Patterns of feeding behaviour in adult male riodinid butterflies and their relationship to morphology and ecology

Phylogenomics of the Ecdysteroid Kinase-like (EcKL) Gene Family in Insects Highlights Roles in Both Steroid Hormone Metabolism and Detoxification

The evolutionary dynamics of large gene families can offer important insights into the functions of their individual members. While the ecdysteroid kinase-like (EcKL) gene family has previously been linked to the metabolism of both steroid molting hormones and xenobiotic toxins, the functions of nearly all EcKL genes are unknown, and there is little information on their evolution across all insects. Here, we perform comprehensive phylogenetic analyses on a manually annotated set of EcKL genes from 140 insect genomes, revealing the gene family is comprised of at least 13 subfamilies that differ in retention and stability. Our results show the only two genes known to encode ecdysteroid kinases belong to different subfamilies and therefore ecdysteroid metabolism functions must be spread throughout the EcKL family. We provide comparative phylogenomic evidence that EcKLs are involved in detoxification across insects, with positive associations between family size and dietary chemical complexity, and we also find similar evidence for the cytochrome P450 and glutathione S-transferase gene families. Unexpectedly, we find that the size of the clade containing a known ecdysteroid kinase is positively associated with host plant taxonomic diversity in Lepidoptera, possibly suggesting multiple functional shifts between hormone and xenobiotic metabolism. Our evolutionary analyses provide hypotheses of function and a robust framework for future experimental studies of the EcKL gene family. They also open promising new avenues for exploring the genomic basis of dietary adaptation in insects, including the classically studied coevolution of butterflies with their host plants.

Co-modulation of structural and pigmentary coloration in Lyropteryx apollonia butterfly

Nature produces some of the most striking optical effects through the combination of structural and chemical principles to give rise to a wide range of colors. However, creating non-spectral colors that extend beyond the color spectrum is a challenging task, as it requires meeting the requirements of both structural and pigmentary coloration. In this study, we investigate the magenta non-spectral color found in the scales of the ventral spots of the Lyropteryx apollonia butterfly. By employing correlated optical and electron microscopy, as well as pigment extraction techniques, we reveal how this color arises from the co-modulation of pigmentary and structural coloration. Specifically, the angle-dependent blue coloration results from the interference of visible light with chitin-based nanostructures, while the diffused red coloration is generated by an ommochrome pigment. The ability to produce such highly conspicuous non-spectral colors provides insights for the development of hierarchical structures with precise control over their optical response. These structures can be used to create hierarchically-arranged systems with a broadened color palette.

Amazonian Odonata Trait Bank

Discussion regarding the gaps of knowledge on Odonata is common in the literature. Such gaps are even greater when dealing with basic biological data for biodiverse environments like the Amazon Rainforest. Therefore, studies that address, classify, and standardize functional traits allow the elaboration of a wide range of ecological and evolutionary hypotheses. Moreover, such endeavors aid conservation and management planning by providing a better understanding of which functional traits are filtered or favored under environmental changes. Here, our main goal was to produce a database with 68 functional traits of 218 Odonata species that occur in the Brazilian Amazon. We extracted data on behavior, habit/habitat (larvae and adults), thermoregulation, and geographic distribution from 419 literature sources classified into different research areas. Moreover, we measured 22 morphological traits of approximately 2500 adults and categorized species distributions based on approximately 40,000 geographic records for the Americas. As a result, we provided a functional matrix and identified different functional patterns for the Odonata suborders, as well as a strong relationship between the different trait categories. For this reason, we recommend the selection of key traits that represent a set of functional variables, reducing the sampling effort. In conclusion, we detect and discuss gaps in the literature and suggest research to be developed with the present Amazonian Odonata Trait Bank (AMO-TB).

Impact of environmental changes on the behavioral diversity of the Odonata (Insecta) in the Amazon

The odonates are insects that have a wide range of reproductive, ritualized territorial, and aggressive behaviors. Changes in behavior are the first response of most odonate species to environmental alterations. In this context, the primary objective of the present study was to assess the effects of environmental alterations resulting from shifts in land use on different aspects of the behavioral diversity of adult odonates. Fieldwork was conducted at 92 low-order streams in two different regions of the Brazilian Amazon. To address our main objective, we measured 29 abiotic variables at each stream, together with five morphological and five behavioral traits of the resident odonates. The results indicate a loss of behaviors at sites impacted by anthropogenic changes, as well as variation in some morphological/behavioral traits under specific environmental conditions. We highlight the importance of considering behavioral traits in the development of conservation strategies, given that species with a unique behavioral repertoire may suffer specific types of extinction pressure.

Forest stratification shapes allometry and flight morphology of tropical butterflies

Studies of altitudinal and latitudinal gradients have identified links between the evolution of insect flight morphology, landscape structure and microclimate. Although lowland tropical rainforests offer steeper shifts in conditions between the canopy and the understorey, this vertical gradient has received far less attention. Butterflies, because of their great phenotypic plasticity, are excellent models to study selection pressures that mould flight morphology. We examined data collected over 5 years on 64 Nymphalidae butterflies in the Ecuadorian Chocó rainforest. We used phylogenetic methods to control for similarity resulting from common ancestry, and explore the relationships between species stratification and flight morphology. We hypothesized that species should show morphological adaptations related to differing micro-environments, associated with canopy and understorey. We found that butterfly species living in each stratum presented significantly different allometric slopes. Furthermore, a preference for the canopy was significantly associated with low wing area to thoracic volume ratios and high wing aspect ratios, but not with the relative distance to the wing centroid, consistent with extended use of fast flapping flight for canopy butterflies and slow gliding for the understorey. Our results suggest that microclimate differences in vertical gradients are a key factor in generating morphological diversity in flying insects.

Intraspecific Variation in Nectar Chemistry and Its Implications for Insect Visitors: The Case of the Medicinal Plant, Polemonium Caeruleum L

Floral nectar, being a primary reward for insect visitors, is a key factor in shaping plant–pollinator interactions. However, little is known about the variability in nectar traits, which could potentially affect pollinators and the reproduction of the species. We investigated intraspecific variation in nectar traits in 14 populations of a Red-listed plant, Polemonium caeruleum. Populations varied in terms of the proportion of self-compatible and self-incompatible individuals, and insect communities visiting flowers. Using HPLC, we determined the nectar sugar and amino acid (AA) composition and concentration. We also recorded some basic habitat parameters, which could influence nectar chemistry. In seven selected populations, we investigated the taxonomic composition of the insects visiting flowers. Our observations revealed significant intraspecific variability in nectar chemistry in P. caeruleum. Nectar production was male-biased, with male-phase flowers secreting sucrose- and AA-rich nectar. An analysis revealed that variability in P. caeruleum nectar may be slightly shaped by environmental factors. The studied nectar characters, especially sugars, had little effect on insects visiting flowers. We argue that variation in nectar traits in this generalist plant is a matter of random genetic drift or “adaptive wandering” rather than directional specialization and adaptation in the most effective and abundant group of pollinators.

Adaptive evolution of butterfly wing shape: from morphology to behaviour

Butterflies display extreme variation in wing shape associated with tremendous ecological diversity. Disentangling the role of neutral versus adaptive processes in wing shape diversification remains a challenge for evolutionary biologists. Ascertaining how natural selection influences wing shape evolution requires both functional studies linking morphology to flight performance, and ecological investigations linking performance in the wild with fitness. However, direct links between morphological variation and fitness have rarely been established. The functional morphology of butterfly flight has been investigated but selective forces acting on flight behaviour and associated wing shape have received less attention. Here, we attempt to estimate the ecological relevance of morpho-functional links established through biomechanical studies in order to understand the evolution of butterfly wing morphology. We survey the evidence for natural and sexual selection driving wing shape evolution in butterflies, and discuss how our functional knowledge may allow identification of the selective forces involved, at both the macro- and micro-evolutionary scales. Our review shows that although correlations between wing shape variation and ecological factors have been established at the macro-evolutionary level, the underlying selective pressures often remain unclear. We identify the need to investigate flight behaviour in relevant ecological contexts to detect variation in fitness-related traits. Identifying the selective regime then should guide experimental studies towards the relevant estimates of flight performance. Habitat, predators and sex-specific behaviours are likely to be major selective forces acting on wing shape evolution in butterflies. Some striking cases of morphological divergence driven by contrasting ecology involve both wing and body morphology, indicating that their interactions should be included in future studies investigating co-evolution between morphology and flight behaviour.

Effects of natural wing damage on flight performance in Morpho butterflies: what can it tell us about wing shape evolution?

Flying insects frequently experience wing damage during their life. Such irreversible alterations of wing shape affect flight performance and ultimately fitness. Insects have been shown to compensate for wing damage through various behavioural adjustments, but the importance of damage location over the wings has been scarcely studied. Using natural variation in wing damage, here we tested how the loss of different wing parts affect flight performance. We quantified flight performance in two species of large butterflies, Morpho helenor and M. achilles, caught in the wild, and displaying large variation in the extent and location of wing damage. We artificially generated more severe wing damage in our sample to contrast natural vs. higher magnitude of wing loss. Wing shape alteration across our sample was quantified using geometric morphometrics to test the effect of different damage distributions on flight performance. Our results show that impaired flight performance clearly depends on damage location over the wings, pointing out a relative importance of different wing parts for flight. Deteriorated forewings leading edge most crucially affected flight performance, specifically decreasing flight speed and proportion of gliding flight. In contrast, most frequent natural damage such as scattered wing margin had no detectable effect on flight behaviour. Damages located on the hindwings – although having a limited effect on flight – were associated with reduced flight height, suggesting that fore- and hindwings play different roles in butterfly flight. By contrasting harmless and deleterious consequences of various types of wing damage, our study points at different selective regimes acting on morphological variations of butterfly wings.

Dietary and developmental shifts in butterfly-associated bacterial communities

Bacterial communities associated with insects can substantially influence host ecology, evolution and behaviour. Host diet is a key factor that shapes bacterial communities, but the impact of dietary transitions across insect development is poorly understood. We analysed bacterial communities of 12 butterfly species across different developmental stages, using amplicon sequencing of the 16S rRNA gene. Butterfly larvae typically consume leaves of a single host plant, whereas adults are more generalist nectar feeders. Thus, we expected bacterial communities to vary substantially across butterfly development. Surprisingly, only few species showed significant dietary and developmental transitions in bacterial communities, suggesting weak impacts of dietary transitions across butterfly development. On the other hand, bacterial communities were strongly influenced by butterfly species and family identity, potentially due to dietary and physiological variation across the host phylogeny. Larvae of most butterfly species largely mirrored bacterial community composition of their diets, suggesting passive acquisition rather than active selection. Overall, our results suggest that although butterflies harbour distinct microbiomes across taxonomic groups and dietary guilds, the dramatic dietary shifts that occur during development do not impose strong selection to maintain distinct bacterial communities across all butterfly hosts.

Coevolution between flight morphology, vertical stratification and sexual dimorphism: what can we learn from tropical butterflies?

Occurrence patterns are partly shaped by the affinity of species with habitat conditions. For winged organisms, flight-related attributes are vital for ecological performance. However, due to the different reproductive roles of each sex, we expect divergence in flight energy budget, and consequently different selection responses between sexes. We used tropical frugivorous butterflies as models to investigate coevolution between flight morphology, sex dimorphism and vertical stratification. We studied 94 species of Amazonian fruit-feeding butterflies sampled in seven sites across 3341 ha. We used wing-thorax ratio as a proxy for flight capacity and hierarchical Bayesian modelling to estimate stratum preference. We detected a strong phylogenetic signal in wing-thorax ratio in both sexes. Stouter fast-flying species preferred the canopy, whereas more slender slow-flying species preferred the understorey. However, this relationship was stronger in females than in males, suggesting that female phenotype associates more intimately with habitat conditions. Within species, males were stouter than females and sexual dimorphism was sharper in understorey species. Because trait-habitat relationships were independent from phylogeny, the matching between flight morphology and stratum preference is more likely to reflect adaptive radiation than shared ancestry. This study sheds light on the impact of flight and sexual dimorphism on the evolution and ecological adaptation of flying organisms.

Effects of sodium puddling on male mating success, courtship and flight in a swallowtail butterfly

In many Lepidoptera species usually only males puddle for sodium. Two explanations have been offered for this: (1) neuromuscular activity: males need increased sodium for flight because they are more active flyers than females; and (2) direct benefits: sodium is a type of direct benefit provided by males to females via ejaculate during mating. Surprisingly, there is little direct experimental evidence for either of these. In this study, we examined both explanations using the pipevine swallowtail butterfly, Battus philenor L. If sodium increases neuromuscular activity, males consuming sodium should be better fliers than males without sodium. If males collect sodium for nuptial gifts that benefit their mates, males consuming sodium may have greater mating success than males without sodium. In that case, females then need an honest cue/signal of the quality of male-provided direct benefits that they can assess before mating. If sodium affects male courtship flight by increasing neuromuscular activity, how a male courts could serve as such a premating cue/signal of male benefit quality. Therefore, sodium may benefit males in terms of obtaining mates by increasing their neuromuscular activity. In this study we found that males that consumed sodium courted more vigorously and had greater mating success than males that consumed water. In addition, the courtship displays of males consuming sodium were significantly different from those of males consuming water, providing a possible honest cue/signal of male benefit quality that females can assess. Interestingly, we did not find evidence that sodium consumption affects male flight outside of courtship. That only aspects of male flight related to mating were affected by sodium, while aspects of general flight were not, is consistent with the idea that sodium may benefit males in terms of obtaining mates via effects on neuromuscular activity.

Past Human Disturbance Effects upon Biodiversity are Greatest in the Canopy; A Case Study on Rainforest Butterflies

A key part of tropical forest spatial complexity is the vertical stratification of biodiversity, with widely differing communities found in higher rainforest strata compared to terrestrial levels. Despite this, our understanding of how human disturbance may differentially affect biodiversity across vertical strata of tropical forests has been slow to develop. For the first time, how the patterns of current biodiversity vary between three vertical strata within a single forest, subject to three different types of historic anthropogenic disturbance, was directly assessed. In total, 229 species of butterfly were detected, with a total of 5219 individual records. Butterfly species richness, species diversity, abundance and community evenness differed markedly between vertical strata. We show for the first time, for any group of rainforest biodiversity, that different vertical strata within the same rainforest, responded differently in areas with different historic human disturbance. Differences were most notable within the canopy. Regenerating forest following complete clearance had 47% lower canopy species richness than regenerating forest that was once selectively logged, while the reduction in the mid-storey was 33% and at ground level, 30%. These results also show for the first time that even long term regeneration (over the course of 30 years) may be insufficient to erase differences in biodiversity linked to different types of human disturbance. We argue, along with other studies, that ignoring the potential for more pronounced effects of disturbance on canopy fauna, could lead to the underestimation of the effects of habitat disturbance on biodiversity, and thus the overestimation of the conservation value of regenerating forests more generally.

Functional constraints on the evolution of long butterfly proboscides: lessons from Neotropical skippers (Lepidoptera: Hesperiidae)

Extremely long proboscides are rare among butterflies outside of the Hesperiidae, yet representatives of several genera of skipper butterflies possess proboscides longer than 50 mm. Although extremely elongated mouthparts can be regarded as advantageous adaptations to gain access to nectar in deep-tubed flowers, the scarcity of long-proboscid butterflies is a phenomenon that has not been adequately accounted for. So far, the scarceness was explained by functional costs arising from increased flower handling times caused by decelerated nectar intake rates. However, insects can compensate for the negative influence of a long proboscis through changes in the morphological configuration of the feeding apparatus. Here, we measured nectar intake rates in 34 species representing 21 Hesperiidae genera from a Costa Rican lowland rainforest area to explore the impact of proboscis length, cross-sectional area of the food canal and body size on intake rate. Long-proboscid skippers did not suffer from reduced intake rates due to their large body size and enlarged food canals. In addition, video analyses of the flower-visiting behaviour revealed that suction times increased with proboscis length, suggesting that long-proboscid skippers drink a larger amount of nectar from deep-tubed flowers. Despite these advantages, we showed that functional costs of exaggerated mouthparts exist in terms of longer manipulation times per flower. Finally, we discuss the significance of scaling relationships on the foraging efficiency of butterflies and why some skipper taxa, in particular, have evolved extremely long proboscides.

Four Forensic Entomology Case Studies: Records and Behavioral Observations on Seldom Reported Cadaver Fauna With Notes on Relevant Previous Occurrences and Ecology

A yearlong survey of insect taxa associated with human decomposition was conducted at the Southeast Texas Applied Forensic Science (STAFS) facility located in the Center for Biological Field Studies of Sam Houston State University in Huntsville, TX. During this study, four insect-cadaver interactions were observed that represent previously poorly documented yet forensically significant interactions: Syrphidae maggots colonized a corpse in an aquatic situation; Psychodidae adults mated and oviposited on an algal film that was present on a corpse that had been recently removed from water; several Panorpidae were the first insects to feed upon a freshly placed corpse in the autumn; and a noctuid caterpillar was found chewing and ingesting dried human skin. Baseline knowledge of insect-cadaver interactions is the foundation of forensic entomology, and unique observations have the potential to expand our understanding of decomposition ecology.

Anthropogenic changes in sodium affect neural and muscle development in butterflies

The development of organisms is changing drastically because of anthropogenic changes in once-limited nutrients. Although the importance of changing macronutrients, such as nitrogen and phosphorus, is well-established, it is less clear how anthropogenic changes in micronutrients will affect organismal development, potentially changing dynamics of selection. We use butterflies as a study system to test whether changes in sodium availability due to road salt runoff have significant effects on the development of sodium-limited traits, such as neural and muscle tissue. We first document how road salt runoff can elevate sodium concentrations in the tissue of some plant groups by 1.5-30 times. Using monarch butterflies reared on roadside- and prairie-collected milkweed, we then show that road salt runoff can result in increased muscle mass (in males) and neural investment (in females). Finally, we use an artificial diet manipulation in cabbage white butterflies to show that variation in sodium chloride per se positively affects male flight muscle and female brain size. Variation in sodium not only has different effects depending on sex, but also can have opposing effects on the same tissue: across both species, males increase investment in flight muscle with increasing sodium, whereas females show the opposite pattern. Taken together, our results show that anthropogenic changes in sodium availability can affect the development of traits in roadside-feeding herbivores. This research suggests that changing micronutrient availability could alter selection on foraging behavior for some roadside-developing invertebrates.

Functional morphology of the feeding apparatus and evolution of proboscis length in metalmark butterflies (Lepidoptera: Riodinidae)

An assessment of the anatomical costs of extremely long proboscid mouthparts can contribute to the understanding of the evolution of form and function in the context of insect feeding behaviour. An integrative analysis of expenses relating to an exceptionally long proboscis in butterflies includes all organs involved in fluid feeding, such as the proboscis plus its musculature, sensilla, and food canal, as well as organs for proboscis movements and the suction pump for fluid uptake. In the present study, we report a morphometric comparison of derived long-tongued (proboscis approximately twice as long as the body) and short-tongued Riodinidae (proboscis half as long as the body), which reveals the non-linear scaling relationships of an extremely long proboscis. We found no elongation of the tip region, low numbers of proboscis sensilla, short sensilla styloconica, and no increase of galeal musculature in relation to galeal volume, but a larger food canal, as well as larger head musculature in relation to the head capsule. The results indicate the relatively low extra expense on the proboscis musculature and sensilla equipment but significant anatomical costs, such as reinforced haemolymph and suction pump musculature, as well as thick cuticular proboscis walls, which are functionally related to feeding performance in species possessing an extremely long proboscis. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 291–304.

Procurement of exogenous ammonia by the swallowtail butterfly, Papilio polytes, for protein biosynthesis and sperm production

How to acquire sufficient quantity of nitrogen is a pivotal issue for herbivores, particularly for lepidopterans (butterflies and moths) of which diet quality greatly differs among their life stages. Male Lepidoptera often feed from mud puddles, dung, and carrion, a behavior known as puddling, which is thought to be supplementary feeding targeted chiefly at sodium. During copulation, males transfer a spermatophore to females that contains, besides sperm, nutrients (nuptial gifts) rich in sodium, proteins, and amino acids. However, it is still poorly understood how adults, mostly nectarivores, extract nitrogen from the environment. We examined the availability of two ubiquitous inorganic nitrogenous ions in nature, viz. ammonium (or ammonia) and nitrate ions, as nutrients in a butterfly, and show that exogenous ammonia ingested by adult males of the swallowtail, Papilio polytes, can serve as a resource for protein biosynthesis. Feeding experiments with (15)N-labeled ammonium chloride revealed that nitrogen was incorporated into eupyrene spermatozoa, seminal protein, and thoracic muscle. Ammonia uptake by males significantly increased the number of eupyrene sperms in the reproductive tract tissues. The females also had the capacity to assimilate ammonia into egg protein. Consequently, it is evident that acquired ammonia is utilized for the replenishment of proteins allocable for reproduction and somatic maintenance. The active exploitation of exogenous ammonia as a nutrient by a butterfly would foster better understanding of the foraging and reproductive strategies in insects.

Effects of dietary sodium on performance, flight and compensation strategies in the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

BACKGROUND

Sodium is critical for many physiological functions in insects. Herbivorous insects should expend considerable energy to compensate for sodium deficiency due to low sodium concentration in most inland plants upon which they feed. However, sodium compensation behaviors such as mud-puddling have been observed in some species but not in others. We expect that there may be other sodium compensation strategies in insects. Here, we select a rarely mud-puddling insect species, the cotton boll worm, Helicoverpa armigera, and determine the effects of dietary sodium on performance and flight, and examine their means of sodium compensation.

RESULTS

When freshly hatched H. armigera neonates were cultured on one of three diets differing in sodium contents (diet A, B and C with a high, middle and low sodium concentrations, respectively), the larvae on diet C grew larger, had a higher mortality rate and a shorter development period than those on diet A and B. The larvae previously fed from 1st to 3rd instar on diet C consumed more subsequent diet when they were transferred to diet A or C at 4th instar, comparing to those previously fed on diet A. Moreover, any 4th-instar larvae on diet C consumed a greater amount of food than those on diet A, no matter which diet the larvae had previously ingested from 1st to 3rd instar. Moths from diet A and B flew more rapidly than those from diet C, with similar sugar and lipid utilization rates among the three test groups. When a 5th-instar cannibal from diet A, B or C and a 5th-instar victim from diet A were housed together, many more cannibals from diet C ate their victims. When a victim from diet A, B or C was provided, a cannibal from diet C was more likely to eat the victim from diet A. When newly emerged moths had been exposed to 3% sodium chloride solution for all scotophase period, the average weight increase (proxy for sodium solution intake) for moths from diet A was lower than those from diet B or C.

CONCLUSION

Sodium-deficient diet resulted in rapid growth and development of H. armigera larvae, decreased larvae survival, and reduced flight speed of H. armigera adults. To compensate for sodium deficiency, H. armigera ingested a large quantity of larval food, increased larval cannibalism incidence and harvested sodium during the adult stage.

Mud-puddling in the yellow-spined bamboo locust, Ceracris kiangsu (Oedipodidae: Orthoptera): does it detect and prefer salts or nitrogenous compounds from human urine?

C. kiangsu adults were observed visiting human urine, especially on hot summer days. The main chemicals in fresh human urine include inorganic salts and CO(NH(2))(2.) When human urine was incubated, NH(4)HCO(3) became the richest nitrogenous compound. The phagostimulants, repellents and attractants in urine were identified here. On the filter papers treated with fresh or incubated urine samples, the 5th instar nymphs and the adults started and continued gnawing around the edges, in contrast to the 3rd and the 4th instar nymphs. The consumed areas were dramatically greater on the filters treated with the urine samples incubated for 3-6 days. The feedings of both male and female adults were also stimulated by several urine-borne components such as NaCl, NaH(2)PO(4), Na(2)SO(4), KCl, NH(4)Cl and NH(4)HCO(3) but not by CO(NH(2))(2). Among them NaCl was the most powerful phagostimulant. The repelling, or attractive/arresting effects of CO(NH(2))(2) and NH(4)HCO(3) were also evaluated by a two-choice test. When exposed to water- and CO(NH(2))(2) solution-immersed filters simultaneously, the adults prefer to stay on water-immersed filter. In contrast, when provided water- and NH(4)HCO(3) solution-treated filters, the adults prefer to stay on NH(4)HCO(3) solution-treated filter. This demonstrated that CO(NH(2))(2) acted as a repellent and NH(4)HCO(3) as an attractant/arrestant. In the bamboo forest, similar feeding behavior was also elicited by NaCl, NH(4)HCO(3) but not by CO(NH(2))(2). Comparing to NaCl solution, a mixed solution of NaCl and CO(NH(2))(2) (1:1) significantly decreased the consumed area of the treated filters whereas a mixed solution of NaCl and NH(4)HCO(3) (1:1) dramatically increased the consumed area. These results demonstrated that the phagostimulatory effect by NaCl was reduced by CO(NH(2))(2) in fresh urine and was enhanced by NH(4)HCO(3) in incubated urine.

The Amino Acids Used in Reproduction by Butterflies: A Comparative Study of Dietary Sources Using Compound‐Specific Stable Isotope Analysis

It is a nutritional challenge for nectar-feeding insects to meet the amino acid requirements of oviposition. Here we investigate whether egg amino acids derive from larval diet or are synthesized from nectar sugar in four species of butterfly: Colias eurytheme, Speyeria mormonia, Euphydryas chalcedona, and Heliconius charitonia. These species exhibit a range of life history and differ in degree of shared phylogeny. We use 13C differences among plants to identify dietary sources of amino acid carbon, and we measure amino acid 13C using compound-specific stable isotope analysis. Egg essential amino acids derived solely from the larval diet, with no evidence for metabolic carbon remodeling. Carbon in nonessential amino acids from eggs derived primarily from nectar sugars, with consistent variation in amino acid turnover. There was no relationship between the nonessential amino acids of eggs and host plants, demonstrating extensive metabolic remodeling. Differences between species in carbon turnover were reflected at the molecular level, particularly by glutamate and aspartate. Essential amino acid 13C varied in a highly consistent pattern among larval host plants, reflecting a common isotopic "fingerprint" associated with plant biosynthesis. These data demonstrate conservative patterns of amino acid metabolism among Lepidoptera and the power of molecular stable isotope analyses for evaluating nutrient metabolism in situ.

Pollen feeding in the butterfly Heliconius charitonia: isotopic evidence for essential amino acid transfer from pollen to eggs

Heliconius and Laparus butterflies exhibit a unique pollen-collecting behaviour that enhances lifespan and fecundity. The specific nutritional contribution of pollen, however, had not been previously demonstrated. We used stable isotope variation to trace the carbon flow into eggs from corn pollen provided experimentally to ovipositing female Heliconius charitonia, and to evaluate the use of isotopically contrasting nectar sugars in egg amino acids. The delta(13)C of individual amino acids from pollen, larval host plant and the eggs from experimental butterflies was measured with gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), to evaluate amino acid transfer. The delta(13)C of egg essential amino acids indicated a transfer of essential amino acids from pollen to butterfly eggs. However, the delta(13)C of non-essential amino acids reflected the isotopic composition of the artificial nectar, indicating that H. charitonia synthesizes non-essential amino acids from dietary sugars. This, to our knowledge, is the first direct demonstration of amino acid transfer from pollen to butterfly eggs, and suggests that essential amino acids in particular are a key resource for extending lifespan and fecundity in Heliconius butterflies.

The ecology and evolution of ant association in the Lycaenidae (Lepidoptera)

The estimated 6000 species of Lycaenidae account for about one third of all Papilionoidea. The majority of lycaenids have associations with ants that can be facultative or obligate and range from mutualism to parasitism. Lycaenid larvae and pupae employ complex chemical and acoustical signals to manipulate ants. Cost/benefit analyses have demonstrated multiple trade-offs involved in myrmecophily. Both demographic and phylogenetic evidence indicate that ant association has shaped the evolution of obligately associated groups. Parasitism typically arises from mutualism with ants, and entomophagous species are disproportionately common in the Lycaenidae compared with other Lepidoptera. Obligate associations are more common in the Southern Hemisphere, in part because highly ant-associated lineages make up a larger proportion of the fauna in these regions. Further research on phylogeny and natural history, particularly of the Neotropical fauna, will be necessary to understand the role ant association has played in the evolution of the Lycaenidae.