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The Ichneumonoidea is a vast and important superfamily of parasitic wasps, with some 60,000 described species and estimated numbers far higher, especially for small-bodied tropical taxa. The superfamily comprises two cosmopolitan families - Braconidae and Ichneumonidae - that have largely attracted separate groups of researchers, and this, to a considerable extent, has meant that understanding of their adaptive features has often been considered in isolation. This book considers both families, highlighting similarities and differences in their adaptations. The classification of the whole of the Ichneumonoidea, along with most other insect orders, has been plagued by typology whereby undue importance has been attributed to particular characters in defining groups. Typology is a common disease of traditional taxonomy such that, until recently, quite a lot of taxa have been associated with the wrong higher clades. The sheer size of the group, and until the last 30 or so years, lack of accessible identification materials, has been a further impediment to research on all but a handful of 'lab rat' species usually cultured initially because of their potential in biological control. New evidence, largely in the form of molecular data, have shown that many morphological, behavioural, physiological and anatomical characters associated with basic life history features, specifically whether wasps are ecto- or endoparasitic, or idiobiont or koinobiont, can be grossly misleading in terms of the phylogeny they suggest. This book shows how, with better supported phylogenetic hypotheses entomologists can understand far more about the ways natural selection is acting upon them. This new book also focuses on this superfamily with which the author has great familiarity and provides a detailed coverage of each subfamily, emphasising  anatomy, taxonomy and systematics, biology, as well as pointing out the importance and research potential of each group. Fossil taxa are included and it also has sections on biogeography, global species richness, culturing and rearing and preparing specimens for taxonomic study. The book highlights areas where research might be particularly rewarding and suggests systems/groups that need investigation. The author provides a large compendium of references to original research on each group. This book is an essential workmate for all postgraduates and researchers working on ichneumonoid or other parasitic wasps worldwide. It will stand as a reference book for a good number of years, and while rapid advances in various fields such as genomics and host physiological interactions will lead to new information, as an overall synthesis of the current state it will stay relevant for a long time.

The tendency of parasitoid wasps to oviposit in a previously parasitised host (superparasitism) has long been considered detrimental to their fitness, until recent evidence showed that it may be an adaptive strategy. The solitary koinobiont parasitoid, Coccygidium luteum, was observed to superparasitise the fall armyworm, Spodoptera frugiperda, under laboratory conditions. This study was conducted to elucidate the oviposition choice between unparasitised and previously parasitised hosts by C. luteum and to determine the effect of superparasitism on progeny development and adult fitness, using fall armyworm larvae as hosts. In a choice assay, previously parasitised and unparasitised hosts were simultaneously exposed to C. luteum for oviposition. Oviposition duration and preference were observed and the influence of superparasitism on the development of immature parasitoids and adult fitness were investigated by exposing host larvae to single, double and triple parasitism at 1 h intervals. Coccygidium luteum readily attacked both unparasitised and previously parasitised hosts without discrimination. However, the time spent ovipositing on the unparasitised host was significantly longer than that on a previously parasitised host. Superparasitism did not significantly affect progeny development and the fitness of adult C. luteum. Offspring development time and size of adult parasitoids were similar in superparasitised hosts compared to hosts that were parasitised once. We conclude that superparasitism in C. luteum will have no effect on its mass rearing for the biological control of S. frugiperda.

The Thai fauna of eleven agathidine genera, i.e., Biroia , Braunsia , Camptothlipsis , Coccygidium , Cremnops , Cremnoptoides , Disophrys , Earinus , Gyrochus , Lytopylus , and Troticus , are revised. 25 species are treated, 20 of which are found in Thailand and five that are likely to occur there. Six new species are described, i.e., Braunsia chaweewanae Sharkey, sp. n., Camptothlipsis annemariae Sharkey, sp. n., Camptothlipsis sheilae Sharkey, sp. n., Coccygidium mastigion Sharkey, sp. n., Coccygidium phaeoscapos Sharkey, sp. n., and Cremnoptoides yui Sharkey, sp. n.The following new synonomies are proposed: Isopronotum seminigripenne Enderlein, 1920, Isopronotum tricolor Enderlein, 1920, Biroia soror van Achterberg & Long, 2010, are all synonymized with Biroia fuscicornis (Cameron, 1903). Braunsia pumatica van Achterberg & Long 2010 is synonymized with Braunsia fumipennis (Cameron, 1899). Braunsia devriesi van Achterberg & Long 2010is synonymized with Braunsia smithii (Dalla Torre, 1898). Cremnops malayensis Bhat, 1979 and Agathis nigritarsus Cameron 1899 are synonymized with Cremnops desertor (Linnaeus, 1758). Disophrys macilifera van Achterberg & Long 2010 is synonymized with Disophrys strigata Enderlein, 1920. Disophrys quymanhi van Achterberg & Long 2010 is synonymized with Disophrys subfaciata (Brullé, 1846). Agathis burmensis Bhat & Gupta (1977) is synonymized with Lytopylus ebulus (Nixon, 1950). Disophrys ornatipennis Cameron 1905 is transferred to Gyrochus ornatipennis Cameron, 1905, comb. n. Agathis flavipennis Brullé is transferred to Gyrochus flavipennis (Brullé, 1846), comb. n. A key to the genera of Thai Agathidinae and keys to the species of each genus with multiple species are presented.

Parasitoid wasp venoms represent highly specialized biochemical arsenals that evolved to manipulate host physiology and ensure successful development of the parasitoid offspring. However, the molecular targets and mechanisms underlying this complex host modulation remain poorly understood. To address this, we employed an AI-driven discovery pipeline, integrating the sequence-based predictor D-SCRIPT with the structural modeler AlphaFold3, to characterize LjSPI-1, a venom serpin from Liragathis javana. This computational workflow highlighted a previously unreported candidate partner—a host serine carboxypeptidase (Chr09G02510). Crucially, we detected a direct physical interaction between these two proteins through both in vitro pull-down and in vivo yeast two-hybrid assays, supporting this AI-prioritized interaction under experimental conditions. Our study identifies a high-priority molecular pairing and demonstrates the utility of an AI-guided strategy for uncovering candidate targets of venom proteins. In addition, guided by the predicted biochemical role of Chr09G02510, we propose several plausible physiological hypotheses linking this interaction to host peptide metabolism and immune modulation. These hypotheses serve as a conceptual basis for future mechanistic and toxicological investigations.

Many parasites modify their host behaviour to improve their own transmission and survival, but the proximate mechanisms remain poorly understood. An original model consists of the parasitoid Dinocampus coccinellae and its coccinellid host, Coleomegilla maculata; during the behaviour manipulation, the parasitoid is not in contact with its host anymore.We report herein the discovery and characterization of a new RNA virus of the parasitoid (D. coccinellae paralysis virus, DcPV). Using a combination of RT-qPCR and transmission electron microscopy, we demonstrate that DcPV is stored in the oviduct of parasitoid females, replicates in parasitoid larvae and is transmitted to the host during larval development. Next, DcPV replication in the host’s nervous tissue induces a severe neuropathy and antiviral immune response that correlate with the paralytic symptoms characterizing the behaviour manipulation. Remarkably, virus clearance correlates with recovery of normal coccinellid behaviour. These results provide evidence that changes in ladybeetle behaviour most likely result from DcPV replication in the cerebral ganglia rather than by manipulation by the parasitoid. This offers stimulating prospects for research on parasitic manipulation by suggesting for the first time that behaviour manipulation could be symbiont-mediated.

Abstract Parasitoids introduce various virulence factors when parasitism occurs, and some taxa generate teratocytes to manipulate the host immune system and metabolic homeostasis for the survival and development of their progeny. Host-parasitoid interactions are extremely diverse and complex, yet the evolutionary dynamics are still poorly understood. A category of serpin genes, named CvT-serpins, was discovered to be specifically expressed and secreted by the teratocytes of Cotesia vestalis, an endoparasitoid of the diamondback moth Plutella xylostella. Genomic and phylogenetic analysis indicated that the C. vestalis serpin genes are duplicated and most of them are clustered into 1 monophyletic clade. Intense positive selection was detected at the residues around the P1–P1′ cleavage sites of the Cv-serpin reactive center loop domain. Functional analyses revealed that, in addition to the conserved function of melanization inhibition (CvT-serpins 1, 16, 18, and 21), CvT-serpins exhibited novel functions, i.e. bacteriostasis (CvT-serpins 3 and 5) and nutrient metabolism regulation (CvT-serpins 8 and 10). When the host-parasitoid system is challenged with foreign bacteria, CvT-serpins act as an immune regulator to reprogram the host immune system through sustained inhibition of host melanization while simultaneously functioning as immune effectors to compensate for this suppression. In addition, we provided evidence that CvT-serpin8 and 10 participate in the regulation of host trehalose and lipid levels by affecting genes involved in these metabolic pathways. These findings illustrate an exquisite tactic by which parasitoids win out in the parasite–host evolutionary arms race by manipulating host immune and nutrition homeostasis via adaptive gene evolution and neofunctionalization.

The Polydnaviridae (PDV), including the Bracovirus (BV) and Ichnovirus genera, originated from the integration of unrelated viruses in the genomes of two parasitoid wasp lineages, in a remarkable example of convergent evolution. Functionally active PDVs represent the most compelling evolutionary success among endogenous viral elements (EVEs). BV evolved from the domestication by braconid wasps of a nudivirus 100 Ma. The nudivirus genome has become an EVE involved in BV particle production but is not encapsidated. Instead, BV genomes have co-opted virulence genes, used by the wasps to control the immunity and development of their hosts. Gene transfers and duplications have shaped BV genomes, now encoding hundreds of genes. Phylogenomic studies suggest that BVs contribute largely to wasp diversification and adaptation to their hosts. A genome evolution model explains how multidirectional wasp adaptation to different host species could have fostered PDV genome extension. Integrative studies linking ecological data on the wasp to genomic analyses should provide new insights into the adaptive role of particular BV genes. Forthcoming genomic advances should also indicate if the associations between endoparasitoid wasps and symbiotic viruses evolved because of their particularly intimate interactions with their hosts, or if similar domesticated EVEs could be uncovered in other parasites.

Day length (photoperiod) and temperature oscillate daily and seasonally and are important cues for season-dependent behavior. Larval diapause of the parasitoid Nasonia vitripennis is maternally induced following a certain number of days (switch point) of a given critical photoperiod (CPP). Both the switch point and the CPP follow a latitudinal cline in European N. vitripennis populations. We previously showed that allelic frequencies of the clock gene period correlate with this diapause induction cline. Here we report that circadian expression of four clock genes—period (per), cryptochrome-2 (cry-2), clock (clk), and cycle (cyc)—oscillates as a function of photoperiod and latitude of origin in wasps from populations from the extremes of the cline. Expression amplitudes are lower in northern wasps, indicating a weaker, more plastic clock. Northern wasps also have a later onset of activity and longer free-running rhythms under constant conditions. RNA interference of per caused speeding up of the circadian clock, changed the expression of other clock genes, and delayed diapause in both southern and northern wasps. These results point toward adaptive latitudinal clock gene expression differences and to a key role of per in the timing of photoperiodic diapause induction of N. vitripennis.

Abstract Miniaturization has occurred in many animal lineages, including insects and vertebrates, as a widespread trend during animal evolution. Among Hymenoptera, miniaturization has taken place in some parasitoid wasp lineages independently, and may have contributed to the diversity of species. However, the genomic basis of miniaturization is little understood. Diverged approximately 200 Ma, Telenomus wasps (Platygastroidea) and Trichogramma wasps (Chalcidoidea) have both evolved to a highly reduced body size independently, representing a paradigmatic example of convergent evolution. Here, we report a high-quality chromosomal genome of Telenomus remus, a promising candidate for controlling Spodoptera frugiperda, a notorious pest that has recently caused severe crop damage. The T. remus genome (129 Mb) is characterized by a low density of repetitive sequence and a reduction of intron length, resulting in the shrinkage of genome size. We show that hundreds of genes evolved faster in two miniaturized parasitoids Trichogramma pretiosum and T. remus. Among them, 38 genes exhibit extremely accelerated evolutionary rates in these miniaturized wasps, possessing diverse functions in eye and wing development as well as cell size control. These genes also highlight potential roles in body size regulation. In sum, our analyses uncover a set of genes with accelerated evolutionary rates in Tri. pretiosum and T. remus, which might be responsible for their convergent adaptations to miniaturization, and thus expand our understanding on the evolutionary basis of miniaturization. Additionally, the genome of T. remus represents the first genome resource of superfamily Platygastroidea, and will facilitate future studies of Hymenoptera evolution and pest control.

Endoparasitic wasps produce several factors, such as polydnavirus, venom and a specialized group of wasp embryonic cells named teratocytes, to condition their hosts and support the development of parasitoid offspring. However, the role of the developing parasitoid larvae in host adaption and regulation remains largely unknown. By analyzing RNA-seq data of Cotesia vestalis , an endolarval parasitoid of the diamondback moth Plutella xylostella , we discovered that most of the larval stage highly expressed genes are associated with nutrient metabolism, including carbohydrate, protein, and lipid metabolism. We also identified hundreds of C. vestalis larvae-secreted proteins. A large proportion of the secreted proteins (126/404) are encoded by larval highly expressed genes. Besides several immune-related proteins, most of the secreted proteins are closely related to carbohydrate, protein, and amino acid metabolism. We further demonstrated that eleven genes linked to amino acid metabolism that encode secretory proteins were upregulated in 2nd instar larvae. These results suggest a relatively positive correlation between gene expression and secreted proteins. In summary, our study presents the secretory proteome of an endolarval parasitoid, highlighting its potential function in nutritional and immune regulation within the host, which would benefit the growth and development of parasitoid progeny.