Social and colonial spiders as model systems for host-symbiont interactions at different levels of organization.

Digging mammals function as ecosystem engineers by altering soil structure, influencing nutrient cycling and shaping vegetation communities. The widespread decline of these taxa globally, driven by habitat loss and introduced predators, has triggered cascading ecological effects, yet the consequences for soil-dwelling insect communities remain poorly understood. Insects, many of which have subterranean larval stages, provide essential functions such as pollination, decomposition and nutrient cycling, making them ideal indicators for evaluating the restructuring of ecological communities following mammal reintroductions. Here, we used data from a long-term experimental mammal exclusion study within a predator-free sanctuary (Scotia Wildlife Sanctuary) in south-eastern Australia to test how the reintroduction of digging mammals affects the structure and composition of insect communities emerging from soil. We sampled insects using emergence traps across replicated plots of mammal reintroduction, exclusion, and procedural control in 2010 and in 2018, 8 years after fence installation. While variation in digging activity (indexed by pit density) did not significantly affect richness or biomass of soil-emerging insect taxa, areas with digging showed reduced insect abundance. Hierarchical modelling of taxa communities revealed that parasitoid wasps (Hymenoptera) and predatory robber flies (Diptera: Asilidae) were strongly associated with plots without digging activity, likely reflecting sensitivity to direct predation or nest disturbance. No herbivorous beetle taxa showed a statistically supported association with treatment, indicating that negative associations with digging activity were restricted to specific parasitoids and predatory groups, rather than representing a consistent trophic-wide response. Our findings therefore indicate that the reintroduction of ecosystem engineers alters insect assemblages, potentially cascading through to multitrophic interactions and ecosystem functioning. This is important because it (1) suggests there may have been profound effects of the widespread loss of ecosystem engineers on ecosystems across the Australian continent; and (2) highlights that whole-of-ecosystem knowledge is critical to getting rewilding right. We emphasise the importance of thorough, long-term ecological monitoring of invertebrate assemblages to inform mammal reintroduction and restoration efforts, ensuring they align with broader ecosystem management objectives.

The fall armyworm (FAW), Spodoptera frugiperda, is a major pest native to the Americas that damages various crops. In recent years, its distribution has expanded worldwide. After invading mainland Japan in 2019, it primarily caused severe damage to corn crops. We have found an egg parasitoid wasp, Telenomus remus, which is present in Japan and attacks FAW. This study investigated the life history characteristics of T. remus in southern Kyushu, Japan, using S. litura, as a host. The lower developmental threshold temperature and thermal constant were found to be 14.0 °C and 143.1 degree-days, respectively. T. remus occurrence was monitored throughout the year from April 2024 to April 2025, using the sentinel prey method with S. litura eggs. While a peak in occurrence was observed from summer to autumn, adults retained reproductive activity even in winter, despite average temperatures being well below T0. Photoperiod had no effect on the development of this species, and no diapause was observed at any developmental stage. When introduced to S. litura eggs and placed outdoors at various times from autumn to early winter 2024, adult T. remus wasps emerged the following spring, suggesting that T. remus can overwinter in various developmental stages. Based on these results and annual temperature data for the study site, this species is estimated to undergo 13 generations per year.

EC-isHCR: A rapid method for in situ hybridization chain reaction in diverse animal samples.

Estimating the number of insect species on Earth is a daunting challenge. The current consensus estimate-about six million species-is likely far too low, as we will show. Our estimate of the global number of insect species rests on a sample of more than 1,600,000 DNA-barcoded insect specimens representing 53,945 species from 15 "core" Malaise traps deployed in dry forest, cloud forest, and rainforest ecosystems of the Área de Conservación Guanacaste (ACG) in Costa Rica. Even this massive sample fails to reveal the full extent of ACG insect species richness. To estimate total ACG insect richness, we adjust the observed count of insect species by an "undersampling ratio," computed for a hyperdiverse subfamily of parasitoid wasps (Braconidae: Microgastrinae). The ratio compares microgastrine richness from the core Malaise traps to a lower-bound estimate of true microgastrine richness-including undetected species-based on 21,669 specimens from three sources: the 15 core Malaise traps, 15 "peripheral" Malaise traps spanning all three ecosystems, and 11,373 DNA-barcoded specimens reared from some 1,500 species of microgastrine-parasitized caterpillars (Lepidoptera). To estimate global insect richness, we apply Earth/ACG ratios for tree species and several animal taxa to upscale our estimate of ACG insect richness (nearly 333,000 species). Adopting conservative assumptions, we reach an estimate of 14 to 20 million insect species on Earth, depending on the upscaling group-two to three times the current consensus estimates. Upscaling instead from a point estimate of ACG richness with a wide CI, global estimates reach nearly 30 million species.

Plants release herbivore-induced volatiles that attract parasitoid wasps. Whether plants can distinguish eggs of different insect species and mount targeted indirect defenses remains unclear. Here, we provide evidence that rice exhibits differential responses. Rice responds differently to eggs of its specialist pest species, the striped stem borer (Chilo suppressalis, SSB), from eggs of two generalists, the Asian corn borer (Ostrinia furnacalis, ACB) and the fall armyworm (Spodoptera frugiperda, FAW). Notably, only SSB egg induces a volatile blend that strongly attracts the egg parasitoid Trichogramma japonicum. D-limonene and methyl salicylate (MeSA) were identified as two key attractants contributing to this differential attraction. Mechanistically, the response to SSB eggs triggers an oxidative burst, salicylic acid accumulation, and jasmonic acid suppression, which is associated with the activation of two biosynthetic genes, OsTPS46 and OsPAL3. CRISPR-Cas9 knockout of either gene markedly reduces or even eliminates volatile emission and reduces parasitoid attraction, and exogenous application of the synthetic blend significantly restores this defect. Together, our work provides a detailed analysis of specific genetic and chemical components underlying differential parasitoid attraction in a major crop and identifies a two-gene module that may enable precision biocontrol strategies.

Polydnaviruses (PDV) are domesticated viruses integrated into the genome of parasitoid wasps. During oviposition, female wasps inject into their host both eggs and PDV particles containing wasp DNA circles. Circle-borne genes are expressed in the host and suppress its immune response, ensuring successful development of the wasp larvae. Several dozen distinct circles have been distinguished on the basis of their sequence and location within the wasp genome. Interestingly, these circles display very different propensities to integrate into the caterpillar genome but the factors influencing this variation remain poorly understood. Here, we experimentally quantified and modelled both the number of PDV integrations and the abundance of injected PDV circles in 8 distinct wasp-host systems. Integrations into the host genomes were observed at rates ranging across wasp species from 0.28 to 14.5 integrations per host haploid genome. Our analyses reveal that integration efficiency varies among circles. We particularly highlight a specific circle, referred to as circle 1, which we find to be both the most abundantly injected and the most efficiently integrated, even after controlling for the direct effects of the quantity injected on the total number of integrations. This pattern is compatible with the view that both the quantity and integration efficiency of injected circles may constitute key components of parasitism success. Finally, our analyses indicate that integration efficiency is reduced in non-suitable hosts, suggesting a possible contribution of host factors to the regulation of PDV circle integration.

Effectively harnessing the biocontrol potential of parasitic wasps requires a precise understanding of their interspecific competition and parasitic efficacy. Using the three dominant egg parasitoids of the fall armyworm (FAW; Spodoptera frugiperda)-Trichogramma dendrolimi, Trichogramma chilonis and Telenomus remus (Te. remus)-as a model system, we first analyzed the parasitic competitive relationships, developed an ITS2-based molecular assay for species-specific identification, and then applied this method to analyze the parasitoids' competitive interactions and quantify their parasitic potential. Competition assays demonstrated that Te. remus achieved superior parasitism performance and produced more progeny with its higher female ratio. Furthermore, we established exponential regression models, which accurately correlated ITS2 gene expression levels with parasitism rates, enabling a direct molecular assessment of parasitic activity. Using these models, we quantified the parasitism rates on FAW eggs as 70.25% for Te. remus, significantly higher than the 41.54% for T. dendrolimi and 36.45% for T. chilonis. This research not only provided clear evidence prioritizing Te. remus as a highly effective agent for FAW biocontrol, but also developed a molecular approach for rapid and accuracy parasitoid efficacy assessment contributing to sustainable pest management. © 2026 Society of Chemical Industry.

Copper-based nanoparticles trigger fitness decline in parasitoid wasps via gut microbiota-induced fatty acid dysregulation.

In order to explore the growth, development, and reproductive capacity of the parasitoid wasp, Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae) reared on the pupae of Lasioderma serricorne (Fabricius) (Coleoptera: Ptinidae), the influence of temperature on lifespan, fecundity, development duration, development threshold temperature, and effective accumulated temperature of T. elegans was investigated at 20, 25, and 30 °C and 65 ± 5% relative humidity under dark conditions. Temperature significantly affected the development and reproductive capacity of T. elegans, and the optimum temperature range for T. elegans development was 25 to 30 °C. The adult longevity, developmental duration, and fecundity of T. elegans increased at 25 °C, and decreased at 30 °C, compared to that at 20 °C. The developmental threshold temperature of preoviposition was 9.65 ± 0.86 °C, and the effective accumulated temperature was 247.59 ± 34.47 d °C. The present results provided valuable information for the large-scale rearing of T. elegans with L. serricorne pupae as hosts.

Horizontal gene transfer occurs beyond anecdotal frequencies in metazoans. Among insects, some parasitoid wasps even carry gene delivery agents called polydnaviruses (PDVs). These domesticated viral elements mediate the integration of wasp genes into the genome of parasitized hosts, thereby protecting developing larvae from immune defenses. The frequency of PDV-mediated transfers is sufficiently high that it could be exploited to better characterize the range of organisms attacked by parasitoid wasps. Here, we apply this rationale by screening for the specific molecular footprints of these transfers in 6,814 protostome genomes. We found a total of 6,556 PDV-mediated integrations, all of which were in insects. The distribution of these integrations is highly consistent with the known host range of PDV-encoding parasitoid wasps. Most were found in lepidopterans (6,260 integrations in 303 species)-the main hosts of PDV-encoding wasps-and a few were retrieved in sawflies (139 integrations in 14 species) and leaf beetles (four integrations in two species), also known to be parasitized by some of these wasps. Remarkably, we found a total of 232 integrations in three species of stick insects and one integration in an orthopteran, two insect lineages that have never been reported to be attacked by PDV-encoding wasps. We show that these integrations are mostly recent and that stick insects and sawflies were attacked recurrently by multiple wasp lineages. Overall, our study warrants accounting for stick insects and orthopterans as possible new targets of parasitoid attacks, both in community ecology and in assessments of biological control strategies.

Gut microbial dysbiosis is associated with detoxification impairment in parasitoid wasps exposed to Emamectin benzoate.

In contrast to chemical pest control, biological control (biocontrol) is generally considered evolutionarily stable, with pests rarely evolving resistance to agents such as parasitoid wasps. In 1997, Holt & Hochberg outlined five principles to explain this pattern. Here, we review post-1997 case studies where resistance has contributed to the breakdown of parasitoid-based biocontrol. We evaluate how these examples align with or challenge Holt & Hochberg's framework and propose updates to reflect new findings. While resistance remains rare, reported cases suggest that breakdowns are more likely when pests possess greater standing genetic variation than their parasitoid enemies. We argue that long-term stability depends not just on host constraints but also on the potential for parasitoid virulence to evolve. Finally, we offer practical recommendations for biocontrol practitioners and regulators to minimise the risk of resistance evolution in parasitoid-based systems.

Infochemicals mediating intraspecific (pheromones) and interspecific (kairomones) interactions play critical roles in parasitoid host location. Yet how they interact to guide foraging behavior remains poorly understood. This study investigated chemical communication between the parasitoid wasp, Chouioia cunea and its host, the fall webworm, Hyphantria cunea, with a focus on the integration of conspecific signals and host-derived cues. Volatile collection and gas chromatography-mass spectrometry (GC-MS) analyses identified 14 and five compounds from wasps and parasitized host pupae, respectively. Chouioia cunea females showed significant attraction to odors from both conspecific females and parasitized host pupae in behavioral assays conducted with a Y-tube olfactometer. Further, wasps showed electroantennographic responses to 18 of the 19 identified compounds, as well as attraction to their synthetic blend. However, female wasps showed strong oviposition preference for unparasitized over parasitized pupae. These results demonstrate that C. cunea integrates conspecific pheromones and host-derived kairomones to guide host location, but uses additional cues for oviposition, to avoid superparasitism. These findings provide new insight into parasitoid chemical ecology and serve as a basis for developing improved attractants for biological control. © 2026 Society of Chemical Industry.

Pinyon–Juniper (PJ) woodlands are critical arid habitats that host diverse biotic communities. We examined tree–arthropod relationships across elevational gradients in northern Arizona, comparing foliar and trunk communities on the 2 dominant tree species, pinyon and juniper. Understanding these dynamics is vital for climate-change adaptation and biodiversity management. Using trunk-refugia traps and sweep-netting, we sampled arthropods on trunks and foliage of both hosts and tested how host tree, elevation, and precipitation structured assemblages. We hypothesized (i) trunk and foliar communities would be compositionally distinct; (ii) communities would differ between pinyon and juniper because of host-specific taxa rather than dominance by a single tree species; and (iii) peaks in foliar diversity would occur where cooler, wetter conditions coincided (mid-elevation sites). The study confirmed distinct foliar and trunk communities and strong, taxon-specific host-tree effects. Juniper foliage supported higher foliar richness and diversity in both years, whereas pinyon trunks supported higher arthropod abundance and several trunk-associated taxa. Pinyons and junipers therefore supported unique trunk and foliar assemblages, contradicting previous studies on ground arthropods. We observed host-specific preferences, with spiders, leafhoppers, and parasitoid wasps more common on juniper foliage, while mites were more abundant in pinyon foliage. Climate associations were year- and taxon-specific: precipitation and elevation structured foliar richness in 2019 but were weaker in 2020. Our findings show that host-tree identity was the more consistent predictor in this dataset, whereas elevation and precipitation proxies captured site-level associations with long-term climatic context rather than year-specific weather, providing a spatial baseline for future monitoring under vegetation and climate change.

Increasing our understanding of parasitoid behavioral movement dynamics is critical to improving biological control strategies. The development of miniature harmonic radar (HR) tags, made with superelastic nitinol wire antennas, means tracking parasitoid wasps may now be possible. This study assessed the suitability of using HR tags (weighing ∼135 μg) for tracking individual Diachasmimorpha longicaudata (Ashmead, 1905) wasps. These braconid wasps are endoparasitoids of the larvae of many agriculturally important tephritid fruit fly species. HR tagged female D. longicaudata were found to be flight capable, but a laboratory flight bioassay showed some potential adverse effects of tagging, including slightly decreased cage landing heights and a numerical decrease in flight times. Flight tests in a large outdoor screen cage showed that D. longicaudata had biased landing distributions favoring a darker colored wall. Additionally, an attempt to observe wasp attraction to fruit was not successful. A multi-day experiment conducted in a coffee field demonstrated the feasibility of successfully following tagged wasp movements over time. Tagged D. longicaudata were found to be largely sedentary, with the longest recorded movement paths (sum of all observed moves) remaining under 10 m over a 3-d period. Mean observed movement distance was 2.7 ± 0.4 m with a mean movement rate of 0.11 ± 0.03 m/h (both values exclude wasps that remained in the release tree). This tracking approach is promising for future studies on parasitoid dispersal, chemical ecology, and parasitoid/predator/prey interactions in natural habitats, thus potentially enhancing the efficiency of biological control using D. longicaudata.

A substantial literature has developed on facultative endosymbionts of insects, often portrayed as having large effects on their hosts, ranging from mutualistic to parasitic. The aphid endosymbiont Regiella insecticola occurs naturally in Myzus persicae and has potential biocontrol applications. Here, we examined the effects of native Regiella in two clones of M. persicae from Australia collected two decades apart, to assess whether these effects could explain the persistence of Regiella in natural populations. Genome sequencing revealed > 99.99% similarity between the Regiella strains from these clones. Regiella was stable in laboratory cultures and transmitted horizontally on excised leaves and intact plants. Fitness assays showed Regiella had modest costs to aphid reproduction but provided some benefits under heat stress, with no host-plant-specific effects. Regiella did not impact transmission of turnip yellows virus. Regiella provided strong protection against parasitism by two common parasitoid wasps, Diaeretiella rapae and Aphidius colemani. These findings indicate that while Regiella has limited fitness effects on M. persicae in the absence of parasitoids, its strong protection against parasitism underscores an important ecological function. However, these effects alone are not sufficient to explain the low incidence of Regiella in natural M. persicae populations, despite evidence for horizontal transfer.

ABSTRACTSpiroplasma bacteria are widespread associates of insects, with Drosophila serving as a key model for understanding maternally inherited symbioses. Most research has focused on the poulsonii–citri clade of Spiroplasma, leaving other lineages comparatively understudied. Here, we characterise the symbiosis between the drosophilid Zaprionus kolodkinae and its ixodetis group Spiroplasma (sZko). We assembled a complete genome for sZko, which encodes multiple candidate symbiosis factors, including ankyrin repeat domain proteins and diverse ribosome‐inactivating protein (RIP) toxins typically linked to protective interactions. Notably, the genome also harbours a gene with a predicted ricin B lectin‐binding domain, a candidate for establishing microbe‐insect interactions at the eukaryotic cell surface. Phenotypic assays confirmed maternal inheritance of sZko with no evidence of reproductive parasitic phenotypes. Infected flies were protected against attack by the generalist parasitoid wasp Leptopilina heterotoma. There was no detectable impact of sZko on its host's starvation tolerance, suggesting minimal physiological cost to the host, and this low impact was mirrored for the protective symbiont sHy1 in D. hydei but contrasted with previous results for D. melanogaster. We conclude the Z. kolodkinae–Spiroplasma association is primarily defensive, and genomic analysis raises the possibility that protection involves a novel coupling between lectin‐binding domains and RIPs.

Viruses likely represent the majority of insect symbiotic microorganisms. Yet, viral symbionts and their interactions with insect hosts were less studied, mostly due to technical difficulties stemming from their small size and lack of universal markers. Although viral symbionts are usually perceived as pathogens, there are clear instances in which they are beneficial to their hosts, providing functions that are essential in some cases and conditionally beneficial in others, shaping insect ecology and evolution. This study provides several pieces of the puzzle on the road to understanding the complex interactions within the multi-trophic system consisting of a parasitoid wasp, its mealybug host, and a double-stranded RNA virus. This system may serve as a case study of viruses' effect on insects and broaden our understanding of the possible effects of viruses on other arthropods.

Successful endoparasitism requires parasitoids to overcome the host immune defense, encapsulation. However, the mechanisms governing encapsulation, particularly its initiation, remain poorly understood, limiting our understanding of coevolution between parasitoids and their hosts and constraining the broader application of parasitoids in biological control. Our results showed that Ostrinia furnacalis plasma factor Immulectin-5 (IML-5) is essential for nonself recognition of hemocytic-mediated encapsulation of Macrocentrus cingulum larvae. Upon incubation with host plasma, three OfIMLs specifically bound to the wasp larval surface. Among them, OfIML-5, predominantly expressed in the fat body, was secreted into the plasma and strongly upregulated upon wasp larval exposure. RNAi-mediated knockdown or antibody-mediated neutralization of OfIML-5 significantly impaired host encapsulation ability. Consistently, CRISPR/Cas9 knockout of OfIML-5 decreased the encapsulation rate from 73.5% to 17.9%. Furthermore, OfIML-5 simultaneously binds to the surface of wasp larvae and hemocytes, suggesting that it possibly acts as a recognition factor and adaptor to promote hemocytic encapsulation. Co-immunoprecipitation assays indicated that OfIML-5 interacts with OfIML-3 and may participate in the transduction of nonself signals. Finally, we provide preliminary evidence that miR-34-5p secreted by M. cingulum targets the OfIML-5 gene and suppresses its expression, thereby attenuating host encapsulation. Our results indicate that OfIML-5 interacts with OfIML-3 and may function to transmit nonself signals to hemocytes, thereby promoting encapsulation against parasitoid wasp. Meanwhile, parasitic wasp M. cingulum secretes miR-34-5p, which targets OfIML-5 and suppresses host encapsulation. These findings help clarify the intricate immune interaction strategies between parasitoid wasps and their hosts. © 2026 Society of Chemical Industry.