Cathepsin L protease, which belongs to the papain-like cysteine proteases family, is an important player in many physiological and pathological processes. However, little was known about the role of cathepsin L in ladybird beetles (Coccinella septempuctata Linnaeus) during diapause. Here, we analyzed the characteristics of cathepsin L (CsCatL) in the females of C. septempunctata and its role during the diapause of the ladybeetle. CsCatL was cloned and identified from beetle specimens by rapid amplification of cDNA-ends (RACE). The cDNA sequence of CsCatL was 971 bp in length, including an 843 bp open reading frame encoding a protein of 280 amino acids. It was identified as the cathepsin L group by phylogenetic analysis. Knockdown of CsCatL by RNA interference led to decreased expression levels of fatty acid synthase 2 (fas 2) genes and suppressed lipid accumulation. Furthermore, silencing the CsCatL gene distinctly reduced diapause-related features and the survival of female C. spetempunctata under diapause-inducing conditions. The results suggested that the CsCatL gene was involved in fatty acid biosynthesis and played a crucial role in the survival of adult C. septempunctata during the diapause preparation stage.

Understanding predator–prey and predator–predator interactions is essential for evaluating the effectiveness of biocontrol agents and developing efficient pest management strategies. This study investigates the effects of prey species, predator life stage, and predator density on the predatory efficiency of the generalist predator Rhynocoris fuscipes (Fabricius) under semi-field conditions. Both the nymphs and adults of R. fuscipes consumed significantly more second-instar larvae of S. frugiperda than larvae of S. litura or M. separata. Notably, fifth-instar nymphs and adults exhibited higher predation capacity (11.75 ± 0.37 and 10.90 ± 0.40 larvae) than fourth-instar nymphs (9.05 ± 0.29 larvae) on S. frugiperda. R. fuscipes demonstrated a Type II functional response at all developmental stages toward each prey species, and fifth-instar nymphs revealed higher attack rates (a = 1.5205 ± 0.0544) on S. frugiperda; additionally, the handling time did not significantly differ among three prey species. It suggests that this predator may be more effective at controlling noctuid populations at low prey densities. As predator age and density increased, intraspecific competition among R. fuscipes also intensified. In a multi-prey system, R. fuscipes showed a marked preference for S. frugiperda over the other two prey species. These findings indicate that the fifth-instar nymphs and adults of R. fuscipes are particularly effective in suppressing early-instar larvae of the three noctuid pests, especially S. frugiperda, at low densities. This study enhances our understanding of the predation capacity and prey preference of R. fuscipes towards the three noctuid pests and provides a foundation for the development of more targeted and efficient pest management strategies using this predator.

Insects that feed on various host plants possess diverse xenobiotic adaptations; however, the underlying mechanisms are poorly understood. In the present study, we used Grapholita molesta, which shifts feeding sites from peach shoots to apple fruits, as a model to explore the effects of shifts in host plant diet on the profiles of cytochrome P450s and the gut bacteria microbiome, as well as their effects on biopesticide adaptation. We found that the sensitivity of the fruit-feeding G. molesta to emamectin benzoate biopesticide was significantly lower than that of the shoot-feeding larvae. We also found that the P450 enzyme activity and the expression of nine cytochrome P450s were enhanced in G. molesta fed on Fuji apples compared to those fed on peach shoots. The survival rates of G. molesta exposed to emamectin benzoate significantly decreased as each of three of four emamectin benzoate-inducted cytochrome P450 genes were silenced. Furthermore, we discovered the gut bacteria dynamics of G. molesta changed with the host shift and the structure of the gut bacteria microbiome was determined by the final diet ingested; additionally, the dysbiosis of the gut microbiota induced by antibiotics could significantly increase the sensitivity to emamectin benzoate. Taken together, our results suggest that the expression of P450s and the composition of the gut bacteria microbiome promote adaptation to emamectin benzoate in G. molesta, providing new insights into the molecular mechanisms underlying xenobiotic adaptation in this notorious pest.

Glutaredoxin (Grx) is a group of redox enzymes that control reactive oxygen species (ROS), traditionally defined as redox regulators. Recent research suggested that members of the Grx family may be involved in more biological processes than previously thought. Therefore, we cloned the AcGrx5 gene and identified its role in A. chinensis diapause. Sequence analysis revealed the ORF of AcGrx5 was 432 bp, encoding 143 amino acids, which was consistent with the homologous sequence of Halyomorpha halys. RT-qPCR results showed that AcGrx5 expression was the highest in the head, and compared with non-diapause conditions, diapause conditions significantly increased the expression of AcGrx5 in the developmental stages. Further, we found that 15 °C low-temperature stress significantly induced AcGrx5 expression, and the expression of antioxidant enzyme genes AcTrx2 and AcTrx-like were significantly increased after AcGrx5 knockdown. Following AcGrx5 silencing, there was a considerable rise in the levels of VC content, CAT activity, and hydrogen peroxide content, indicating that A. chinensis was exposed to high levels of reactive oxygen species. These results suggested that the AcGrx5 gene may play a key role in antioxidant defense.