-active components; 6-methyl-5-hepten-2-one, acetophenone, geranylacetone, heptanal, octanal, nonanal and decanal, which were tested in blends and singly for repellency to tsetse flies when combined with Ngu traps baited with cow urine and acetone in field trials. The crude zebra skin odors and a seven-component blend of the EAD-active components, formulated in their natural ratio of occurrence in zebra skin odor, significantly reduced catches of G. pallidipesby 66.7% and 48.9% respectively, and compared favorably with the repellency of WRC (58.1%- 59.2%). Repellency of the seven-component blend was attributed to the presence of the three ketones 6-methyl-5-hepten-2-one, acetophenone and geranylacetone, which when in a blend caused a 62.7% reduction in trap catch of G. pallidipes.

CONCLUSIONS/SIGNIFICANCE

Our findings reveal fundamental insights into tsetse fly ecology and the allomonal effect of zebra skin odor, and potential integration of the three-component ketone blend into the management toolkit for tsetse and African trypanosomosis control.

A Single SNP Turns a Social Honey Bee (Apis mellifera) Worker into a Selfish Parasite

The evolution of altruism in complex insect societies is arguably one of the major transitions in evolution and inclusive fitness theory plausibly explains why this is an evolutionary stable strategy. Yet, workers of the South African Cape honey bee (Apis mellifera capensis) can reverse to selfish behavior by becoming social parasites and parthenogenetically producing female offspring (thelytoky). Using a joint mapping and population genomics approach, in combination with a time-course transcript abundance dynamics analysis, we show that a single nucleotide polymorphism at the mapped thelytoky locus (Th) is associated with the iconic thelytokous phenotype. Th forms a linkage group with the ecdysis-triggering hormone receptor (Ethr) within a nonrecombining region under strong selection in the genome. A balanced detrimental allele system plausibly explains why the trait is specific to A. m. capensis and cannot easily establish itself into genomes of other honey bee subspecies.

Neonicotinoids decrease sucrose responsiveness of honey bees at first contact

For two decades, neonicotinoid insecticides have been extensively used worldwide. Targeting neuronal receptors, they have deleterious effects on the behaviour and physiology of many insects. Bees are exposed to these insecticides in pollen and nectar while providing pollination services to agricultural crops, and neonicotinoids have been shown to impair navigation and decrease their foraging activity. We have previously reported the effect of dietary thiamethoxam on sucrose responsiveness of young worker bees. Here, we exposed caged foragers to sublethal acute doses of clothianidin, imidacloprid, and thiamethoxam, then tested them individually for sucrose responsiveness using standard methods. In addition, we tested the response to a range of sucrose solutions laced with neonicotinoids on bees previously unexposed to neonicotinoids. This paradigm mimics the situation where foragers would first encounter poisoned nectars varying in sugar concentration. Bees were exposed to the insecticides in the feeding solution for 24 h before testing, or in the test solutions, or both. The three compounds had a detrimental effect on responses to mid-to-high sucrose concentrations under all experimental conditions, and unexposed bees tested with laced sucrose displayed unexpected low responses to the higher sucrose concentrations tested. This attenuation of sucrose response is further evidence that neonicotinoids are multisensory disruptors, with potent actions against pollinators and other beneficial insects at first contact.

Prediction of insect pest distribution as influenced by elevation: Combining field observations and temperature-dependent development models for the coffee stink bug, Antestiopsis thunbergii (Gmelin)

The antestia bug, Antestiopsis thunbergii (Gmelin 1790) is a major pest of Arabica coffee in Africa. The bug prefers coffee at the highest elevations, contrary to other major pests. The objectives of this study were to describe the relationship between A. thunbergii populations and elevation, to elucidate this relationship using our knowledge of the pest thermal biology and to predict the pest distribution under climate warming. Antestiopsis thunbergii population density was assessed in 24 coffee farms located along a transect delimited across an elevation gradient in the range 1000-1700 m asl, on Mt. Kilimanjaro, Tanzania. Density was assessed for three different climatic seasons, the cool dry season in June 2014 and 2015, the short rainy season in October 2014 and the warm dry season in January 2015. The pest distribution was predicted over the same transect using three risk indices: the establishment risk index (ERI), the generation index (GI) and the activity index (AI). These indices were computed using simulated life table parameters obtained from temperature-dependent development models and temperature data from 1) field records using data loggers deployed over the transect and 2) predictions for year 2055 extracted from AFRICLIM database. The observed population density was the highest during the cool dry season and increased significantly with increasing elevation. For current temperature, the ERI increased with an increase in elevation and was therefore distributed similarly to observed populations, contrary to the other indices. This result suggests that immature stage susceptibility to extreme temperatures was a key factor of population distribution as impacted by elevation. In the future, distribution of the risk indices globally indicated a decrease of the risk at low elevation and an increase of the risk at the highest elevations. Based on these results, we concluded with recommendations to mitigate the risk of A. thunbergii infestation.

Reproductive parasitism by worker honey bees suppressed by queens through regulation of worker mandibular secretions

Social cohesion in social insect colonies can be achieved through the use of chemical signals whose production is caste-specific and regulated by social contexts. In honey bees, queen mandibular gland pheromones (QMP) maintain reproductive dominance by inhibiting ovary activation and production of queen-like mandibular gland signals in workers. We investigated whether honey bee queens can control reproductively active workers of the intraspecific social parasite Apis mellifera capensis, parasitising A. m. scutellata host colonies. Our results show that the queen’s QMP suppresses ovarian activation and inhibits the production of QMP pheromone signals by the parasitic workers, achieved through differential expression of enzymes involved in the biosynthesis of these pheromones at two points in the biosynthetic pathway. This is the first report showing that honey bee queens can regulate reproduction in intraspecific social parasites and deepens our understanding of the molecular mechanisms involved in the regulation of worker reproduction in social insects.

Digestibility and nutritional value of fresh and stored pollen for honey bees (Apis mellifera scutellata)

Pollen, the main protein source for honey bees, is mixed with regurgitated nectar or honey during collection and then stored as 'bee bread' before its consumption, mainly by young nurse workers. It has been suggested that storage of pollen improves its nutritional value and digestibility, but there is little evidence for such changes. We fed two fresh pollen types of different protein content (aloe and sunflower), and two stored pollen types (sunflower and a mixed pollen), to young caged worker bees. We measured daily consumption of pollen and sucrose solution, and survival after 14 days. At day 14 we recorded ovarian activation and extraction efficiency, by counting empty pollen grains in the rectal contents. Extraction efficiency is a measure of pollen digestibility. Contrary to our predictions, bees did not consume more fresh sunflower pollen than fresh aloe pollen to compensate for the lower protein content of sunflower pollen. In addition, they did not consume less sucrose solution when fed stored pollen diets that are already enriched in sugar. Consumption of stored sunflower pollen resulted in a low protein to carbohydrate (P:C) intake. Survival and ovarian activation were higher on diets giving higher P:C intakes. Extraction efficiency was high (up to 99%) for all pollen diets, and comparison of fresh and stored sunflower pollen showed that storage did not make it easier to digest. Changes to pollen during storage do not confer obvious benefits to honey bees.

Sticky small target: an effective sampling tool for tsetse fly Glossina fuscipes fuscipes Newstead, 1910

Background

Small targets comprising panels of blue and insecticide-treated black netting material each 0.25 × 0.25 m have been shown to attract and kill Glossina fuscipes fuscipes Newstead, 1910 (Diptera: Glossinidae) thereby reducing its population density by over 90% in field trials. However, their attractive ability has not been fully exploited for sampling purposes. Therefore, in this study we assessed the effectiveness of using sticky small targets as sampling tools for G. f. fuscipes in western Kenya. We also determined the influence of colour on the landing response of female and male flies on sticky small targets.

Methods

Using a series of randomised block experiments, the numbers of tsetse flies caught with sticky small targets were compared with those caught with biconical traps. A negative binomial regression was used to model fly catches. Odds ratios as measures of association between the landing response on the blue or black panel of the sticky small target and the sex of flies were obtained from a multiple logistic regression.

Results

The results showed that sticky small targets caught 13.5 and 3.6 times more female and male tsetse flies than biconical traps (Z = 9.551, P < 0.0001 and Z = 5.978, P < 0.0001, respectively). Females had a 1.7 times likelihood of landing on the black panel than males (Z = 2.25, P = 0.025).

Conclusion

This study suggests that sticky small targets are an effective sampling tool for G. f. fuscipes. Therefore, we recommend the use of sticky small targets as an alternative to biconical traps for observational and experimental investigations of G. f. fuscipes.

The transcriptomic changes associated with the development of social parasitism in the honeybee Apis mellifera capensis

Social insects are characterized by the division of labor. Queens usually dominate reproduction, whereas workers fulfill non-reproductive age-dependent tasks to maintain the colony. Although workers are typically sterile, they can activate their ovaries to produce their own offspring. In the extreme, worker reproduction can turn into social parasitism as in Apis mellifera capensis. These intraspecific parasites occupy a host colony, kill the resident queen, and take over the reproductive monopoly. Because they exhibit a queenlike behavior and are also treated like queens by the fellow workers, they are so-called pseudoqueens. Here, we compare the development of parasitic pseudoqueens and social workers at different time points using fat body transcriptome data. Two complementary analysis methods-a principal component analysis and a time course analysis-led to the identification of a core set of genes involved in the transition from a social worker into a highly fecund parasitic pseudoqueen. Comparing our results on pseudoqueens with gene expression data of honeybee queens revealed many similarities. In addition, there was a set of specific transcriptomic changes in the parasitic pseudoqueens that differed from both, queens and social workers, which may be typical for the development of the social parasitism in A. m. capensis.

Host plant forensics and olfactory-based detection in Afro-tropical mosquito disease vectors

The global spread of vector-borne diseases remains a worrying public health threat, raising the need for development of new combat strategies for vector control. Knowledge of vector ecology can be exploited in this regard, including plant feeding; a critical resource that mosquitoes of both sexes rely on for survival and other metabolic processes. However, the identity of plant species mosquitoes feed on in nature remains largely unknown. By testing the hypothesis about selectivity in plant feeding, we employed a DNA-based approach targeting trnH-psbA and matK genes and identified host plants of field-collected Afro-tropical mosquito vectors of dengue, Rift Valley fever and malaria being among the most important mosquito-borne diseases in East Africa. These included three plant species for Aedes aegypti (dengue), two for both Aedes mcintoshi and Aedes ochraceus (Rift Valley fever) and five for Anopheles gambiae (malaria). Since plant feeding is mediated by olfactory cues, we further sought to identify specific odor signatures that may modulate host plant location. Using coupled gas chromatography (GC)-electroantennographic detection, GC/mass spectrometry and electroantennogram analyses, we identified a total of 21 antennally-active components variably detected by Ae. aegypti, Ae. mcintoshi and An. gambiae from their respective host plants. Whereas Ae. aegypti predominantly detected benzenoids, Ae. mcintoshi detected mainly aldehydes while An. gambiae detected sesquiterpenes and alkenes. Interestingly, the monoterpenes β-myrcene and (E)-β-ocimene were consistently detected by all the mosquito species and present in all the identified host plants, suggesting that they may serve as signature cues in plant location. This study highlights the utility of molecular approaches in identifying specific vector-plant associations, which can be exploited in maximizing control strategies such as such as attractive toxic sugar bait and odor-bait technology.

Turning workers into false queens– the role of exogenous pheromones in regulating reproduction in worker honey bees

One of the responses that honey bee workers can make in the event of queen loss is to develop into false queens. False queens are workers that exhibit both behavioural and physiological traits similar to those of a true queen. However, the presence of more than one false queen in a colony distorts the established hierarchies. As transformation into a false queen occurs after emergence as an adult, we tested the effect of worker mobile pheromone carriers (PCs) treated with exogenously supplied pheromones on their nestmates. The PCs carried either synthetic mandibular gland pheromones or pheromones extracted from capensis parasitic workers. Only PCs attracted retinues of workers, increased pheromone production, and activated their ovaries becoming false queens. Pheromones from capensis workers were more effective than extracts of commercially available synthetic queen pheromones in eliciting these effects. Using this simple mobile pheromone delivery system, we have shown that, carrying amounts of exogenous pheromone can induce pheromone production in the carrier resulting in the production of false queens within experimental groups. Possible implications of using this technique to modify and regulate worker reproduction in colonies are discussed.

Glandular sources of pheromones used to control host workers (Apis mellifera scutellata) by socially parasitic workers of Apis mellifera capensis

Pheromonal control by the honey bee queen is achieved through the use of secretions from diverse glandular sources, but the use of pheromones from a variety of glandular sources by reproductively dominant workers, has not previously been explored. Using the social parasite, Apis mellifera capensis clonal worker we studied the diversity of glandular sources used for pheromonal control of reproductively subordinate A. m. scutellata workers. To determine whether pheromones from different glandular sources are used by reproductively active workers to achieve dominance and evaluate the degree of pheromonal competition between workers of the two sub-species, we housed groups of workers of the two sub-species together in cages and analysed mandibular and tergal gland secretions as well as, ovarian activation status of each worker after 21days. The results showed that A. m. capensis invasive clones used both mandibular and tergal gland secretions to achieve reproductive dominance and suppress ovarian activation in their A. m. scutellata host workers. The reproductively dominant workers (false queens) produced more queen-like pheromones and inhibited ovarian activation in subordinate A. m. scutellata workers. These results show that tergal gland pheromones working in synergy with pheromones from other glands allow individual workers (false queens) to establish reproductive dominance within these social groups and to act in a manner similar to that of queens. Thus suggesting that, the evolution of reproductively dominant individuals (queens or false queens) and subordinate individuals (workers) in social insects like the honey bee is the result of a complex interplay of pheromonal signals from different exocrine glands.

Hygienic and grooming behaviors in African and European honeybees-New damage categories in Varroa destructor

Varroa destructor is an ectoparasitic pest of honeybees, and a threat to the survival of the apiculture industry. Several studies have shown that unlike European honeybees, African honeybee populations appear to be minimally affected when attacked by this mite. However, little is known about the underlying drivers contributing to survival of African honeybee populations against the mite. We hypothesized that resistant behavioral defenses are responsible for the survival of African honeybees against the ectoparasite. We tested this hypothesis by comparing grooming and hygienic behaviors in the African savannah honeybee Apis mellifera scutellata in Kenya and A. mellifera hybrids of European origin in Florida, USA against the mite. Grooming behavior was assessed by determining adult mite infestation levels, daily mite fall per colony and percentage mite damage (as an indicator of adult grooming rate), while hygienic behavior was assessed by determining the brood removal rate after freeze killing a section of the brood. Our results identified two additional undescribed damaged mite categories along with the six previously known damage categories associated with the grooming behavior of both honeybee subspecies. Adult mite infestation level was approximately three-fold higher in A. mellifera hybrids of European origin than in A. m. scutellata, however, brood removal rate, adult grooming rate and daily natural mite fall were similar in both honeybee subspecies. Unlike A. mellifera hybrids of European origin, adult grooming rate and brood removal rate did not correlate with mite infestation levels on adult worker honeybee of A. m. scutellata though they were more aggressive towards the mites than their European counterparts. Our results provide valuable insights into the tolerance mechanisms that contribute to the survival of A. m. scutellata against the mite.

Effect of Brood Pheromone on Survival and Nutrient Intake of African Honey Bees (Apis mellifera scutellata) under Controlled Conditions

The influence of pheromones on insect physiology and behavior has been thoroughly reported for numerous aspects, such as attraction, gland development, aggregation, mate and kin recognition. Brood pheromone (BP) is released by honey bee larvae to indicate their protein requirements to the colony. Although BP is known to modulate pollen and protein consumption, which in turn can affect physiological and morphological parameters, such as hypopharyngeal gland (HPG) development and ovarian activation, few studies have focused on the effect of BP on nutritional balance. In this study, we exposed newly emerged worker bees for 14 d and found that BP exposure increased protein intake during the first few days, with a peak in consumption at day four following exposure. BP exposure decreased survival of caged honey bees, but did not affect either the size of the HPG acini or ovarian activation stage. The uncoupling of the BP releaser effect, facilitated by working under controlled conditions, and the presence of larvae as stimulating cues are discussed.

The metabolic fate of nectar nicotine in worker honey bees

Honey bees (Apis mellifera) are generalist pollinators that forage for nectar and pollen of a very large variety of plant species, exposing them to a diverse range of secondary metabolites produced as chemical defences against herbivory. Honey bees can tolerate high levels of many of these toxic compounds, including the alkaloid nicotine, in their diet without incurring apparent fitness costs. Very little is known about the underlying detoxification processes mediating this tolerance. We examined the metabolic fate of nicotine in newly emerged worker bees using radiolabeled nicotine and LC-MS/MS analysis to determine the kinetic distribution profile of nicotine as well as the absence or presence and identity of any nicotine-derived metabolites. Nicotine metabolism was extensive; virtually no unmetabolised nicotine were recovered from the rectum. The major metabolite found was 4-hydroxy-4-(3-pyridyl) butanoic acid, the end product of 2'C-oxidation of nicotine. It is the first time that 4-hydroxy-4-(3-pyridyl) butanoic acid has been identified in an insect as a catabolite of nicotine. Lower levels of cotinine, cotinine N-oxide, 3'hydroxy-cotinine, nicotine N-oxide and norcotinine were also detected. Our results demonstrated that formation of 4-hydroxy-4-(3-pyridyl) butanoic acid is quantitatively the most significant pathway of nicotine metabolism in honey bees and that the rapid excretion of unmetabolised nicotine does not contribute significantly to nicotine tolerance in honey bees. In nicotine-tolerant insects that do not rely on the rapid excretion of nicotine like the Lepidoptera, it is possible that the 2'C-oxidation of nicotine is the conserved metabolic pathway instead of the generally assumed 5'C-oxidation pathway.

Proteomic and metabolomic analysis reveals rapid and extensive nicotine detoxification ability in honey bee larvae

Despite potential links between pesticides and bee declines, toxicology information on honey bee larvae (Apis mellifera) is scarce and detoxification mechanisms in this development stage are virtually unknown. Larvae are exposed to natural and synthetic toxins present in pollen and nectar through consumption of brood food. Due to the characteristic intensive brood care displayed by honey bees, which includes progressive feeding throughout larval development, it is generally assumed that larvae rely on adults to detoxify for them and exhibit a diminished detoxification ability. We found the opposite. We examined the proteomic and metabolomic responses of in vitro reared larvae fed nicotine (an alkaloid found in nectar and pollen) to understand how larvae cope on a metabolic level with dietary toxins. Larvae were able to effectively detoxify nicotine through an inducible detoxification mechanism. A coordinated stress response complemented the detoxification processes, and we detected significant enrichment of proteins functioning in energy and carbohydrate metabolism, as well as in development pathways, suggesting that nicotine may promote larval growth. Further exploration of the metabolic fate of nicotine using targeted mass spectrometry analysis demonstrated that, as in adult bees, formation of 4-hydroxy-4-(3-pyridyl) butanoic acid, the result of 2'C-oxidation of nicotine, is quantitatively the most significant pathway of nicotine metabolism. We provide conclusive evidence that larvae are capable of effectively catabolising a dietary toxin, suggesting that increased larval sensitivity to specific toxins is not due to diminished detoxification abilities. These findings broaden the current understanding of detoxification biochemistry at different organizational levels in the colony, bringing us closer to understanding the capacity of the colony as a superorganism to tolerate and resist toxic compounds, including pesticides, in the environment.

Effects of a neonicotinoid pesticide on thermoregulation of African honey bees (Apis mellifera scutellata)

Thiamethoxam is a widely used neonicotinoid pesticide that, as agonist of the nicotinic acetylcholine receptors, has been shown to elicit a variety of sublethal effects in honey bees. However, information concerning neonicotinoid effects on honey bee thermoregulation is lacking. Thermoregulation is an essential ability for the honey bee that guarantees the success of foraging and many in-hive tasks, especially brood rearing. We tested the effects of acute exposure to thiamethoxam (0.2, 1, 2ng/bee) on the thorax temperatures of foragers exposed to low (22°C) and high (33°C) temperature environments. Thiamethoxam significantly altered honey bee thorax temperature at all doses tested; the effects elicited varied depending on the environmental temperature and pesticide dose to which individuals were exposed. When bees were exposed to the high temperature environment, the high dose of thiamethoxam increased their thorax temperature 1-2h after exposure. When bees were exposed to the low temperature, the higher doses of the neonicotinoid reduced bee thorax temperatures 60-90min after treatment. In both experiments, the neonicotinoid decreased the temperature of bees the day following the exposure. After a cold shock (5min at 4°C), the two higher doses elicited a decrease of the thorax temperature, while the lower dose caused an increase, compared to the control. These alterations in thermoregulation caused by thiamethoxam may affect bee foraging activity and a variety of in-hive tasks, likely leading to negative consequences at the colony level. Our results shed light on sublethal effect of pesticides which our bees have to deal with.

Sucrose Sensitivity of Honey Bees Is Differently Affected by Dietary Protein and a Neonicotinoid Pesticide

Over a decade, declines in honey bee colonies have raised worldwide concerns. Several potentially contributing factors have been investigated, e.g. parasites, diseases, and pesticides. Neonicotinoid pesticides have received much attention due to their intensive use in crop protection, and their adverse effects on many levels of honey bee physiology led the European Union to ban these compounds. Due to their neuronal target, a receptor expressed throughout the insect nervous system, studies have focused mainly on neuroscience and behaviour. Through the Geometric Framework of nutrition, we investigated effects of the neonicotinoid thiamethoxam on survival, food consumption and sucrose sensitivity of honey bees (Apis mellifera). Thiamethoxam did not affect protein and carbohydrate intake, but decreased responses to high concentrations of sucrose. Interestingly, when bees ate fixed unbalanced diets, dietary protein facilitated better sucrose detection. Both thiamethoxam and dietary protein influenced survival. These findings suggest that, in the presence of a pesticide and unbalanced food, honey bee health may be severely challenged. Consequences for foraging efficiency and colony activity, cornerstones of honey bee health, are also discussed.

High Royal Jelly-Producing Honeybees (Apis mellifera ligustica) (Hymenoptera: Apidae) in China

China is the largest producer and exporter of royal jelly (RJ) in the world, supplying >90% of the global market. The high production of RJ in China is principally owing to the high RJ-producing lineage of honeybees (Apis mellifera ligustica Spinola, 1806) established by beekeepers in the 1980s. We describe the development of high royal jelly-producing honeybees and the management of this lineage today. Previous research and recent advances in the genetic characterization of this lineage, and the molecular markers and mechanisms associated with high RJ production are summarized. The gaps in our knowledge and prospects for future research are also highlighted.

Performance of pairwise shape dissimilarity morphometrics on nonmammalian taxa (Insecta: Neuroptera: Mantispidae)

Morphometric dissimilarity metrics aim to quantify the variation between compared specimens such that inferences about their relatedness and alpha taxonomy can be made. Recently, the technique has developed metrics that purport to quantify shape dissimilarity between specimens-employing the use of least squares regression analysis. These metrics have been well applied by studies in the hominin fossil record with an arguably unsubstantiated backing for the technique. Originally postulated was the log10 sem metric which subsequently led to the standard error test of the null hypothesis metric. Following this, the standard deviation of logged ratios (SLR ) metric arose as a pairwise dissimilarity metric that constrains the regression to a zero-intercept, that is, a significant development in the robustness of the technique. This metric was tested on extant primates in order to evaluate its effectiveness alongside the two other metrics. It was shown to be the most reliable for comparisons between specimens of primates, but was unable to discriminate between heterospecific and conspecific comparisons. Arguably, an alternative model organism with which to compare the technique is lacking. This study considers shape dissimilarity metrics with respect to a group of nonmammalian organisms (mantidflies) and tests the metrics against three lines of evidence (morphology, CO1-DNA, and geographic distribution) that can delimit the species-level taxonomy for the group. It is shown that the metrics are unable to discriminate between pairwise comparisons of closely related species, resulting in biologically erroneous groupings, and contradicting the groupings derived from morphological, CO1-DNA, and distributional comparisons. It is thus asserted that the technique is unsuitable for use in alpha taxonomy as an additional line of evidence in mantidflies. It is further supposed that morphometrics in general should be employed with caution in studies of evolutionary history as phylogeny is not the only information contained within morphometric data.

Hit-and-run trophallaxis of small hive beetles

Some parasites of social insects are able to exploit the exchange of food between nestmates via trophallaxis, because they are chemically disguised as nestmates. However, a few parasites succeed in trophallactic solicitation although they are attacked by workers. The underlying mechanisms are not well understood. The small hive beetle (=SHB), Aethina tumida, is such a parasite of honey bee, Apis mellifera, colonies and is able to induce trophallaxis. Here, we investigate whether SHB trophallactic solicitation is innate and affected by sex and experience. We quantified characteristics of the trophallactic solicitation in SHBs from laboratory‐reared individuals that were either bee‐naïve or had 5 days experience. The data clearly show that SHB trophallactic solicitation is innate and further suggest that it can be influenced by both experience and sex. Inexperienced SHB males begged more often than any of the other groups had longer breaks than their experienced counterparts and a longer soliciting duration than both experienced SHB males and females, suggesting that they start rather slowly and gain more from experience. Successful experienced females and males were not significantly different from each other in relation to successful trophallactic interactions, but had a significantly shorter soliciting duration compared to all other groups, except successful inexperienced females. Trophallactic solicitation success, feeding duration and begging duration were not significantly affected by either SHB sex or experience, supporting the notion that these behaviors are important for survival in host colonies. Overall, success seems to be governed by quality rather than quantity of interactions, thereby probably limiting both SHB energy investment and chance of injury (<1%). Trophallactic solicitation by SHBs is a singular example for an alternative strategy to exploit insect societies without requiring chemical disguise. Hit‐and‐run trophallaxis is an attractive test system to get an insight into trophallaxis in the social insects.

Effects of age and Reproductive Status on Tergal Gland Secretions in Queenless Honey bee Workers, Apis mellifera scutellata and A. m. capensis

Secretions from tergal glands are part of a queen's pheromonal control of worker reproduction in honey bees. However, in queenless honey bee colonies, workers compete to gain pheromonal, and hence reproductive dominance, over nestmates with ontogenetic changes in their glandular secretions that affect the behavioral or physiological responses of other individuals. Using gas chromatography/mass spectrometry, we investigated for the first time the age-dependent changes in tergal gland secretions of queenless workers of the clonal lineage of Apis mellifera capensis and workers of A. m. scutellata. The reproductive status of honey bee workers was determined by recording the presence of spermathecae and the level of ovarian activation. The tergal gland chemicals identified in both A. m. scutellata workers and A. m. capensis clone workers were oleic acid, n-tricosene, n-pentacosene, and n-heptacosene, with three additional compounds, palmitic acid, n-heneicosene, and n-nonacosene, in A. m. capensis clones. We report ethyl esters as new compounds from honey bee worker tergal gland profiles; these compounds increased in amount with age. All A. m. capensis clone workers dissected had spermathecae and showed ovarian activation from day 4, while ovarian activation only started on day 7 for A. m. scutellata workers that had no spermathecae. Tergal gland secretions were present in higher quantities in bees with activated, rather than inactive ovaries. This suggests that tergal gland secretions from reproductive workers could act as releaser and primer pheromones in synergy with other glandular compounds to achieve pheromonal and reproductive dominance.

Detoxification mechanisms of honey bees (Apis mellifera) resulting in tolerance of dietary nicotine

Insecticides are thought to be among the major factors contributing to current declines in bee populations. However, detoxification mechanisms in healthy, unstressed honey bees are poorly characterised. Alkaloids are naturally encountered in pollen and nectar, and we used nicotine as a model compound to identify the mechanisms involved in detoxification processes in honey bees. Nicotine and neonicotinoids have similar modes of action in insects. Our metabolomic and proteomic analyses show active detoxification of nicotine in bees, associated with increased energetic investment and also antioxidant and heat shock responses. The increased energetic investment is significant in view of the interactions of pesticides with diseases such as Nosema spp which cause energetic stress and possible malnutrition. Understanding how healthy honey bees process dietary toxins under unstressed conditions will help clarify how pesticides, alone or in synergy with other stress factors, lead to declines in bee vitality.

Impact of Varroa destructor on honeybee (Apis mellifera scutellata) colony development in South Africa

The devastating effects of Varroa destructor Anderson & Trueman on European honeybee colonies (Apis mellifera L.) have been well documented. Not only do these mites cause physical damage to parasitised individuals when they feed on them, they also transmit viruses and other pathogens, weaken colonies and can ultimately cause their death. Nevertheless, not all honeybee colonies are doomed once Varroa mites become established. Some populations, such as the savannah honeybee, A. m. scutellata, have become tolerant after the introduction of the parasite and are able to withstand the presence of these mites without the need for acaricides. In this study, we measured daily Varroa mite fall, Varroa infestation rates of adult honeybees and worker brood, and total Varroa population size in acaricide treated and untreated honeybee colonies. In addition, honeybee colony development was compared between these groups in order to measure the cost incurred by Varroa mites to their hosts. Daily Varroa mite fall decreased over the experimental period with different dynamics in treated and untreated colonies. Varroa infestation rates in treated adult honeybees and brood were lower than in untreated colonies, but not significantly so. Thus, indicating a minimal benefit of treatment thereby suggesting that A. m. scutellata have the ability to maintain mite populations at low levels. We obtained baseline data on Varroa population dynamics in a tolerant honeybee over the winter period. Varroa mites appeared to have a low impact on this honeybee population, given that colony development was similar in the treated and untreated colonies.