Abstract Insects have an effective innate immune system that includes both cellular and humoral responses for defense against pathogens. Antimicrobial peptides like gallerimycin and galiomycin, as well as immune proteins like hemolin, are the important effectors of the humoral immune response in Galleria mellonella L. (Lepidoptera:Pyralidae). Encapsulation, on the contrary, is one of the important cellular immune responses. This study investigated the tissue‐specific expression of an immune effector in G. mellonella larvae after injection with Candida albicans (C.P. Robin) (Ascomycota: Debaryomycetaceae) and silica beads. The gene expression of gallerimycin, galiomycin, and hemolin was examined in total larvae, hemocytes, and fat bodies at 4 and 24 h following injection. Our findings indicate that hemocytes serve as the main site for AMP synthesis, especially after bead injection, implying a more effective immune recognition mechanism relative to pathogen injection. Furthermore, we detected higher hemolin expression in hemocytes than fat tissue, indicating its role in hemocyte‐mediated immune responses. Encapsulation rates were also evaluated in bead‐injected larvae. At 4 h post‐injection, most beads were weakly encapsulated, whereas by 24 h, the majority were strongly encapsulated, reflecting a time‐dependent maturation of the immune response. These results show that G. mellonella has a unique immune system, with hemocytes playing a key role in regulating AMP production and immune responses during infection. This study provides deeper insights into the molecular and cellular mechanisms of insect immunity, positioning G. mellonella as a valuable model for studying host–pathogen interactions.

Abstract The Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is one of the most relevant pests in potato cultivation. Even in organic potatoes, CPB are often managed using organically certified insecticides that may also affect non‐target organisms and increase the risk of insecticide resistance. Applying transferred organic mulch to potatoes has been shown to reduce egg masses and larvae of CPB; however, the underlying mechanisms remain unclear. To assess the effects of mulch on the initial infestation of CPB, marked individuals were released in the field between plots with transferred organic mulch and plots with bare soil and counted after 12 h in 2021 and 2022. In 2022, one additional assessment was carried out 72 h after release and eggs and larvae were assessed after 10 days. More than 75% of CPB adults preferred the unmulched plots, a major reason for the reduction of eggs and larvae in mulched potatoes found in previous field trials. Barrier effects, olfactory disruption, or disorientation could be responsible for the reduction.

Abstract To date, the ontogeny of insect sexual size dimorphism (SSD) remains poorly understood. In particular, we do not know whether size differences between sexes might change with rearing temperature. Based on a thorough understanding of the life‐history traits of the fall armyworm (FAW) Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), here, we investigated the ontogeny of SSD by measuring larval mass daily during development at 22 and 28°C. We found that temperature significantly influenced SSD ontogeny. Thus, the growth trajectory at 22°C showed that SSD began between the third instar of larval development and the pupal stage but was not manifest at 28°C. The significant difference in larval mass between sexes reared at 22°C was due to the longer duration of the developmental time of males, whereas the disappearance of SSD at 28°C was mainly attributed to both the longer developmental time of female larvae and the higher growth rate of males. Sexual dimorphism in growth rate was observed at both temperatures, being significantly higher in females than in males at 22°C, over the first 6 days before pupation. Conversely, it was significantly higher in males than in females over the first 5 days before pupation, at 28°C. Unlike female‐biased insects, FAW individuals showed a decrease in SSD from the pupal to adult stages, as male pupae took significantly longer to develop than female pupae, resulting in males losing more weight than females at the time of eclosion. Consequently, females were larger than males at the adult stage. Furthermore, we found a significant positive correlation between larval developmental time and larval mass, as well as between larval mass and wingspan. These findings pave the way for further research on insect SSD.

Abstract Parasitoids, as effective biological control agents, have been extensively applied to reduce the population size of pest species. However, important limitations of biological control programmes are often related to difficulties in synchronizing parasitoid and host life cycles and failure to obtain sufficient numbers of parasitoids when they are required for release. To address these issues, cold storage for parasitized hosts is considered a valuable method. Anastatus disparis Ruschka (Hymenoptera: Eupelmidae) is an important egg parasitoid and is considered a potential biological control agent for several species of lepidopteran forest pests, including Lymantria dispar Linnaeus (Lepidoptera: Lymantriidae). Thus, to synchronize parasitoid and pest host life cycles and obtain an abundance of parasitoids before release, the strategy of cold storage of the parasitized host was studied for A. disparis. Our results suggest immediate refrigeration of the host after parasitization is severely detrimental to the development of the parasitoid A. disparis. More than half of the A. disparis offspring failed to successfully eclose even after a short period of refrigeration, and none eclosed after 60 days. However, when immature A. disparis offspring developed in the host for a period, reaching the larval stage and pupal stage, and were then refrigerated, the eclosion ratio could be significantly improved after long‐term refrigeration. In addition, the sex ratio of the offspring was also evaluated and did not change, although the body size of the offspring decreased in the parasitized host after refrigeration. In summary, our study explored an effective strategy for parasitoid preservation under long‐term cold storage.

Abstract Rising global temperatures can affect host plants and insects in a variety of ways. Species interactions can be disrupted as temperatures increase, particularly when members of different trophic levels show differential responses to thermal stress. In agricultural systems, parasitoids are frequently used as biological control agents to reduce crop damage by herbivores, so understanding the effects of thermal stress on multiple trophic levels is imperative for effective management. We experimentally tested the effects of increased temperatures (ambient: 23–30°C; hot: 27–34°C) on the multi‐trophic interaction involving three varieties of cultivated Brassica oleracea (L.) (Brassicaceae) (cabbage, kale, or broccoli), the caterpillar pest Plutella xylostella (L.) (Lepidoptera: Plutellidae), and its primary parasitoid Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae). We found that performance metrics of both the caterpillar and parasitoid were consistent among host plants. We found decreased development time and reduced pupal weights at higher temperatures in both the caterpillar and the parasitoid, but no effect of temperature on mortality of either the herbivore or its parasitoid. Development time was more accelerated in the caterpillar than the parasitoid, and pupal weights declined more in parasitoids than caterpillars. Caterpillars behaviorally mitigated temperature stress by pupating beneath leaves, resulting in sublethal effects for both hosts and parasitoids. Kale plants growing under higher temperatures had higher foliar nitrogen, but caterpillar performance data suggested that this was due to increased chemical defenses rather than increased nutrition. Together, these results suggest that biological control of P. xylostella could be disrupted by climate change, especially as lower pupal weights are correlated with reduced fecundity, which could reduce parasitoid population densities; however, as the effects of increased temperature are largely consistent across host plants, similar management practices can be used on different host plants.

Abstract Delia platura (Meigen) (Diptera: Anthomyiidae) is a generalist dipteran pest that attacks germinating seeds of cucurbits, crucifers, legumes, and among others. Delia platura can cause economically important damage in early spring that leads to stand losses in temperate regions. Thus, researching the biology and behavior of this pest and running bioassays with different life stages is essential to developing effective management strategies. Maintaining D. platura colonies allows for laboratory and field experiments to occur outside of the growing season. However, current rearing protocols yield high mortality rates at the egg stage and have been difficult to replicate. Here, we present an updated protocol for reduced offspring mortality, improved colony health, and greater ease of maintenance.

Abstract A significant emphasis of insect symbiont research has focused on the digestive tract and elucidating whether bacteria colonize and proliferate or transiently pass through is integral to our understanding of microbial community structure and host–microbe interactions. The larval stages of the greater wax moth, Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae), have become increasingly used in studies that are heavily influenced by host–microbiome dynamics (e.g., plastic biodegradation and innate immunity). However, it is presently unclear whether continual bacterial recruitment is required to sustain the bacterial assemblages, and the extent by which gut bacterial flora is a reflection of their food substrate. Therefore, the objective of this study was to discern between transient and more persistent gut microbes harbored by G. mellonella larvae, and to evaluate their relative contributions to microbial diversity and abundance. We used 16S rRNA sequencing to characterize and compare the bacteriomes of G. mellonella to their natural honeycomb diet throughout larval development, as well as to caterpillars subjected to a 4‐day starvation period. Then, we used qPCR to measure relative bacterial abundances at each instar. Our results indicate larval gut bacterial composition and abundance are predominantly diet‐driven, with a myriad of bacterial genera seemingly transiently present. However, several genera (e.g., Ralstonia, Pelomonas, and Cutibacterium) appear to be more permanent fixtures, presumably colonizing and proliferating in the digestive tract. Moreover, some bacterial genera co‐occur, forming non‐random associations that may be indicative of functional synergies. Overall, this study advances our knowledge of lepidopteran gut microbial dynamics and provides valuable information for an emerging invertebrate model.

Abstract The nutritional regimens of wasp parasitoids can influence the body size of their progeny and their parasitization capacity. This study aimed to evaluate the impact of food resources (glucose, honey, and no food control) on the body size of offspring and the parasitization capacity of Paracentrobia subflava (Girault) (Hymenoptera: Trichogrammatidae), an egg parasitoid of the corn leafhopper pest Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae). Female P. subflava were exposed to D. maidis eggs for 72 h under three feeding treatments: glucose, honey, and no food control. The body size of the emerged offspring was measured, and parasitization capacity was evaluated by assessing the abundance, rate of parasitism, and emergence rate of P. subflava. The results showed that female offspring from mothers fed with glucose or honey had significantly larger head sizes than offspring from unfed mothers. Male offspring from fed mothers exhibited longer forewings than those from unfed mothers. However, no significant differences were observed in the total abundance of egg parasitoids, parasitism rates, or emergence rates across the feeding treatments. These findings suggest that sugar‐based diets affect the size and shape of offspring body structures in P. subflava but do not impact their parasitization capacity, highlighting the proovigenic nature of this species.

Abstract Gut bacterial composition is closely associated with the food intake and developmental age of herbivorous insects. In this study, we aimed to investigate the diversity of larval gut bacteria in different instar stages of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) feeding on different hosts. Gut bacterial DNA was extracted from the 1st, 2nd, 3rd, and 4th instar larvae of T. absoluta feeding on tomatoes, potatoes, and wolfberries for three generations. Subsequently, diversity and richness of gut bacteria were analyzed via the second‐generation Illumina MiSeq high‐throughput sequencing. Alpha diversity index analysis revealed the highest diversity and abundance of gut bacteria in the T. absoluta larvae fed wolfberry and potato leaves, respectively. The highest gut bacterial diversity and richness were observed in the 1st‐instar larvae feeding on potato and tomato leaves. Tuta absoluta feeding on wolfberry leaves exhibited the lowest gut bacterial diversity in the 1st‐instar stage and highest abundance in the 2nd‐instar stage. Proteobacteria was the dominant phylum in the gut bacteria of stages 1–4 instar larvae feeding on different host plants. The dominant genus was Enterobacter (60.1%) in the 4th‐instar T. absoluta larvae feeding on tomatoes and Wolbachia in those feeding on other plants. PICRUSt2 gene function prediction revealed that the larval gut bacteria of T. absoluta played essential roles in food digestion and nutrient supply. Specifically, Wolbachia may enhance nucleotide metabolism in T. absoluta feeding on potatoes. Overall, this study provides a basis to explore the interactions of T. absoluta with gut bacteria and suggests directions for its adaptive evolution and integrated management.