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The chestnut gall wasp (CGW), Dryocosmus kuriphilusYasumatsu, 1951 (Cynipini, Cynipoidea, Hymenoptera), is a globally invasive pest on chestnuts (Castanea spp., Fagaceae). Since its first reported occurrence in the state of Georgia in 1974, CGW has been reported to have spread to 16 additional states in the eastern United States. Despite its wide occurrence, investigations of the invasion and colonization history of CGW have not been conducted. To address this shortcoming, we screened one mitochondrial (cytochrome c oxidase subunit 1; COI) and one nuclear gene (internal transcribed spacer 2; ITS2) to examine the genetic variation across four discrete CGW populations from four states (New Jersey, Pennsylvania, Maryland, Tennessee). We tested whether CGW in the eastern U.S. originated from one or multiple introductions followed by subsequent dispersal. Additional insights came from comparing the sequences with two CGW populations sampled from its native range in mainland China, and one population each from Taiwan and Japan. Sequences revealed that both genes exhibit the same haplotype across all sampled specimens of all locations. The COI haplotype in this study is the dominant haplotype recorded in China, while the haplotype of ITS2 has been reported in both Japan and Europe. The uniformity of genetic structure suggests that CGW invasion in the U.S. could have either single or multiple origins, or both, accompanied with the common haplotype on each occasion. Further insights into the invasion history and expansion of CGW in the U.S. will require a combination of sampling more populations and utilizing a next generation sequencing strategy. [ABSTRACT FROM AUTHOR]

Environmental stressors may induce variation in the number of larval instars of holometabolous insects. Host plant quality and ambient temperature can both induce this life history shift in the silver-spotted skipper, Epargyreus clarus (Cramer 1775) (Lepidoptera: Hesperiidae). To better understand this phenomenon, we raised larvae on high-quality (kudzu) or low-quality (wisteria) host plants in growth chambers under three temperature regimes (20, 26, and 32°C) that were either constant or diurnally fluctuating (T ± 5°C), and recorded survival and incidence of supernumerary instars. Larvae feeding on the low-quality host and/or experiencing thermal stress were more likely to show supernumerary development (SD). A subset of treatments yielded a mix of SD and TD (typical development) individuals, allowing for comparisons between phenotypes. Under the most stressful treatment (20 ± 5°C, wisteria), development time was 9 days longer in SD than in TD individuals; by contrast, at typical summer temperatures (26 ± 5°C), also on wisteria, total development time did not differ between these two phenotypes. Head capsules of both second and third instars were smaller in SD individuals. A retrospective logistic regression analysis indicated that third-instar head capsule size could be used to predict expression of the SD phenotype. By the ultimate instar, however, there were no detectable differences in head capsule size, and SD and TD individuals did not differ in pupal mass, strongly suggesting that the SD phenotype functions as a compensatory mechanism allowing E. clarus larvae to achieve the same size at metamorphosis (a strong fitness correlate) as TD larvae. [ABSTRACT FROM AUTHOR]

1. Eastern tent caterpillars (Malacosoma americanum) are broadly distributed within North America, with populations spanning a wide range of environmental conditions. Their egg masses are consistently attacked by a variety of wasps in the superfamily Chalcidoidea. We performed a reciprocal transplant‐type experiment to assess the performance of three populations spanning 15° of latitude when subjected to temperature regimes resembling southern or northern conditions. 2. Exposure to warm temperatures and short overwintering periods (southern conditions) resulted in the increased survival of both caterpillars and parasitoids from all populations. By contrast, the ability of caterpillars to withstand starvation was maximised when exposed to conditions similar to their native region. 3. Caterpillar and wasp phenology differed among populations even when exposed to the same temperature regime. Individuals exposed to novel conditions hatched 2–6 weeks later than those experiencing native conditions. Under typical conditions, the relative phenology of wasps and their hosts exhibited a latitudinal gradient consistent with growing season length, with southern, central, and northern wasps, emerging 50, 45, and 36 days, respectively, after their hosts. 3. We identified four genera of primary parasitoids, which emerged within a narrow 2‐week span, and one hyperparasitoid, which emerged in distinct pulses over an approximately 5‐week span, possibly indicating the presence of a second generation. 4. Caterpillars and wasps exhibited distinct phenological responses according to population of origin, indicating that not only pre‐hatching winter and spring conditions, but also historical factors, which may include local adaptation, maternal effects, and oviposition time, influence their phenological responses. The period between eastern tent caterpillars hatching and the emergence of their egg parasitoids exhibited a latitudinal gradient consistent with growing season length.We identified four genera of primary parasitoids, which emerged within a narrow 2‐week span, and one hyperparasitoid, which emerged in distinct pulses over an approximately 5‐week span.Caterpillars and wasps exhibited distinct phenological responses according to population of origin, indicating that not only pre‐hatching winter and spring conditions, but also historical factors influence their phenological responses. [ABSTRACT FROM AUTHOR]