Valeria Palma-Onetto

Cuticular hydrocarbons (CHCs) are central to insect waterproofing and chemical communication, yet their diversity and comparative distribution in termites have not been synthesized comprehensively. Here, we present a systematic review of termite CHCs with emphasis on worker profiles, caste‐level comparisons, and descriptive ecological interpretation. The qualitative synthesis included 28 studies, whereas the filtered statistical dataset comprised 37 worker profiles representing 37 species. Across the reviewed literature, termite cuticles contained a recurrent but variable combination of n‐alkanes, n‐alkenes, alkadienes, alkatrienes, mono‐, di‐, and trimethylalkanes. Species‐level mapping showed that saturated and methyl‐branched hydrocarbons were broadly distributed across the sampled taxa, whereas unsaturated compounds were more unevenly represented across the dataset. Genus‐level synthesis showed that methyl‐alkane‐dominated, olefin‐dominated, and mixed worker profiles occur in different higher taxonomic groups within the sampled dataset. Quantitative comparison of selected worker profiles highlighted broad chemistry in Mastotermes darwiniensis , strong methyl‐branched dominance in Coptotermes formosanus , dimethyl‐rich profiles in Nasutitermes corniger and N. ephratae , and marked alkatriene dominance in Parvitermes wolcotti . Caste‐resolved studies showed that workers, soldiers, nymphs, and reproductives usually share the same broad CHC classes, with caste differentiation arising mainly through quantitative shifts, although reproductives in some taxa also express caste‐associated compounds. Exploratory ecological analyses identified associations between nesting life type and worker CHC composition: drywood/enclosed wood nesters showed fewer dimethylalkanes and more frequent alkatrienes than other life types; but these patterns could not be separated from broad family‐level phylogenetic structure. Overall, the available evidence suggests that termite CHC diversity reflects variation in the relative representation of a recurring chemical toolkit, with exploratory associations between worker CHC composition and nesting life type. Because the current dataset is limited and phylogenetic signal was not formally tested, these interpretations should be considered exploratory.

Food security faces significant challenges due to the growing threat of insect pests and global climate change, making it essential to adopt sustainable agricultural strategies. Plants possess intrinsic defense systems that are activated in response to herbivore attack, including the emission of specialized volatile organic compounds (VOC) known as herbivore-induced plant volatiles (HIPVs). These volatiles aid the foraging of natural enemies (predators and parasitoids), thereby contributing to biological control of pest populations. Harnessing these chemical defense mechanisms offers a promising avenue for pest management, although natural enemy attraction does not necessarily result in pest suppression or increased crop yield. This review synthesizes plant and insect-derived chemical signaling mechanisms with direct relevance to biological control in crop agroecosystems, including field crops, orchards, vegetable systems, and protected cultivation. We emphasize recent applied research while retaining selected foundational studies that established the principal concepts and mechanisms underlying chemically mediated pest management. Considering the importance of chemical signaling in sustainable agriculture, we propose four key research directions: (1) optimizing plant defense induction mechanisms; (2) integrating HIPVs with natural enemy pheromone-based attractants; (3) combining habitat management with the provision of plant-derived food resources; and (4) harnessing plant defenses through breeding and infochemical-based genetically modified crops. Additionally, we examine the potential impacts of environmental stressors on plant–herbivore chemical communication, underscoring their importance for resilient and environmentally sustainable agricultural systems.

The melon fly, Zeugodacus cucurbitae (Coquillett), is a destructive tephritid pest of cucurbit crops, and neonicotinoids remain important tools for its management. Although neonicotinoids primarily target nicotinic acetylcholine receptors (nAChRs), their possible effects on acetylcholinesterase (AChE)-mediated cholinergic homeostasis in Z. cucurbitae remain poorly understood. In this study, we molecularly characterized the Z. cucurbitae Ache gene and evaluated its expression and functional contribution under dinotefuran, acetamiprid, and thiamethoxam stress. Bioinformatics analyses confirmed conserved cholinesterase features, including the FGESAG catalytic motif, catalytic triad, choline-binding site, oxyanion hole, and conserved disulfide-bond residues. Temporal and tissue-specific expression profiling showed high Ache transcript abundance in eggs, third-instar larvae, and adult heads. Larval exposure to LC₅, LC₂₀, and LC₅₀ concentrations of the three neonicotinoids caused dose- and time-dependent mortality and significantly induced Ache expression, with dinotefuran producing the strongest transcriptional response. Parental exposure also impaired F₁ fecundity, hatchability, larval survival, and adult emergence, with acetamiprid and thiamethoxam causing stronger transgenerational effects than dinotefuran. Oral RNAi significantly increased larval susceptibility upon re-exposure to neonicotinoids after 72 h. These findings indicate that Ache contributes to cholinergic stress response and susceptibility modulation in Z. cucurbitae, supporting its possible potential as an RNAi target for integrated pest management (IPM). However, practical utility at the field level requires further evaluation.

Global agricultural production faces unprecedented challenges due to climate crisis, biodiversity loss, and increasing population pressure, while there is a growing demand for sustainable and eco-conscious food production systems. Traditional methods of crop protection like the use of synthetic chemical pesticides are becoming less effective due to the high resistance development in major insect pests. Moreover, their overuse has raised numerous environmental concerns. In this context, RNA interference (RNAi) has emerged as a promising and environmentally friendly alternative to traditional pesticides, with a more sustainable way of managing pests. This review systematically identifies promising RNAi target gene families for insect pest control, particularly key developmental genes. The selected genes were chosen based on demonstrated RNAi efficacy in at least three different insect species, emphasizing their broad applicability and potential impact. It also discusses the translation of RNAi technologies from laboratory research to field applications. It underscores the importance of moving beyond functional gene characterization to improving the efficiency and scalability of RNAi in real-world agricultural systems. This review systematically lists RNAi target genes and delivery methods in insect pests, identifies research gaps, and supports the development of RNAi-based biopesticides.

Same-sex sexual behavior in invertebrates includes interactions such as courtship, mounting, copulation, tandem running, and pair formation between individuals of the same sex. We conducted a systematic synthesis of 222 primary studies and 12 reviews and found published evidence of SSB in approximately 207 species spanning arthropods, mollusks, annelids, echinoderms, nematodes, and flatworms. Although most reports involved insects (approximately 89%), standardized reporting rates suggest this bias reflects research effort rather than true biological prevalence. Observations came from field studies, although several taxa, particularly Diptera and Hymenoptera, were disproportionately represented by laboratory work. Copulation-like interactions were the most frequently reported behavior, followed by courtship and mounting. Where authors proposed explanatory frameworks, mistaken identity or indiscriminate mating was the most invoked interpretation, although adaptive functions and socially mediated explanations were also recurrent. Direct measurements of fitness consequences were rare and yielded mixed outcomes, suggesting that the consequences of SSB are context dependent rather than uniformly beneficial or maladaptive. Overall, the available evidence supports the view that SSB in invertebrates is neither anomalous nor reducible to a single mechanism. Instead, it appears as a heterogeneous component of the behavioral repertoire whose expression is shaped by mating system, study type, and taxonomic history.

Cuticular hydrocarbons (CHCs) are central to insect waterproofing and chemical communication, yet their broad evolutionary pattern in termites has not been synthesized comprehensively. Here, we present a systematic review of termite CHCs with emphasis on worker profiles, caste-level comparisons, and ecological interpretation in a phylogenetic context. The qualitative synthesis included 28 studies, whereas the filtered statistical dataset comprised 37 worker profiles representing 37 species. Across the reviewed literature, termite cuticles contained a recurrent but variable combination of n-alkanes, n-alkenes, alkadienes, alkatrienes, mono-, di-, and trimethylalkanes. Species-level mapping showed that saturated and methyl-branched hydrocarbons are broadly distributed across the termite tree, whereas unsaturated compounds are more unevenly represented and recur in multiple lineages. Genus-level synthesis further showed that dominant worker chemistry is not tightly constrained by phylogeny: methyl-alkane-dominated, olefin-dominated, and mixed profiles all occur across distantly related taxa. Quantitative comparison of selected worker profiles highlighted broad chemistry in Mastotermes darwiniensis, strong methyl-branched dominance in Coptotermes formosanus, dimethyl-rich profiles in Nasutitermes corniger and N. ephratae, and marked alkatriene dominance in Parvitermes wolcotti. Caste-resolved studies showed that workers, soldiers, nymphs, and reproductives usually share the same broad CHC classes, with caste differentiation arising mainly through quantitative shifts, although reproductives in some taxa also express caste-associated compounds. Exploratory ecological analyses indicated that nesting life type explained part of the worker CHC variation: drywood/enclosed wood nesters showed fewer dimethylalkanes and more frequent alkatrienes than other life types. Overall, termite CHC evolution is best interpreted as repeated lineage-specific reweighting of a shared chemical toolkit shaped by both ecology and phylogeny.

Structure, fonction et évolution des glandes exocrines termites: Les termites représentent un groupe d'insectes eusociaux qui vivent dans des colonies contenant des centaines, voire des millions d’individus. Ils sont très abondants, dépassant 6 000 individus par mètre carré sous les tropiques. En raison de leur abondance, les termites représentent une source de nourriture importante pour une grande variété de prédateurs. Les adaptations défensives des termites permettent aux colonies de surmonter avec succès les pressions des prédateurs. Cette réussite s’explique par le développement d’un système de communication complexe opéré par un riche ensemble de glandes exocrines. Pas moins de 20 glandes exocrines différentes sont connues chez les termites. Certaines de ces glandes avaient fait l’objet d’une attention négligeable, n’étant connues que par des observations anecdotiques.L'une d'elles était la glande labrale. Dans cette étude, j’ai examiné la structure et l’ultrastructure du labrum chez des soldats de 28 espèces, des ouvriers de 28 espèces et des imagos de 33 espèces parmi les principaux représentants des termites, ainsi que chez la blatte xylophage Cryptocercus.La glande labrale était présente chez toutes les espèces et castes et comprenait deux régions de sécrétion situées respectivement sur la face ventrale du labrum et la partie dorso-apicale de l'hypopharynx. L'épithélium de la glande était constitué de cellules sécrétrices de classe 1,auxquelles s'ajoutaient des cellules sécrétrices de classe 3 chez les soldats de quelques espèces.Une caractéristique commune des cellules sécrétrices était l'abondance de réticulum endoplasmique lisse (un organite connu pour produire des sécrétions lipidiques et souvent volatiles), de longues microvillosités avec un canal à l'intérieur, qui libèrent la sécrétion à travers une cuticule modifiée. D’après ces expériences sur la structure, l'ultrastructure et le comportement,mes résultats suggèrent que la glande labrale est impliquée dans la communication défensive après une rencontre avec un étranger. D'autre part, d'autres glandes sont étudiées de manière approfondie chez certaines castes mais n'ont pratiquement pas fait l'objet d'attention chez d'autres castes. C'est le cas de la glande frontale, organe sans équivalent parmi les autres animaux. La glande frontale est bien connue des soldats et des imagos, mais elle était peu connue chez les ouvriers. Afin de brosser un tableau complet de l'évolution de cette glande chez les termites et, par conséquent, chez les termites, je l'ai étudiée chez 41 espèces supplémentaires sur l'ensemble des néoisoptères. La glande frontale de ces espèces était formée uniquement de cellules sécrétrices de classe 1 et se présentait comme un épithélium sans réservoir dans tous les cas. Mes données Abstract 151 suggèrent que la glande frontale aurait des voies d'évolution propres à la caste, avec une forme ancestrale épithéliale avec réservoir chez les soldats et les imagos, mais en n’étant qu’un épaississement épithélial chez les ouvriers. Cette étude a été la première à fournir une image complète de la structure des glandes labrale et frontale à travers tous les taxons et castes des termites, fournissant des informations fondamentales pour améliorer notre compréhension de l'évolution et du comportement social des Isoptera.

Aims: We aimed to provide a molecular phylogeny of all currently known and described Labiotermes species to clarify taxonomic relationships, including the synonymy of Paracornitermes , in order to reconstruct the historical biogeography of the genus and investigate the role of specific biogeographic domains in its diversification. Location: South America. Taxon: Termite genus Labiotermes (Isoptera: Termitidae). Methods: A dated Bayesian phylogeny was estimated using complete mitogenomes (14,985 bps) from all species. We performed biogeographic analyses using the BioGeoBEARS R package, testing 12 maximum likelihood models (six default models with and without a time‐stratified dispersal matrix) across eight defined biogeographic units. Results: The genus Labiotermes originated approximately 21 Mya. Our phylogenetic analysis corroborated the synonymy of Paracornitermes with Labiotermes . The species L. labralis , L. guasu , and L. oreadicus formed a monophyletic group sister to all other Labiotermes . The top four best‐fitting models (DIVALIKE+TS, DEC+TS, DEC+TS+j and DIVALIKE+TS+j) showed no significant differences in their estimations. The analysis revealed limited vicariance but multiple sympatric events, particularly within the western Brazilian savanna (Cerrado). Main Conclusions: The Cerrado has been a key center of diversification for Labiotermes , with multiple dispersal events occurring over the last 10 Mya. These findings underscore the dynamic role of the Cerrado in shaping speciation patterns and highlight how Neotropical landscape evolution has profoundly influenced termite biogeography.

Chemical secretions are one of the main defensive mechanisms in insects. The osmeterium is a unique organ in larvae of Papilionidae (Lepidoptera), which is everted upon disturbance, secreting odoriferous volatiles. Here, using larvae of the specialized butterfly Battus polydamas archidamas (Papilionidae: Troidini), we aimed to understand the mode of action of the osmeterium, the chemical composition and origin of the secretion, as well as its defensive efficiency against a natural predator. We described osmeterium’s morphology, ultramorphology, structure, ultrastructure, and chemistry. Additionally, behavioral assays of the osmeterial secretion against a predator were developed. We showed that the osmeterium is composed of tubular arms (made up by epidermal cells) and of two ellipsoid glands, which possess a secretory function. The eversion and retraction of the osmeterium are dependent on the internal pressure generated by the hemolymph, and by longitudinal muscles that connect the abdomen with the apex of the osmeterium. Germacrene A was the main compound present in the secretion. Minor monoterpenes (sabinene and ß-pinene) and sesquiterpenes ((E)-β-caryophyllene, selina-3,7(11)-diene, and other some unidentified compounds) were also detected. Only sesquiterpenes (with the exception of (E)-β-caryophyllene) are likely to be synthesized in the osmeterium-associated glands. Furthermore, the osmeterial secretion proved to deter predatory ants. Our results suggest that the osmeterium, besides serving as an aposematic warning for enemies, is an efficient chemical defense, with its own synthesis of irritant volatiles.