British Insects: Bumblebees and Cuckoo-bees
Subgenus. Subgenus Subterraneobombus.
Biology. Social insects forming organized communities; the larvae feeding on pollen and nectar gathered and prepared by the adult females. Nesting on the surface of the ground, or only just below.
Adult morphology. Adult queens, workers and males all similar appearance. Adults about 14–21 mm long (queens about 20 mm, workers 16 mm, males 15 mm). Face relatively long; somewhat longer than wide. The facial hairs of males pale yellow and black; vertex pale yellow haired. The facial hairs of females yellow and black; vertex with some yellow hairs among the black ones. The clypeus of females predominantly smooth and shining, the central area with only sparse micro-punctures. The mandibles of the females round-ended, not oblique. Antennae of the male with the third segment at least as long as the fifth. Thorax predominantly ginger-haired; banded (mustard yellow fore and aft, with a broad blackish median band); black across the middle, with pale anterior and posterior bands; the light thoracic hairs mustard yellow. The outer surface of the hind tibiae of females with a conspicuous pollen basket, in the form of an elongate, shiny, hairless, area framed by stout hairs. The hind tibiae of the males having a fringe of long hairs along the outer margin. Mid basitarsus of females with the distal-posterior margin extended to form a sharp angle of less than 45 degrees, or produced into a narrow tooth or spine. Scutellum of females at least partly pale-haired. Scutellum of males pale- or predominantly pale-haired.
The abdomen medianly black over the two tergites adjacent to the thorax, otherwise mustard-yellowish and progressively paler towards the tail. Abdomen not conspicuously patterned to conspicuously patterned; without a contrasting tail; without conspicuous banding between the anterior of the tail and the thorax; without black hairs among the ginger ones.
Male genitalia. The sagittae rather straight to curved inwards around the spatha; externally dentate laterally above the middle; apices apically truncate, turned outwards and produced laterally into a transverse subquadrate process. The ends of the claspers not expanded; dark and horny; not or only slightly emarginate, without teeth; with the volsella readily visible at their ends to with the volsella inconspicuous.
British representation. Recorded from Mainland Scotland, Hebrides, Orkney, and Ireland. Formerly widespread over in the British Isles, especially coastally, but now seemingly confined to the north of Scotland, Hebrides, Orkney and west Galway. The adults abroad during May to September (females), or August to September (males). In flower-rich, open places.
General comments. Hair coat long.
Illustrations. • British Bombus species (3): Saunders. • 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. http://delta-intkey.com’.