The first record of the Far Eastern grass-carrying wasp Isodontia nigella (F. Smith, 1856) (Hymenoptera: Sphecidae: Sphecinae) from the Crimea

Abstract

Isodontia nigella (F. Smith, 1856) is native to the Eastern Palaearctic, Oriental region, and Australia. A sheaf of reed canes installed as a trap nest in the Crimea was occupied with 73 nests of this species in 2021. The nests contained one to eight cells separated by partitions made of packed fragments of grass stalks and blades; the closing plug was made of the same materials. In some cases, there was no visible partition between two subsequent cells. The prey consisted of three orthopteran species with the predomination of the tree cricket Oecanthus pellucens (Scopoli, 1763) amounted to 95.1% of the identified specimens; three to 15 victims were stored per cell. Sex ratio was strongly male-biased, about 1♀:4♂. The species had two generations per year. Prepupae of the second generation overwintered and imagines emerged in 2022: males on 12–19 June, females on 17 June–5 July. Melittobia acasta (Walker, 1839) and an unidentified bombyliid fly were recorded as parasitoids that damaged only three cells. The reproductive success of the wasp was 65.2%; most deaths of the progeny were for unknown causes. This is the first record of I. nigella in Europe, outside its native range. Isodontia nigella is the second invasive species of the genus in Europe after I. mexicana (de Saussure, 1867) and the fifth invasive species of the family Sphecidae in the Crimea.