First biological observations of Megischus ranjithi Binoy, Santhosh & Girish Kumar, 2020 (Hymenoptera: Stephanidae), with evidence of a probable host association and a range extension in Peninsular India

Stephanid wasps are among the least studied parasitoid Hymenoptera, and little is known about the biology or host associations of most species occurring in the Oriental region. Megischus ranjithi Binoy, Santhosh & Girish Kumar, 2020, described from Tamil Nadu, is one of only two species of the genus currently known from India, and its natural history has remained unknown since its description. During surveys carried out in Karnataka between 2025 and 2026, several individuals of M. ranjithi were reared from dead branches of Acacia chundra and other Acacia species infested with wood-boring beetles. Examination of the infested wood consistently revealed buprestid larvae occupying the same galleries as pupae and newly emerged adults of M. ranjithi. The repeated co-occurrence of the parasitoid wasp with buprestid larvae very likely suggests that members of Buprestidae are the probable hosts of this species, as no other hosts were sighted throughout two consecutive years of the study period. The collections also extend the known distribution of M. ranjithi to Karnataka, representing the first record of the species from the state. These observations provide the first biological information available for M. ranjithi and identify Acacia as the plant substrate supporting its probable host association. Given the limited knowledge of the biology of Stephanidae in the Oriental region, the present study contributes new natural history information for one of India's least-known crown wasps and provides a basis for future studies on host specificity, parasitoid biology, and the ecology of wood-associated Hymenoptera.