British Insects: Bumblebees and Cuckoo-bees


L. Watson and M. J. Dallwitz

Psithyrus bohemicus (Seidl)

P. distinctus Pérez.

Biology. Solitary insects, parasitic on social bumblebees; the adult populations comprising males and fertile females only; the larvae parasitic in the nests of host Bombus species; hosted by B. lucorum.

Adult morphology. Adults about 15–20 mm long (females about 19 mm, males about 16 mm). Face at least as wide as long, or wider. The facial hairs of males black; vertex black haired. The vertex black haired. The mandibles of the females obliquely-ended. Antennae of the male with the third segment at least as long as the fifth. Thorax banded (black, with a broad pale- or gingery-yellow anterior band, and usually a posterior one as well in males); black posteriorly, with a pale anterior band only, or black across the middle, with pale anterior and posterior bands (usually, in males); the light thoracic hairs lemon-yellow, or mustard yellow, or gingerish yellow, or orange-yellow. The outer surface of the hind tibiae of females with no ‘pollen basket’, strongly and uniformly convex, dull and uniformly covered with stout hairs. The hind tibiae of the males having a fringe of short hairs along the outer margin.

The abdomen black, with a narrow gingerish band (this paler in males) before the white tail. Abdomen conspicuously patterned; with a contrasting tail. The tail white (with yellow side patches at the top). The white tail with yellow side patches anteriorly. Abdomen conspicuously banded between the anterior of the tail and the thorax, or without conspicuous banding between the anterior of the tail and the thorax. Abdomen without a line of yellowish hairs between the black ones and the white tail. Sternite 6 of females without a reflexed spiny process at the tip; without a median keel; with ventro-lateral keels; with large, conspicuous, bulging callosities associated with the ventro-lateral keels; the callosities separate, not coalescing and not visible from above. Sternite 6 of males without black hair-tufts.

Male genitalia. The sagittae curved inwards around the spatha; smooth to the base, neither serrate nor dentate nor hooked externally; apices apically turned outwards, obliquely truncate and minutely hooked externally at the tip, or apically turned slightly outwards and obliquely truncate, not hooked. The ends of the claspers much expanded; pale and soft; conspicuously emarginate and toothed; with the volsella readily visible at their ends (the visible tip fairly broad and somewhat incurving, internally fringed).

British representation. Recorded from England, Wales, Mainland Scotland, Hebrides, Orkney, Channel Isles, and Ireland. Widespread in the British Isles, commoner northwards, in divers habitats. The adults abroad during April to September (females), or June to September (males).

Illustrations. • Male genital capsules of Bombus and Psithyrus.

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Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. British insects: Bumblebees and Cuckoobees. Version: 1st January 2012.’.