Mothers modify eggs into shields to protect offspring from parasitism

Eggs are an immobile, vulnerable stage of development and their success often depends on the oviposition decisions of the mother. Studies show that female animals, and sometimes males, may invest parental resources in order to increase the survival of their offspring. Here, we describe a unique form of parental investment in offspring survival. The seed beetle Mimosestes amicus may lay eggs singly, or may cover eggs with additional egg(s). This egg stacking serves to significantly reduce the mortality of the protected egg from parasitism by the parasitic wasp, Uscana semifumipennis. The smaller top eggs serve only as protective shields; they are inviable, and wasps that develop in them suffer negative fitness consequences. Further, we found egg stacking to be inducible; M. amicus increase the number of stacks they lay when parasitoids are present. However, stacking invokes a cost. When wasps are absent, beetles lay more single eggs, and produce more offspring, highlighting the adaptive value of this extraordinary example of behavioural plasticity in parental investment.

Occurrence of Stiretrus decastigmus (Herrich-Schaeffer) (Hemiptera: Pentatomidae) preying on Microtheca semilaevis Stal (Coleoptera: Chrysomelidae)

Microtheca semilaevis Stal is a phythophagous insect associated to Brassicaceae, and frequently occurs with other species of beetles, such as Microtheca ochroloma Stal. Despite its importance to organic farmers, there is no information in the Brazilian literature about its natural enemies. Stiretrus decastigmus (Herrich-Schaeffer) was first found and here reported preying an adult of M. semilaevis in Chinese cabbage in Santa Maria, RS, Brazil (29°43'28″S, 53°43'19″W).

Sex, war, and disease: the role of parasite infection on weapon development and mating success in a horned beetle (Gnatocerus cornutus)

While parasites and immunity are widely believed to play important roles in the evolution of male ornaments, their potential influence on systems where male weaponry is the object of sexual selection is poorly understood. We experimentally infect larval broad-horned flour beetles with a tapeworm and study the consequent effects on: 1) adult male morphology 2) male-male contests for mating opportunities, and 3) induction of the innate immune system. We find that infection significantly reduces adult male size in ways that are expected to reduce mating opportunities in nature. The sum of our morphological, competition, and immunological data indicate that during a life history stage where no new resources are acquired, males allocate their finite resources in a way that increases future mating potential.

Efficiency of host utilisation by coleopteran parasitoid

In insect larvae, optimising food utilisation with respect to available meals and time is essential for achieving maximum adult body size, which is a relevant proxy of fitness. We studied the efficiency of food conversion, body size, mortality, and development time in a solitary idiobiont ectoparasitoid, Brachinus explodens (Coleoptera: Carabidae), reared in the laboratory on the pupae of another carabid genus, Amara. The efficiency of conversion index (ECI - ratio of ingested to assimilated food) was, on average, 54.1±1.1% (n=76), with a minimum of 26.9% and a maximum of 81.6%. The rate of increase in biomass gained (W(gained)) with biomass of the host was constant in females, but it decreased in males over the range of host body mass. Females, therefore, grew heavier from hosts of the same mass compared to males. Body length increased with the host mass and was correlated with W(gained) identically for both sexes. Mortality was unaffected by the host mass, but it significantly increased below 20°C. In contrast, the development time of the feeding phase of the larva increased with the host mass at 20.3 and 23.7°C, but it remained unaffected at 26.9°C and in all three temperatures considering pupal development. W(gained) increased with development time up to ca. 8 days of larval feeding at 23.7°C. To our knowledge, our data are the first on food utilisation in solitary idiobiont coleopteran ectoparasitoids, and they present the highest values of ECI in insects.

Biology, immature and adult morphology, and molecular characterization of a new species of the genus Entedon (Hymenoptera: Eulophidae) associated with the invasive pest Specularius impressithorax (Coleoptera: Chrysomelidae, Bruchinae) on Erythrina plants

Entedon erythrinae sp. n. (Hymenoptera: Eulophidae), a gregarious egg-larval endoparasitoid of the Erythrina bruchine Specularius impressithorax, an invasive pest of the coral tree seeds (Erythrina spp.), is described from the Hawaiian Islands and Africa (South Africa, Tanzania and Mozambique). The biology and morphology of preimaginal stages of this new species are described in details.It is remarkable that the early embryo of the parasitoid represents a mass of undifferentiated cells surrounded by a peculiar membrane formed by the peripheral enlarged polygonal cells. The young larva developing inside this membrane corresponds morphologically to the second instar of congeneric species. Various peculiarities of the parasitoid-host relationships in gregarious and solitary Entedon parasitoids are discussed. The DNA sequences of 28S D2 (nuclear), Cytochrome Oxidase I (COI, mitochondrial) and Cytochrome B (CytB, mitochondrial) genes are provided for this new species and compared with the sequences of some other Afrotropical and Palearctic species of the genus.

Record of Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) preying on Metrogaleruca obscura Degeer (Coleoptera: Chrysomelidae)

Asopines are predators of insects, with several species with potential as biocontrol agents of a number of pests. Metrogaleruca obscura (Degeer), a neotropical species of Galerucini, was introduced in Malaysia, Asia, and Mauritius, Africa, to control the spread of Cordia curassavica (Boraginaceae), a native plant of the neotropics. The occurrence of Podisus nigrispinus (Dallas) preying on M. obscura is recorded, and Cordia verbenacea (Boraginaceae) is mentioned as a host plant for M. obscura. A list of Chrysomelidae attacked by asopines in the neotropical region is also presented.

Host-size mediated trade-off in a parasitoid Sclerodermus harmandi

Optimality models of host-parasitoid relationships have traditionally assumed that host quality increases as a function of host size at parasitism. However, trade-offs may play a crucial role in species evolution and should be found in host-parasitoid interactions where the host quality may differ between different sizes. Here, we investigated the effects of host size differences of Monochamus alternatus larva on foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi. Two-choice and non-choice experiments were conducted with M. alternatus larvae to evaluate preference and performance of S. harmandi, respectively. Results from two-choice test showed that adult females prefer to attack large larvae rather than small larvae. In no-choice tests, adult females needed more time to paralyze large larvae than small larvae before laying eggs on the body surface of M. alternatus larvae and had lower survival and parasitism rate on those large larvae. Foraging decisions of S. harmandi led to the selection of the most profitable host size for parasitoid development, which showed more offspring gained on large M. alternatus larvae than on small larvae and got higher body weight on those large hosts. This study demonstrates the existence of trade-off occurring during host-parasitoids interactions according to host size related quality.

Foraging behavior of the coccinellid Nephus includens (Coleoptera: Coccinellidae) in response to Aphis gossypii (Hemiptera: Aphididae) with particular emphasis on larval parasitism

This study assessed the effect of parasitism of Nephus includens (Col.: Coccinellidae) larvae by Homalotylus flaminius (Hym.: Encyrtidae) on the predation rates of the predator on the cotton aphid, Aphis gossypii Glover (Hem.: Aphididae) by deriving functional responses for second- and fourth-instar predators at prey densities ranging from 10 to 80 aphids per arena. The relationship between the functional and numerical responses of adult females of N. includens also was determined for prey densities ranging from 10 to 140 aphids per arena. Predation rates of unparasitized and parasitized second-instar N. includens were both fit by a type II functional response model with parameters as follows: unparasitized (a = 0.0768 hours(-1) and T(h) = 0.975 h) and parasitized (a = 0.0787 hours(-1) and T(h) = 0.8823 hours). Predation rates of unparasitized and parasitized fourth-instar N. includens were fit by type III and II models, respectively, with the following parameters: unparasitized (b = 0.1702 hours(-1) and T(h) = 0.2369 hours) and parasitized (a = 0.038 h(-1) and T(h) = 0.539 h). The unparasitized fourth-instar was the most voracious stage, having the highest attack rate and lowest handling time. Considering these attributes, it would seem to be the most effective stage of this predator against A. gossypii. Adult female lady beetles (N. includens) showed a type III functional response and their numerical response increase to prey density was curvilinearly related to prey density, with the highest number of eggs being produced at highest prey densities. The maximum saturation level for both predation and egg production for adult females occurred at a prey density of 120 aphids. Thus, a ratio 1:120 (predator:prey) should be used when releasing this species for augmentative biological control. Release of either fourth-instar or adult stage N. includens should be minimized the potentially negative effect of parasitism by H. flaminius on early developmental stages, and hence increase its efficiency in biocontrol programs.

Association of Ovavesicula popilliae (Microsporida: Ovavesiculidae) with winter mortality of larvae and reduced fecundity of female Japanese beetles (Coleoptera: Scarabaeidae)

Populations of Japanese beetle at sites in Michigan where Ovavesicula popilliae (Andreadis) was introduced in 1999 and 2000 were compared with nearby control sites from fall of 2005 through spring of 2008. Percent infection by O. popilliae and winter mortality of Japanese beetle were determined by sampling larvae in October and April from 12 golf holes on six courses in southeast Michigan and eight holes on four courses in southwest Michigan. Adult Japanese beetles were also collected from these golf courses in July and August of 2007 to determine the impact of O. popilliae-infection on egg development in females. In southeast Michigan, O. popilliae appeared to spread rapidly from the 100 m(2) plots where it was previously introduced to surrounding golf course holes between 2000 and 2006. However, data from southwest Michigan suggests that O. popilliae had already been introduced into the area. Regression analysis of data from all 20 golf course holes gives a significant relationship between percent infection of larvae with O. popilliae and winter mortality of Japanese beetle. Mean winter mortality of larvae around golf course holes where <10% were infected with O. popilliae was 24.7% compared with 41.7% mortality where 10-30% were infected, and 72.0% mortality where >30% were infected. Females infected with O. popilliae contained 50% fewer mature eggs than uninfected females. In addition, females from golf courses where all of the fairways and roughs were treated annually with imidacloprid contained 48% fewer mature eggs than females from golf courses where insecticides were only used on the fairways or not at all.

[The fine structure of the cortical zone in the gregarine Bothriopsides histrio (Eugregarinida: Actinocephalidae)]

Attached and non-attached trophozoites of the septate gregarine Bothriopsides histrio were found in the intestine of the freshwater beetle Acilius sulcatus. Circular folds in the border between proto- and deutomerites and longitudinal striation, running along the entire body of the parasite, were revealed in an optical microscope. Our studies have demonstrated that circular folds, forming a specific collar, are formed of ecto- and endocytes. The longitudinal striation is represented by overdeveloped folds developed by the epicyte and the ectocite. Numerous typical epicite folds were observed over the entire cell surface. Additionally, the symbiosis between gregarine cells and bacteria was revealed.

Host suitability of a gregarious parasitoid on beetle hosts: flexibility between fitness of adult and offspring

Behavioral tactics play a crucial role in the evolution of species and are likely to be found in host-parasitoid interactions where host quality may differ between host developmental stages. We investigated foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi in relation to two distinct host developmental stages: larvae and pupae. Two colonies of parasitoids were reared on larvae of Monochamus alternatus and Saperda populnea (Cerambycidae: Lamiinae). Paired-choice and non-choice experiments were used to evaluate the preference and performance of S. harmandi on larvae and pupae of the two species. Foraging decisions and offspring fitness-related consequences of S. harmandi led to the selection of the most profitable host stage for parasitoid development. Adult females from the two colonies oviposited more quickly on pupae as compared to larvae of M. alternatus. Subsequently, their offspring development time was faster and they gained higher body weight on the pupal hosts. This study demonstrates optimal foraging of intraspecific détente that can occur during host-parasitoid interactions, of which the quality of the parasitism (highest fitness benefit and profitability) is related to the host developmental stage utilized. We conclude that S. harmandi is able to perfectly discriminate among host species or stages in a manner that maximizes its offspring fitness. The results indicated that foraging potential of adults may not be driven by its maternal effects, also induced flexibly with encountering prior host quality.

Effects of rearing conditions on reproduction of Spathius agrili (Hymenoptera: Braconidae), a parasitoid of the emerald ash borer (Coleoptera: Buprestidae)

Spathius agrili Yang (Hymenoptera: Braconidae) can be successfully reared on emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), larvae feeding in chambers drilled in small ash twigs that are wrapped with floral tape. Females maintained in groups with males for one week can receive enough sperm for production of female progeny throughout their lives. Volatiles released by emerald ash borer adults feeding on ash foliage increased parasitoid fecundity over ash foliage alone or no stimulus. The temperature at which the parasitoids were reared ranged from 20 to 25 degrees C in a daily cycle; however, raising the daily maximum temperature to 28 degrees C did not affect parasitoid longevity or fecundity. Adult females lived between 12 and 127 d, with an average of 60.8 +/- 4.5 d. Males lived slightly longer, with an average of 66 +/- 4.5 d. The first clutch of eggs was laid when the female was between 2 and 42 d old, with the average preoviposition period lasting 11.4 +/- 1.4 or 19.5 +/- 2.0 d in 2007 and 2009 trials, respectively. A higher proportion of the emerald ash borer larvae were feeding and thus attractive to parasitoids in the 2009 trial, and female S. agrili laid an average of 9.5 +/- 1.0 clutches containing 5.4 +/- 0.2 eggs, for an average of 51.2 eggs per female. Approximately three quarters of the progeny were female. The number of eggs per clutch was significantly greater when deposited on larger emerald ash borer larvae, further highlighting the need for quality larvae in rearing. Chilling S. agrili pupae at 10 degrees C to stockpile them for summer release was not successful; chilling resulted in lower survival and lower fecundity of emerging progeny. Female S. agrili proved capable of attacking emerald ash borer larvae through even the thickest bark of an ash tree that was 30-cm diameter at breast height. Even emerald ash borer larvae that were creating overwintering chambers in the outer sapwood of the tree were successfully attacked, suggesting that S. agrili could be reared on field collected logs infested with emerald ash borer.

Role of emerald ash borer (Coleoptera: Buprestidae) larval vibrations in host-quality assessment by Tetrastichus planipennisi (Hymenoptera: Eulophidae)

The biological control agent Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) is a gregarious larval endoparasitoid of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive cambium-feeding species responsible for recent, widespread mortality of ash (Fraxinus spp.) in North America. T. planipennisi is known to prefer late-instar emerald ash borer, but the cues used to assess host size by this species and most other parasitoids of concealed hosts remain unknown. We sought to test whether vibrations produced by feeding emerald ash borer vary with larval size and whether there are any correlations between these cues and T. planipennisi progeny number (i.e., brood size) and sex ratio. The amplitudes and rates of 3-30-ms vibrational impulses produced by emerald ash borer larvae of various sizes were measured in the laboratory before presenting the larvae to T. planipennisi. Impulse-rate did not vary with emerald ash borer size, but vibration amplitude was significantly higher for large larvae than for small larvae. T. planipennisi produced a significantly higher proportion of female offspring from large hosts than small hosts and was shown in previous work to produce more offspring overall from large hosts. There were no significant correlations, however, between the T. planipennisi progeny data and the emerald ash borer sound data. Because vibration amplitude varied significantly with host size, however, we are unable to entirely reject the hypothesis that T. planipennisi and possibly other parasitoids of concealed hosts use vibrational cues to assess host quality, particularly given the low explanatory potential of other external cues. Internal chemical cues also may be important.

Parasitism of lepidopterous stem borers in cultivated and natural habitats

Plant infestation, stem borer density, parasitism, and parasitoid abundance were assessed during two years in two host plants, Zea mays (L.) (Cyperales: Poaceae) and Sorghum bicolor (L.) (Cyperales: Poaceae), in cultivated habitats. The four major host plants (Cyperus spp., Panicum spp., Pennisetum spp., and Sorghum spp.) found in natural habitats were also assessed, and both the cultivated and natural habitat species occurred in four agroecological zones in Kenya. Across habitats, plant infestation (23.2%), stem borer density (2.2 per plant), and larval parasitism (15.0%) were highest in maize in cultivated habitats. Pupal parasitism was not higher than 4.7% in both habitats, and did not vary with locality during each season or with host plant between each season. Cotesia sesamiae (Cameron) and C. flavipes Cameron (Hymenoptera: Braconidae) were the key parasitoids in cultivated habitats (both species accounted for 76.4% of parasitized stem borers in cereal crops), but not in natural habitats (the two Cotesia species accounted for 14.5% of parasitized stem borers in wild host plants). No single parasitoid species exerted high parasitism rates on stem borer populations in wild host plants. Low stem borer densities across seasons in natural habitats indicate that cereal stem borer pests do not necessarily survive the non-cropping season feeding actively in wild host plants. Although natural habitats provided refuges for some parasitoid species, stem borer parasitism was generally low in wild host plants. Overall, because parasitoids contribute little in reducing cereal stem borer pest populations in cultivated habitats, there is need to further enhance their effectiveness in the field to regulate these pests.

Biology and life history of Balcha indica, an ectoparasitoid attacking the emerald ash borer, Agrilus planipennis, in North America

Balcha indica Mani and Kaul (Hymenoptera: Eupelmidae) is a solitary ectoparasitoid attacking larvae, prepupae, and pupae of the emerald ash borer, Agrilus planipennis Fairmaire (Hymenoptera: Eupelmidae). Its fecundity, oviposition rate, longevity, and development time were determined in the laboratory under standard rearing conditions (25 ± 2° C, 65 ± 10% relative humidity, and 14:10 L:D). Adults lived a mean of 59 days with a maximum of 117 days. Lifetime adult fecundity averaged 36 eggs with a maximum 94 eggs per female. The egg stage lasted for a maximum of four days with ~ 50% eggs hatched within two days. The development time of the first instars lasted for a maximum of nine days; 50% of the first instars completed their development (i.e., molted to the next instar) within five days. Instars of the intermediate and final stage larvae (after molting of the first instars occurred) could not be distinguished until they reached the pupal stage, and 50% of those larvae pupated ~ 62 days after adult oviposition. Under the standard rearing conditions, 50% of B. indica took ~ 83 days to complete the life cycle (from egg to adult emergence) ranging from 47 to 129 days. These results suggest that B. indica may not have more than two generations in the mid-Atlantic and Midwest regions of United States, where normal growing seasons--with average temperature above 25° C--are normally less than six months (May-October). Because of the long life span and oviposition period of adults, however, B. indica is likely to have overlapping generations.

Field-cage methodology for evaluating climatic suitability for introduced wood-borer parasitoids: preliminary results from the emerald ash borer system

Field-cage methods were developed to evaluate the abilities of Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) and Spathius agrili Yang (Hymenoptera: Braconidae), biocontrol agents of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), to parasitize, develop and overwinter following three late-season releases at both a northern (Michigan) and a southern (Maryland) location within the current North American range of A. planipennis. In August, September and October of 2009, five young green ash trees were selected at each location. Tetrastichus planipennisi and S. agrili were each randomly assigned to one of two cages attached to each tree, surrounding separate sections of trunk in which late-instar A. planipennis had been inserted. The following April, the caged trunk sections were dissected to determine the fate of each A. planipennis larva and the developmental stages of all recovered parasitoid progeny. At both locations, T. planipennisi and S. agrili were able to parasitize hosts and successfully overwinter (i.e., reach adulthood the following spring). For T. planipennisi, successful parasitism (i.e., parasitoid progeny reached adulthood) occurred for all caged releases in Maryland, but only for the August and September releases in Michigan. At both locations, percent parasitism by T. planipennisi was higher in August and September than in October. For S. agrili, successful parasitism occurred for all caged releases in Maryland, but only for the August release in Michigan. In Maryland, percent parasitism by S. agrili in August and September was higher than in October. The caging method described here should be useful in determining the climatic suitability of other regions before proceeding with large-scale releases of either species and may have utility in other wood-borer parasitoid systems as well.

Orientation mechanisms and sensory organs involved in host location in a dipteran parasitoid larva

The robber fly Mallophora ruficauda is one of the principal pests of apiculture in the Pampas region of Argentina. Larvae are solitary ectoparasitoids of third-instar scarab beetle larvae. Females of M. ruficauda do not lay eggs on or near the hosts, but on tall grasses. After hatching, larvae are dispersed by the wind and drop to the ground, where they dig and search for potential hosts. It is known that second-instar larvae of M. ruficauda exhibit active host-searching behaviour towards their preferred hosts, i.e., third-instar larvae of Cyclocephala signaticollis. Although host-location seems to be mediated by chemical cues, the mechanism of orientation and the sensory organs involved in host location remain unknown. We carried out behavioural experiments in the laboratory to address these questions. We also tested whether the orientation behaviour is exclusively based on the use of chemical cues. We found that larvae of M. ruficauda detect the chemicals with chemosensilla on the maxillary palps. Only one maxillary palp suffices for orientation, but their bilateral ablation abolishes orientation. Besides, an hexane extract of the host body was as attractive as a live host. Our results support that M. ruficauda larvae find their hosts underground by means of chemoklinotaxis.

Life history of Sancassania polyphyllae (Acari: Acaridae) feeding on dissected tissues of its phoretic host, Polyphylla fullo (Coleoptera: Scarabaeidae): temperature effects

The effect of temperature on the development and fecundity of Sancassania polyphyllae fed on tissues of Polyphylla fullo larvae was studied at 15, 20, 25, 30, and 35 ± 1°C and 65 ± 10% RH in a dark incubator. Mean developmental period of immature stages decreased significantly with increasing temperatures from 15 to 30°C. Developmental periods at 30-35°C were not significantly different. The estimated lower developmental thresholds of the various immature stages ranged between 10.1 and 11.5°C. The thermal constant for the egg-to-female adult was 93.5 degree-days. The pre-oviposition, oviposition, and post-oviposition periods and female longevity were significantly longer at 15°C than at higher temperatures. Mean total and daily fecundity were the highest at 25°C, which were significantly different from those obtained at 15, 20 and 30°C. The net reproductive rate (R (0)) was the highest at 25°C (588.3 ♀/♀). The longest mean generation time (T (0)) occurred at 15°C (36 days) and the shortest occurred at 30°C (9.2 days). The highest intrinsic rate of increase (r (m)) for S. polyphyllae was observed at 25 (0.61 ♀/♀/day) and 30°C (0.62 ♀/♀/day).

Hemocyte responses of the Colorado potato beetle, Leptinotarsa decemlineata, and the greater wax moth, Galleria mellonella, to the entomopathogenic nematodes, Steinernema feltiae and Heterorhabditis bacteriophora

Hemocyte encapsulation reactions of infective juveniles of two Iranian isolates of the entomopathogenic nematodes, Heterorhabditis bacteriophora Poinar (Rhabditina: Heterorhabditidae) and Steinernema feltiae Filipjev (Tylenchina: Steinernematidae), were compared in the economic pest Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), and the greater wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae). The former was a more responsive host than the latter and the hemocyte responses occurred sooner and more extensively. Complete encapsulation of some of the nematodes occurred by 4 h post injection for H. bacteriophora in both L. decemlineata and G. mellonella, and by 2 h pi for S. feltiae in L. decemlineata. The percentage of encapsulation from 24 h to 72 h pi in L. decemlineata was 86.2% for S. feltiae and 39% for H. bacteriophora. In G. mellonella there were no encapsulation or melanization responses against S. feltiae, whereas when H. bacteriophora was encapsulated and melanized (16.7%) the encapsulation level was lower than in L. decemlineata. This study may contribute to effectively selecting entomopathogenic nematode species active against significant economic pests based on the latter's cellular immune response.

Incidence of turf-damaging white grubs (Coleoptera: Scarabaeidae) and associated pathogens and parasitoids on Kentucky golf courses

Root-feeding grubs (Coleoptera: Scarabaeidae) were sampled from damaged areas of 61 irrigated roughs on 32 Kentucky golf courses to determine species composition and natural enemy incidence, the first such survey in the United States' transitional turfgrass climatic zone. Masked chafers (Cyclocephala lurida Bland and C. borealis Arrow) and Japanese beetle (Popillia japonica Newman) accounted for ≈73 and 26% of grubs found in an autumn survey, with Cyclocephala spp. predominating at most sites, although mixed infestations were common. Only a few Phyllophaga spp., and no exotic species other than P. japonica were found. Cyclocephala spp. also predominated in seasonal and statewide surveys regardless of whether a course had cool- or warm-season grass fairways. Pathogenic bacteria, Paenibacillus and Serratia spp., and the autumn-active parasitoid Tiphia pygidialis Allen were the main enemies associated with Cyclocephala spp. Predominant enemies of P. japonica were Paenibacillus, Serratia, and Metarhizium spp. in autumn, and eugregarines, Stictospora sp. (probably S. villani Hays and Clopton) and Tiphia vernalis Rohwer in spring. Entomopathogenic nematodes and the microsporidian Ovavesicula popilliae Andreadis & Hanula were nearly absent in our samples. No predictive relationships were found between soil parameters and proportionate abundance of Cyclocephala or P. japonica, or with natural enemy incidence at particular sites. Although incidence of individual enemies was generally low (<20%; often <5%) in these point-in-time surveys, collectively and over their hosts' prolonged development they may take a significant toll on grub populations.

Host species critical for offspring fitness and sex ratio for an oligophagous parasitoid: implications for host coexistence

In theory, inferior apparent competitors sharing a natural enemy with superior apparent competitors should be excluded in the absence of stabilising factors. Nevertheless, plentiful examples of coexisting apparent competitors exist. In this paper, we show that parasitoid resource competition within hosts affects both parasitoid sex ratio and female body size, with implication for population growth and apparent competition between the two closely related hosts experiencing a strong asymmetry in their interaction. While the superior competitor delivers parasitoids with higher fitness to the shared parasitoid pool, the inferior competitor delivers a higher proportion of female parasitoids. Hence, the inferior host experience an inflow of fit parasitoids from the superior competitor, which should increase the risk of exclusion, but also an outflow of parasitoid females, which should reduce the risk of exclusion and increase stability. We conclude that differential outcomes of parasitoid resource competition in different host species may have profound effects on shared parasitoid populations and should be included in future studies of apparent competition between hosts.

Measuring the impact of biotic factors on populations of immature emerald ash borers (Coleoptera: Buprestidae)

Cohorts of emerald ash borer larvae, Agrilus planipennis Fairmaire, were experimentally established in July of 2008 on healthy green ash (Fraxinus pennsylvanica) trees in two wooded plots at each of three sites near Lansing, MI, by caging gravid emerald ash borer females or placing laboratory-reared eggs on trunks (0.5-2 m above the ground) of selected trees. One plot at each site was randomly chosen for release of two introduced larval parasitoids, Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) and Spathius agrili Yang (Hymenoptera: Braconidae), whereas the other served as the control. Stage-specific mortality factors and rates were measured for all experimentally established cohorts and for associated wild (i.e., naturally occurring) emerald ash borer immature stages via destructive sampling of 2.5 m (above the ground) trunk sections of cohort-bearing trees in the spring and fall of 2009. Host tree defense was the most important mortality factor, causing 32.0 to 41.1% mortality in the experimental cohorts and 17.5 to 21.5% in wild emerald ash borer stages by spring 2009, and 16.1 to 29% for the remaining experimental cohorts, and 9.9 to 11.8% for wild immature emerald ash borer stages by fall 2009. Woodpecker predation was the second most important factor, inflicting no mortality in the experimental cohorts but causing 5.0 to 5.6% mortality to associated wild emerald ash borer stages by spring 2009 and 9.2 to 12.8% and 3.2 to 17.7%, respectively, for experimental cohorts and wild emerald ash borer stages by fall 2009. Mortality from disease in both the experimental and wild cohorts was low (<3%) in both the spring and fall sample periods. In the fall 2009 samples, ≈ 1.5% of experimental cohorts and 0.8% of the wild emerald ash borer stages were parasitized by T. planipennisi. While there were no significant differences in mortality rates because of parasitism between parasitoid-release and control plots, T. planipennisi was detected in each of the three release sites by the end of the study but was not detected in the experimental cohorts or associated wild larvae in any of the three control plots.

[Carcinops troglodytes (Erichson) (Coleoptera: Histeridae) preying on Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) in poultry houses]

We first record Carcinops troglodytes (Paykull) as a predator of Alphitobius diaperinus (Panzer) larvae in poultry houses in North and Northwest regions of the state of Paraná. Carcinops spp. are commonly recorded as predators of dipterans, and this record in poultry houses indicates the possibility of exploiting such predator for future studies aiming the development of management strategies for A. diaperinus.

Suitability and accessibility of immature Agrilus planipennis (Coleoptera: Buprestidae) stages to Tetrastichus planipennisi (Hymenoptera: Eulophidae)

Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), a gregarious larval endo-parasitoid, is one of three biocontrol agents from Asia currently being released in the United States to combat the invasive emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). The current protocol for rearing T. planipennisi involves presenting the wasps with artificially infested ash sticks made by placing field-collected larvae into shallow grooves beneath flaps of bark. Although third and fourth instars are readily accepted by T. planipennisi in these exposures, the suitability of younger or older developmental stages, which are often more readily available in the field, has not been tested. In this study, we used both artificially infested ash sticks and naturally infested ash logs to test which emerald ash borer developmental stages (second to fourth instars, J larvae [preprepupae], prepupae, and pupae) are most suitable for rearing T. planipennisi. T. planipennisi parasitized all stages except for pupae, but parasitized fewer J larvae and prepupae in naturally infested logs than in artificially infested ash sticks. This is probably because, in naturally infested ash logs, these stages were confined to pupal chambers excavated in the sapwood and may have been largely beyond the reach of ovipositing T. planipennisi. The number of T. planipennisi progeny produced was positively correlated (logarithmic) with host weight, but this relationship was stronger when J larvae and prepupae were excluded from the data set. Fourth instars yielded the most parasitoid progeny, followed by, in approximately equal numbers, J larvae, prepupae, and third instars. Second instars yielded too few parasitoid progeny to benefit rearing efforts.

Mortality of four stored product pests in stored wheat when exposed to doses of three entomopathogenic nematodes

The insecticidal effect of Heterorhabditis bacteriophora Poinar (Nematoda: Heterorhabditidae), Steinernema carpocapsae (Weiser) (Nematoda: Steinernematidae), and Steinernema feltiae (Filipjev) (Nematoda: Steinernematidae) against Mediterranean flour moth, Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) (larvae), lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) (adults), rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) (adults), and confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) (adults and larvae) was examined under laboratory conditions in wheat, Triticum aestivum L. The nematodes were applied at the following doses: 0 (control), 100, 500, 1,000, 1,500, 5,000, 10,000, and 20,000 infective juveniles (IJs) per ml, corresponding to 10, 50, 100, 150, 500, 1,000, and 2,000 IJs per insect, and their infectivity was tested at 20 and 30 degrees C after 4 and 8 d of exposure. For E. kuehniella larvae wheat treatments with S. feltiae provided mortality that ranged from 36.7 to 78.3% whereas no mortality was noted in the treatment with S. carpocapsae at 100 IJs per ml at 20 or at 30 degrees C. Also, at 20 degrees C, in wheat treated with H. bacteriophora at 100 IJs per ml, very few larvae were dead. For R. dominica adults, at 20 degrees C, the mortality of adults in wheat treated with S. feltiae and S. carpocapsae did not exceed 23.3 and 41.7%, respectively, at 20,000 IJs per ml, with no significant differences among doses. In the case of S. oryzae adults, the mortality was very low at all doses, and temperatures and did not exceed 9%. Mortality of T. confusum adults did not exceed 17% regardless of the entomopathogenic nematode species tested. In contrast, mortality of T. confusum larvae was notably higher and exceeded 56% in wheat treated with 10,000 or 20,000 IJs per ml of S. feltiae at 20 degrees C. Unlike S. feltiae and S. carpocapsae, the application of H. bacteriophora resulted in lower mortality levels. Generally, the increase of temperature reduced the mortality levels of the T. confusum larvae. In most cases, the efficacy level of the tested entomopathogenic nematode species increased with the dose and decreased with the increase of temperature.