The brown marmorated stink bug, Halyomorpha halys (Stål), is native to eastern Asia and is presently invading North America. Little is known about the exposure to and effects of winter temperatures in newly invaded regions on H. halys. The overwintering habitats that this species utilizes vary greatly in their thermal buffering capacity. They naturally overwinter in aggregations beneath loose bark on trees and in cliff outcroppings, but will also commonly aggregate in buildings. Effects of cold temperatures such as mortality and freezing have yet to be quantified in the invading population. We report that H. halys is chill intolerant (i.e., dies before reaching its freezing point), and that the degree of cold tolerance of populations in North America differs by season, sex, and acclimation location. The mean winter supercooling point (± SEM) of individuals acclimated in Minnesota was −17.06°C ± 0.13 and in Virginia was −13.90°C ± 0.09. By using laboratory assays of lower lethal temperatures and ambient air temperature records, we accurately forecasted mortality for field experiments in Minnesota and Virginia. Temperature refugia provided by human-built structures are likely crucial for overwintering survival during atypically cold winters and possibly contribute to the northern geographic range expansion of this economically damaging insect in the temperate climates of North America.

Cockroaches are a group of insects that evolved early in geological time. Because of their antiquity, they for the most part display generalized behavior and physiology and accordingly have frequently been used as model insects to examine physiological and biochemical mechanisms involved with water balance, nutrition, reproduction, genetics, and insecticide resistance. As a result, a considerable amount of information on these topics is available. However, there is much more to be learned by employing new protocols, microchemical analytical techniques, and molecular biology tools to explore many unanswered questions.

Exposure of adult mosquitoes to pyriproxyfen (PPF), an analog of insect juvenile hormone (JH), has shown promise to effectively sterilize female mosquitoes. However, the underlying mechanisms of the PPF-induced decrease in mosquito fecundity are largely unknown. We performed a comprehensive study to dissect the mode of PPF action in Aedes aegypti mosquitoes. Exposure to PPF prompted the overgrowth of primary follicles in sugar-fed Ae. aegypti females but blocked the development of primary follicles at Christopher’s Stage III after blood feeding. Secondary follicles were precociously activated in PPF-treated mosquitoes. Moreover, PPF substantially altered the expression of many genes that are essential for mosquito physiology and oocyte development in the fat body and ovary. In particular, many metabolic genes were differentially expressed in response to PPF treatment, thereby affecting the mobilization and utilization of energy reserves. Furthermore, PPF treatment on the previtellogenic female adults considerably modified mosquito responses to JH and 20-hydroxyecdysone (20E), two major hormones that govern mosquito reproduction. Krüppel homolog 1, a JH-inducible transcriptional regulator, showed consistently elevated expression after PPF exposure. Conversely, PPF upregulated the expression of several key players of the 20E regulatory cascades, including HR3 and E75A, in the previtellogenic stage. After blood-feeding, the expression of these 20E response genes was significantly weaker in PPF-treated mosquitoes than the solvent-treated control groups. RNAi-mediated knockdown of the Methoprene-tolerant (Met) protein, the JH receptor, partially rescued the impaired follicular development after PPF exposure and substantially increased the hatching of the eggs produced by PPF-treated female mosquitoes. Thus, the results suggested that PPF relied on Met to exert its sterilizing effects on female mosquitoes. In summary, this study finds that PPF exposure disturbs normal hormonal responses and metabolism in Ae. aegypti, shedding light on the molecular targets and the downstream signaling pathways activated by PPF. Aedes aegypti mosquitoes are responsible for the transmission of dengue, yellow fever, chikungunya, and Zika fever. Insecticides are widely used as the primary tool in the prevention and control of these infectious diseases. In light of the rapid increase of insecticide resistance in mosquito populations, there is an urgent need to find new classes of insecticides with a different mode of action. Here we found that pyriproxyfen, an analog of insect juvenile hormone (JH), had a large impact on the oocyte development, both before and after blood feeding, in female mosquitoes. Pyriproxyfen disturbed normal hormonal responses and caused metabolic shifting in female adults. These actions appear to collectively impair oocyte development and substantially reduce viable progenies of female mosquitoes. Besides, we demonstrated the involvement of the JH receptor Met in pyriproxyfen-induced female sterilization. This study significantly advances our understanding of mosquito reproductive biology and the molecular basis of pyriproxyfen action, which are invaluable for the development of new mosquito control strategies.

SUMMARY: Female German cockroaches usually carry their oothecae until they hatch. The success of embryogenesis may be dependent on the water-balance relationship between females and their developing oothecae. Oothecae detached from females early in embryogenesis often fail to develop, especially in low-humidity environments. Experiments reported here using tritiated water have confirmed the transport of a significant amount of water to the ootheca from the female during embryogenesis; 18% of the tritiated water injected into gravid females was recovered in their oothecae after 24 h. We describe a structural basis of water absorption by the oothecae. An area located on the proximal end of the ootheca (adjacent to the `escutcheon-shaped vaginal imprint') contains small pores that penetrate the oothecal covering to access regions of the chorion lying beneath these pores. Experiments using microparabiotic chambers to examine transport of tritiated water and water-soluble materials across the escutcheon region of the oothecal covering, along with dark-field birefringent microscopy of the chorion, support the hypothesis that this chorionic network is capable of conducting water throughout the interior of the ootheca. Furthermore, the structural arrangement and intimate association of the female vestibulum with the oothecal pore field contained in the region of the escutcheon-shaped vaginal imprint appear to provide an efficient conduit to the chorion. The overall structural relationship might be a means for maintaining water balance between females and their oothecae during embryonic development. Evidence presented here supports observations that this species represents an important link in the transition from oviparity to ovoviviparity by internalization of cockroach oothecae.

The harlequin bug, Murgantia histrionica (Hahn), is a serious pest of brassicaceous vegetables in southern North America. While this insect is limited in its northern range of North America, presumably by severe cold winter temperatures, specific information on its cold hardiness remains unknown. We determined the supercooling points (SCPs) for Maryland and Virginia adult populations and found no significant difference among these populations. SCPs were similar for adults (X- = −10.35 °C; σX= 2.54) and early and late instar (X- = −11.00 °C; σX= 4.92) and between adult males and females. However, SCPs for first instars (X- = −21.56 °C; σX=1.47) and eggs (X- = −23.24 °C; σX=1.00) were significantly lower. We also evaluated field survival of overwintering harlequin bug adults during extreme cold episodes of January 2014 and January 2015, which produced widespread air temperatures lower than −15 °C and subfreezing soil temperatures in the Mid-Atlantic Region. After the 48-h episode in 2014, bug mortality in exposed field sites averaged 88%, compared to <5% mortality of bugs sheltered in an unheated greenhouse (recorded minimum temperature 4.4 °C). After the 2015 episode, ∼80% of adults that were established in the field the previous November and then sheltered in an unheated garage during the episode, died, in contrast to 96% mortality in exposed field sites. Our results provide new information on M. histrionica overwintering biology, and thermal limitations to its distribution, which leads to improved predictive capabilities to forecast pest severity.

The behavior and daily activity patterns of two specialist predators, Laricobius nigrinus Fender (Coleoptera: Derodontidae) and Sasajiscymnus tsugae,