British Insects: Bumblebees and Cuckoo-bees
Subspecies hortorum s. str., subspecies ivernicus Sladen (splendida Stelfox).
Subgenus. Subgenus Megabombus.
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 12–22 mm long (queens about 17–20, workers 11–16, males 14–15). The hair coats of abdomen and thorax conspicuously colour-patterned (usually), or more or less homogeneously coloured or merely shaded darker to lighter; predominently when unpatterned, more or less all-black (melanism being fairly common). Face relatively long; much longer than wide. The facial hairs of males 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 tongue relatively long, reaching the apex of the abdomen when fully extended (the distinctively long tongue is commonly 1.5 cm, sometimes reaching 2 cm). The mandibles of males with a blackish beard. The mandibles of the females round-ended, not oblique. Antennae of the male with the third segment at least as long as the fifth; with the third segment considerably longer than the fourth. Thorax banded; black across the middle, with pale anterior and posterior bands. The anterior yellow thoracic band wider than the posterior one. The light thoracic hairs mid-yellow, or mustard yellow, or lemon-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; long haired along the hind edge to the proximal end. 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 black, with an anterior yellowish band and a whitish tail. Abdomen conspicuously patterned; with a contrasting tail. The tail white to greyish white. Abdomen conspicuously banded between the anterior of the tail and the thorax; with a pale band adjacent to the thorax (this extending from the first tergite onto the middle of the second). Abdominal pubescence relatively long, uneven and somewhat ragged. Sternite 2 of females flat between the anterior and posterior margins. Sternite 6 of females without a median keel.
Male genitalia. The sagittae rather straight; externally finely serrate beneath the apex; apices narrow and straight, rounded and scarcely oblique. The ends of the claspers much expanded to somwhat expanded; dark and horny; conspicuously emarginate and toothed; with the volsella readily visible at their ends.
British representation. Recorded from England, Wales, Mainland Scotland, Hebrides, Orkney, Shetland, Channel Isles, and Ireland. Widespread throughout the British Isles, in divers habitats including gardens. The adults abroad during March to September (females), or June to September (males).
General comments. The adult insects of the common B. hortorum are often not reliably separable morphologically from those of the scarce B. ruderatus, although genuinely all-black specimens (as distinct from dark ones with white tails) are perhaps all referable to the latter..
Illustrations. • B. hortorum: queen, worker and male (photo). • 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’.