The host defence of insects includes a combination of cellular and humoral responses. The cellular arm of the insect innate immune system includes mechanisms that are directly mediated by haemocytes (e.g., phagocytosis, nodulation and encapsulation). In addition, melanization accompanying coagulation, clot formation and wound healing, nodulation and encapsulation processes leads to the formation of cytotoxic redox‐cycling melanin precursors and reactive oxygen and nitrogen species. However, demarcation between cellular and humoral immune reactions as two distinct categories is not straightforward. This is because many humoral factors affect haemocyte functions and haemocytes themselves are an important source of many humoral molecules. There is also a considerable overlap between cellular and humoral immune functions that span from recognition of foreign intruders to clot formation. Here, we review these immune reactions starting with the cellular mechanisms that limit haemolymph loss and participate in wound healing and clot formation and advancing to cellular functions that are critical in restricting pathogen movement and replication. This information is important because it highlights that insect cellular immunity is controlled by a multilayered system, different components of which are activated by different pathogens or during the different stages of the infection.

Insects are one of the most successful animals in nature, and entomopathogenic fungi play a significant role in the natural epizootic control of insect populations in many ecosystems. The interaction between insects and entomopathogenic fungi has continuously coevolved over hundreds of millions of years. Many components of the insect innate immune responses against fungal infection are conserved across phyla. Additionally, behavioral responses, which include avoidance, grooming, and/or modulation of body temperature, have been recognized as important mechanisms for opposing fungal pathogens. In an effort to investigate possible cross-talk and mediating mechanisms between these fundamental biological processes, recent studies have integrated and/or explored immune and behavioral responses. Current information indicates that during discrete stages of fungal infection, several insect behavioral and immune responses are altered simultaneously, suggesting important connections between the two systems. This review synthesizes recent advances in our understanding of the physiological and molecular aspects influencing cross-talk between behavioral and innate immune antifungal reactions, including chemical perception and olfactory pathways.

The escalating challenge of resistance to insecticides among agricultural and public health pests poses a significant threat to global food security and vector-borne disease control. This review synthesizes current understanding of the molecular mechanisms underpinning resistance, including well-characterized pathways such as target-site mutations affecting nicotinic acetylcholine receptors (nAChRs), acetylcholinesterase (AChE), voltage-gated sodium channels (VGSCs), and γ-aminobutyric acid (GABA) receptors, and metabolic detoxification mediated by cytochrome P450 monooxygenases (CYPs), esterases, and glutathione S-transferases (GSTs). Emerging resistance mechanisms are also explored, including protein sequestration by odorant-binding proteins and post-transcriptional regulation via non-coding RNAs, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Focused case studies on Aedes aegypti and Spodoptera frugiperda illustrate the complex interplay of genetic and biochemical adaptations driving resistance. In Ae. aegypti, voltage-gated sodium channel (VGSCs) mutations (V410L, V1016I, F1534C) combined with metabolic enzyme amplification confer resistance to pyrethroids, accompanied by notable fitness costs and ecological impacts on vector populations. In S. frugiperda, multiple resistance mechanisms, including overexpression of cytochrome P450 genes (e.g., CYP6AE43, CYP321A8), target-site mutations in ryanodine receptors (e.g., I4790K), and behavioral avoidance, have rapidly evolved across global populations, undermining the efficacy of diamide, organophosphate, and pyrethroid insecticides. The review further evaluates integrated pest management (IPM) strategies, emphasizing the role of biopesticides, biological control agents, including entomopathogenic fungi and parasitoids, and molecular diagnostics for resistance management. Taken together, this analysis underscores the urgent need for continuous molecular surveillance, the development of resistance-breaking technologies, and the implementation of sustainable, multifaceted interventions to safeguard the long-term efficacy of insecticides in both agricultural and public health contexts.

Spodoptera frugiperda is a worldwide generalist pest with remarkable adaptations to environments and stresses, including developmental stage-related behavioral and physiological adaptations, such as diverse feeding preferences, mate seeking, and pesticide resistance. Insects’ odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are essential for the chemical recognition during behavioral responses or other physiological processes. The genome-wide identification and the gene expression patterns of all these identified OBPs and CSPs across developmental stage-related S. frugiperda have not been reported. Here, we screened for genome-wide SfruOBPs and SfruCSPs, and analyzed the gene expression patterns of SfruOBPs and SfruCSPs repertoires across all developmental stages and sexes. We found 33 OBPs and 22 CSPs in the S. frugiperda genome. The majority of the SfruOBP genes were most highly expressed in the adult male or female stages, while more SfruCSP genes were highly expressed in the larval or egg stages, indicating their function complementation. The gene expression patterns of SfruOBPs and SfruCSPs revealed strong correlations with their respective phylogenic trees, indicating a correlation between function and evolution. In addition, we analyzed the chemical-competitive binding of a widely expressed protein, SfruOBP31, to host plant odorants, sex pheromones, and insecticides. Further ligands binding assay revealed a broad functional related binding spectrum of SfruOBP31 to host plant odorants, sex pheromones, and insecticides, suggesting its potential function in food, mate seeking, and pesticide resistance. These results provide guidance for future research on the development of behavioral regulators of S. frugiperda or other environmentally friendly pest-control strategies.