The present study, conducted in West Bengal, India, explored the unique ‘multi-chambered’ appearance of certain spider eggs, leading to the discovery of gregarious parasitism in the idiobiont endoparasitoid Idris Förster (Hymenoptera: Scelionidae). Little is known about the roles of parasitoid Hymenoptera in regulating spider populations. Phylogenetic analysis based on the mitochondrial cytochrome c oxidase I marker identified five distinct species of Idris. These five gregarious species, identified in association with various spider hosts across multiple locations during a two-year study, offer new insights into host-parasitoid interactions and their adaptability in different host systems. Additionally, six novel host associations between egg parasitoids and five spider species from two families are documented. Under the family Scelionidae, Idris is the second genus, after Telenomus Haliday, adapting to gregarious development. Our findings emphasize the existence of diverse trophic interactions and life strategies in nature that are yet to be documented.

The members of tribe Baeini (Hymenoptera: Scelionidae) are predominantly parasitoids of spider eggs. In India, baeine wasps are represented by five genera- Baeus Haliday, 1833, Idris Förster, 1856, Ceratobaeus Ashmead, 1893, Odontacolus Kieffer, 1910 and Neoceratobaeus Rajmohana, 2014. Of the above, Neoceratobaeus is comparatively rare, lesser-known and endemic to India. This study is the maiden attempt to assess Neoceratobaeus as a distinct genus under the tribe Baeini using DNA barcode data. Phylogenetic analysis of mitochondrial COI and nuclear 28S rRNA genes supports its prior classification as a new genus based on morphology.

The present study from Indian Sundarbans, reports a new host-parasitoid association of Spodoptera pecten Guenée (Lepidoptera) and Telenomus remus Nixon (Hymenoptera). T. remus was identified integrating both morphological and molecular studies, while identification of S. pecten was based on molecular data (mt COI) obtained from reared larvae. The study confirms the natural occurrence of T. remus populations in Indian Sundarbans, with S. pecten as their host. Maximum likelihood trees based on the mt COI DNA gene sequences were generated for T. remus, and S. pecten to confirm the conspecificity. Further, the work also reports Musa sp. as a new host plant of S. pecten.