Nest structure, associated parasites and morphology of mature larvae of two European species of Pseudoanthidium Friese, 1898 (Hymenoptera, Megachilidae)

Abstract

The bee genusPseudoanthidiumis represented by nine species in Europe. Of these nine species,Pseudoanthidium nanumis the most widespread, occurs mainly in xerothermic open habitats and creates nests in various cavity types. In this study, we provide information on the nest structure of this species in reed stalks and oak galls and about its parasitic species. We provide the first report ofP. nanumas a host ofXylophrurus augustus(Ichneumonidae). The biology of the much rarer related speciesPseudoanthidium tenellumis described here for the first time. This species occurs in terrestrial reed beds and wet meadows with the presence of reed galls and flowering plants in the family Asteraceae and is rare throughout its entire distribution area. This species nests inside reed galls induced byLiparafrit flies, and the nest structure is very similar to that ofP. nanum. We report new parasitic species of this bee, namely, the cuckoo beeStelis punctulatissima, the predator-inquilineGasteruption nigrescensand two parasitoids,Leucospis biguetinaandMiltogramma punctata. This bee collects pollen mainly from wetland plants inBidensandPulicaria. We also describe mature larvae of both species. The larvae do not differ greatly from one another; only the shape of mandibles and sclerotisation of mouthparts are slightly different. Further research should address the ecological requirements ofP. tenellum, a poorly understood reed gall inquiline.