British Insects: Bumblebees and Cuckoo-bees
Subspecies allenellus Stelfox, celticus Yarrow (pallidus Evans), liepeterseni Loken (misidentified as smithianus and arcticus Smith), orcadensis Richards, scyllonius Richards, and sladeni Vogt.
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. Adults about 13–19 mm long (queens about 18 mm, workers 14 mm, males 14 mm). The hair coats of abdomen and thorax more or less homogeneously coloured or merely shaded darker to lighter (save for a median-dorsal black patch on abdominal segments 1 and 2); predominently sandy- to gingery-brown. Face somewhat longer than wide. The facial hairs of males gingery brown; vertex gingery-brown 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 considerably longer than the fourth. The mid antennal segments of the male each somewhat swollen around the middle underneath. Thorax predominantly ginger-haired; without any black hairs just above the wing bases; not banded (homogeneously brightly light ginger-haired, with no black hairs). 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.
The abdomen cf. that of B. humilis and B. distinguendus: medianly black over the two tergites adjacent to the thorax, otherwise ginger and progressively paler and paler towards the tip. Abdomen not conspicuously patterned to conspicuously patterned; predominently ginger haired; without a contrasting tail; without conspicuous banding between the anterior of the tail and the thorax. The abdomen of females with no black hairs, or these confned to tergite 6. Abdomen without black hairs among the ginger ones. Abdominal pubescence relatively short and regular. 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 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, commoner northwards and westwards. The adults abroad during April to September (females), or July to October (males). Tending to prefer grasslands of tall grasses and scattered flowers, especially legumes, labiates, knapweeds and Bartsia.
General comments. Apart from microscopic details of the male genitalia (see the accompanying illustrations) and (according to Saunders) the male antennae, adults of B. humilis and B. muscorum are distinguishable morphologically only by presence of a few thoracic black hairs near the bases of the wings of the former, and the more velvety appearance of the indumentum of B. muscorum when fresh. The distributions overlap and they are described as having much the same the life histories and habitats; i.e., the two species seem weakly circumscribed..
Illustrations. • British Bombus species (4): Saunders. • 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. http://delta-intkey.com’.