Taxonomic identification and biological traits ofPlatystethynium triclavatum(Donev & Huber, 2002), comb. n. (Hymenoptera, Mymaridae), a newly recorded egg parasitoid of the Italian endemic pestBarbitistes vicetinus(Orthoptera, Tettigoniidae)

Abstract

The little known fairyfly (Hymenoptera, Mymaridae),Platystethynium(Platystethynium)triclavatum(Donev & Huber, 2002), comb. n. fromPseudocleruchusDonev & Huber, 2002, is newly recorded as an egg parasitoid ofBarbitistes vicetinusGalvagni & Fontana, 1993 (Orthoptera, Tettigoniidae). This bush-cricket is endemic to northeastern Italy (mainly Euganean Hills of Veneto Region), where it has recently become an economically significant agricultural and forest pest. Data on discovery, distribution, and some remarkable biological traits of this gregarious egg parasitoid are presented. Its identification and availability of many well-preserved fresh specimens have made possible to re-definePseudocleruchusDonev & Huber, 2002 syn. n., with type and the only described speciesPseudocleruchus triclavatusDonev & Huber, 2002, as a synonym ofPlatystethyniumOgloblin, 1946 and its nominate subgenus,P. (Platystethynium), and also to describe the brachypterous male ofP. (Platystethynium)triclavatum. It is the first known male for the entire genus. Enlarged mandibles of the megacephalous males are used to chew holes in the hard chorion of the host egg, allowing fully winged females, whose mandibles are strongly reduced and do not cross over, to emerge after mating with the males inside it. Up to 136 individual parasitoids (about 77 on average) can hatch from a single egg ofB. vicetinus, with their sex ratio being strongly female biased (80–97% females per egg).