British Insects: Bumblebees and Cuckoo-bees
B. derhamellus (Kirby).
Subgenus. Subgenus Thoracobombus.
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, or females and workers similar in appearance, the males somewhat different (the male thorax greyer fore and aft). Adults about 12–18 mm long (queens about 17 mm, workers 15 mm, males 13 mm). The hair coats of abdomen and thorax all black except for a contrasting abdominal tail to not all black anterior to a contrasting abdominal tail. Face relatively short (that of the male clothed with black hairs); somewhat longer than wide. The facial hairs of males yellow and black, or black, or greenish yellow and black; vertex black haired. The facial hairs of females black; vertex black haired. The clypeus of females with scattered large to medium punctures over most of its surface, including much of the central area. The mandibles of the females round-ended, not oblique. Antennae of the male with the third segment shorter than the fifth; with the third segment considerably longer than the fourth (the 5th almost as long as the 3rd and 4th together). Thorax not predominantly ginger-haired; banded (in some males only), or not banded (black, in females); when banded, i.e in some males, black across the middle, with pale anterior and posterior bands; the light thoracic hairs greenish grey. 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; pollen basket framed by red or orange-red 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.
The abdomen black or blackish (in males greyer), with a faint narrow greyish band adjacent to the red tail. Abdomen conspicuously patterned; with a contrasting tail. The tail over tergites 4–6, orange-red. Abdomen faintly to fairly conspicuously banded between the anterior of the tail and the thorax (in some males), or without conspicuous banding between the anterior of the tail and the thorax; in males, when banded, with a pale band across the middle (this yellowish dark grey). Sternite 2 of females with a weak rounded transverse ridge between the anterior and posterior margins.
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. The ends of the claspers much expanded; dark and horny; conspicuously emarginate and toothed; with the volsella readily visible at their ends.
British representation. Recorded from England, Wales, Mainland Scotland, Channel Isles, and Ireland. Southern England and Wales, southern and north coastal Ireland, and an extreme northerly population on the Inner Hebrides. The adults abroad during April to August (females), or July to August (males).
Illustrations. • British Bombus spp. (1): 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’.