Abstract
Sclerogibbid wasps are obligate parasitoids of webspinners (Embiodea). Both groups have a particularly scarce geological record and are known since the Cretaceous: there are only four species of webspinners known from Burmese amber, and only two sclerogibbids were described from Barremian Lebanese and Cenomanian Burmese ambers. Here we report transferred genus from Aptian Choshi (Japan) amber and new sclerogibbids from Cenomanian Burmese and Charentese (France) ambers. The taxa described from Burmese amber are: Burmasclerogibba aptera gen. et sp. nov., Cretosclerogibba gen. nov. (with C. antennalis sp. nov., C. contractocollis sp. nov., C. neli sp. nov. and C. rasnitsyni sp. nov.) and Edrossia vetusta gen. et sp. nov. The first European fossil sclerogibbid Gallosclerogibba alnensis gen. et sp. nov. is described from Charentese amber. The holotype of Chosia yamadai Fujiyama, from Choshi amber, is re-described; it appears to be the oldest Laurasian sclerogibbid. The significant abundance and variety of Burmese sclerogibbid wasps (60% of fossil species known worldwide), as proxy of their hosts, were probably caused by the protection granted to them by the silk webs and possibly by the limited predation from ornithuromorph birds or crown-group ants. While all three extant sclerogibbid genera have apterous females, genera with winged females (Cretosclerogibba and Edrossia) dominated in Burmese amber. Small silk galleries from hosts may have favored the preservation of wings in females of Cretaceous sclerogibbids. Most new species described in the present paper, in addition to C. yamadai, are characterized by a very slender neck and a very long frontal process concealing the antennal toruli. These characters disappeared in extant species. We suggest that this loss was caused by a change in the fauna of predators, penalizing species with long neck and rostrum.
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