Light traps are a useful method for monitoring and controlling the important migratory pest, the fall armyworm, Spodoptera frugiperda. Studies have shown that S. frugiperda is sensitive to blue, green, or ultraviolet (UV) light, but the conclusions are inconsistent. Furthermore, conventional black light traps are less effective for trapping S. frugiperda. To improve the trapping efficiency of this pest, it is crucial to determine the specific wavelength to which S. frugiperda is sensitive and measure its flight capability under that wavelength. This study investigated the effects of light wavelength on the phototaxis and flight performance of S. frugiperda. The results showed that blue light was the most sensitive wavelength among the three different LED lights and was unaffected by gender. The flight capability of S. frugiperda varied significantly in different light conditions, especially for flight speed. The fastest flight speed was observed in blue light, whereas the slowest was observed in UV light compared to dark conditions. During a 12 h flight period, speed declined more rapidly in blue light and more slowly in UV, whereas speed remained stable in dark conditions. Meanwhile, the proportion of fast-flying individuals was highest under blue light, which was significantly higher than under UV light. Therefore, the use of light traps equipped with blue LED lights can improve the trapping efficiency of S. frugiperda. These results also provide insights for further research on the effects of light pollution on migratory insects.

In the scenario that requires the biological control of pests using predatory enemies, predators not only prey on pests directly but also can affect the population fitness of pests through indirect non-consumptive effects (predation risk effects). However, the impact of predation risk effects varies depending on the mode of stress imposed by natural enemies and the state of the stressed pests. Herein, we exposed aphids (Periphyllus koelreuteriae) at different stages to various cues from the multicolored Asian lady beetle (Harmonia axyridis) to assess the effects of different predation risks on P. koelreuteriae development and reproduction. We found that the effect of predation risk on aphid developmental time was clearly stage-dependent. When 1st-instar nymphs were exposed to predator cues, their developmental time was prolonged only in the early stages (1st–3rd instar nymphs). Similarly, when third-instar nymphs were stressed, only the current stage (third instar) showed a developmental delay, while fourth-instar nymphs and adult aphids were not significantly affected. Additionally, aphids at different stages perceive predation risk differently. Nymphs cannot recognize visual cues from predators, but can perceive odor cues. In contrast, adult aphids are sensitive to a variety of predator cues, including visual ones. Predation risk caused aphids to shorten their adult lifespan and reduce reproductive output, but it increased the proportion of diapause offspring. This study highlights the importance of considering how predation risk affects multiple life stages and physiological changes, which are important for gaining insights into the mechanisms of predator–prey interactions and for comprehensively assessing the ability of lady beetles to regulate aphid populations.

Histia rhodope (Cramer) (Lepidoptera: Zygaenidae) is an important pest that damages the landscape of Bischofia polycarpa (Levl.) trees. Its larval feeding on the leaves impairs tree growth and urban landscapes, causing significant impacts on local economic and ecological benefits. The insect often overwinters as a cocoon of mature larvae in places such as leaf litter, brick crevices, and tree bark. The low temperatures in winter directly affect the distribution of insect populations, so it is important to explore the molecular mechanisms of overwintering in H. rhodope. RNA-seq technology was used to obtain transcriptome data from 5 different overwintering stages of H. rhodope, and 30 genes related to cold tolerance were screened from the annotation information of differentially expressed gene database (DEGs). Two modules (blue and green) were found to be associated with overwintering by weighted gene co-expression network analysis (WGCNA), identifying translocon-associated protein, thioredoxin, glycine cleavage system H protein, ribosomal proteins, and ATP synthase genes as hub genes. In addition, cytochrome P450 genes were screened. Protein-protein interaction (PPI) network analysis showed that 60 S and 40s ribosomal proteins, putative serine/threonine protein kinase, and heat shock protein 90 had the highest number of direct interactions with other proteins. They might help the larvae successfully overwinter. Ten selected genes were subjected to qRT-PCR to verify the reliability of RNA-seq results. In this study, we obtained transcriptomic data from five different overwintering stages of H. rhodope, revealing key genes associated with this process. This provides a theoretical basis for further research on the molecular mechanisms of overwintering in H. rhodope.

In biological control of pests using predatory natural enemies, predators not only prey on pests directly but also can affect the population fitness of pests through indirect non-consumptive effects (predation risk effects). However, the impact of predation risk effects varies depending on the mode of stress imposed by natural enemies and the state of the stressed pests. Herein, we exposed aphids (Periphyllus koelreuteriae) at different stages to various cues from the multicolored Asian lady beetle (Harmonia axyridis) to assess the effects of different predation risks on P. koelreuteriae development and reproduction. We found that the effect of predation risk on aphid developmental time was clearly stage-dependent. When 1st instar nymphs were exposed to predator cues, their developmental time was prolonged only in the early stages (1st-3rd instar). Similarly, when 3rd instar nymphs were stressed, only the current stage (3rd instar) showed a developmental delay, while 4th instar nymphs and adult aphids were not significantly affected. Additionally, aphids at different stages perceive predation risk differently. Nymphs cannot recognize visual cues from predators but can perceive odor cues. In contrast, adult aphids are sensitive to a variety of predator cues, including visual ones. Predation risk caused aphids to shorten their adult lifespan and reduced reproductive output, but it increased the proportion of diapause offspring. This study highlights the importance of considering how predation risk affects multiple life stages and physiological changes, which are important for gaining insights into the mechanisms of predator-prey interactions and for comprehensively assessing the ability of lady beetles to regulate aphid populations.

The hawthorn spider mite, Amphitetranychus viennensis, can damage various Rosaceae fruit trees. When using predatory natural enemies for biological control, the effects of the physical characteristics of host plant leaves (such as trichomes) on the functional response of predatory natural enemies remain unclear. We studied the functional response of the predatory thrips, Scolothrips takahashii, to feeding on hawthorn spider mite eggs on five host plants (three apple cultivars: Golden Delicious, Fuji, and New Jonagold; peach; and plum). The results revealed that S. takahashii exhibited a typical type II functional response when feeding on mite eggs on Golden Delicious, peach, and plum, which had low trichome density. In contrast, it shifted to a type III functional response when feeding on mite eggs on the two apple cultivars, New Jonagold and Fuji, which had high trichome density. Additionally, the handling time of thrips in the type III response group was significantly longer than that in the type II response group, and the egg consumption at all prey densities was significantly lower than that in the type II response group. This study indicates that the shift in functional response of S. takahashii from type II to type III was associated with an increase in the density of trichomes on the host plant’s leaves, significantly reducing its predation efficiency. This finding reveals the mechanism by which plant physical traits indirectly regulate the predation strategies of natural enemies by influencing predation behavior, providing an important theoretical basis for evaluating the pest control potential of natural enemies and formulating variety layout in orchard habitats based on functional responses.