British Insects: Bumblebees and Cuckoo-bees


L. Watson and M. J. Dallwitz

Psithyrus Lepeletier

Allopsithyrus Popov, Ashtonipsithyrus Fernald, Fernaldaepsithyrus Fernald, Metapsithyrus Popov.

Cuckoo Bees.

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.

Adult morphology. Adults about 14–22 mm long. The mandibles of the females obliquely-ended. Antennal segments (10–)12 (females), or (10–)13 (males). Thorax banded, or not banded (black and unpatterned, or patterned black and greyish, black and pale brownish or black and reddish brown). Closed fore-wing cells 6–10. 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 patterned black-and-orange or reddish orange, black-and-white, or black and grey. Dorsally visible abdominal segments 6 (females), or 7 (males). Abdomen conspicuously patterned. Sternite 6 of females with ventro-lateral keels.

Male genitalia. The ends of the claspers pale and soft.

British representation. 6 species in the British Isles (with two subspecies of P. campestris); recorded from England, Wales, Mainland Scotland, Hebrides, Orkney, Shetland, Channel Isles, and Ireland. Throughout the British Isles.

General comments. The adult males have no sting and bigger eyes than the females, as well as 13-segmented antennae that are longer than the 12-segmented ones of females. In addition to details of the hind tibiae (q.v.), Psithyrus adults differ from those of Bombus in the often more heavily pigmented wings; the female abdomen is more pointed, somewhat less hairy and much harder and does not exude wax between its segments, and the mandibles are more pointed (for killing) than toothed..

Illustrations. • Psithyrus rupestris (Black-winged Bumble-bee: B. Ent. 468). • Psithyrus rupestris (detail: B. Ent. 468). • Psithyrus rupestris (dissections: B. Ent. 468). • Psithyrus rupestris: B. Ent. 468, legend+text. • Psithyrus rupestris: B. Ent. 468, text cont.. • Psithyrus rupestris, P. vestalis, P. campestris, P. sylvestris, P. barbutellus: Saunders. • Comparing females of P. campestris and P. rupestris with their hosts (B. pascuorum and B. lapidarius). • Male genital capsules of Bombus and Psithyrus.

To view illustrations with legends giving names in current use, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa, as well as source references and other relevant material.

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