Bumble Bees

Studies on Scandinavian Bwmble Rees 37SUBGENUS BOMBU,S LATREILLE(s.s.)Bombus Latreille, 1802a, p. 385, 1802b, p. 437.Proposed as a genus. Type-species Apis terrestrisLinnaeus. Monobasic.(Bremus Jurine, 1801, p. 164. Proposed as agenus. Type-species Bremus terrestrzs (Linnaeus)- Bombus terrestris (Linnaeus) by designation ofMorice & Durrant, tr915. Generic name invalidated,Int. Com. Zool. Nomen., Opinion 135,1939. Leucobornbus Dalla Torre, 1880, p. 40, typespeciesBombus terrestrls (Linnaeus) by designationof Sandhouse (1943). Terrestribombzs Vogt,l9ll, p. 55, type-species Bremus terrestris (Linnaeus)- Bornbus terrestris (I-innaeus) by designationof Frison (1927).)Queen, worlcerHead slightly shorter than wide, occasionallyas long as wide. Malar space hardly to markedlyshorter than distal width, about as long as AB(longer in B. sporadicus Nylander, just shorterthan Ar+'). Disc of clypeus flattened anteriorlyand just shorter than distal width, with ratherdense punctures of various size throughout, withwell-defined impressions produced inwards andalmost meeting in the middle of anterior edge.Labral furrow well-defined, nearly one third aswide as labral width; labral tubercles deeply depressed(Fig. l2A), angled at inner end; labrallamella rather strongly curved (less so in B. sporadicus),slightly rvider than furrow. Mandible withoutbasal keel (indication of keel in B. sporadicus) ,with distinct sulcus obliquus and prorninent incisuralateralis, being almost semicircular in unwornspecimens. Eyes directed in front of posteriormandibular condyle. Supra-orbital line touchinglateral ocelli or just transecting them dorsally.Mid-basitarsus with alrnost right rounded distaldorsal angle (Fig. lzc). Hind tibia feebly or notalutaceous, dorsal inner distal angle slightly tomoderately produced; hind basitarsus abouttwice as long as greatest width of the segment(slightly longer in B. sporadicus), posterior edgemore or less curved (Fig. 12T)), longest hairs inposterior fringe markedly shorter than half thegreatest width of the segment.There is a distinct difference in size betweenthe queen and the worker caste (Lsken l96la).MaleHead slightly shorter than wide. Malar spacehardly longer than distal width or equal to thiswidth, longer than A, but shorter than Ar+r.Clypeus not longer than distal width. Mandiblebifid with ventral tooth broader than dorsal one.Eyes directed in front of posterior mandibularcondyle. Ocelli usually situated on a line. Antennaerather short, Au-r, individually l1/2 times thedistal width or hardly so, almost parallel-sided(Figs. 28A, 29A). Hind tibia slightly convexthough outer surface flattened or somewhat impressedtowards posterior margin, bare except.forat rnost proximal third being covered with sparsehairs of various length; posterior and anteriorfringes of the segment shorter than twice thedistal width; posterior fringe of hind basitarsusshorter than distal width. St' and genitalia (Figs.288-D , 298-D); gonostylus transverse with inwardlydirected spine, penis valve trvisted, distallyconvoluted, flaring.Scandinavian speciesThe subgenus is represented by a total of fourScandinavian species, viz. B. lucorum (Linnaeus),B. magnus Vogt, B. sporadicus Nylander andB. terrestris (Linnaeus).Taxonontical remarksThe four species present srnall sclerotic differencesand display a fairly uniform yellow-bandedcolour pattern which mainly differs in the yellowshade, in details in the extension of yellow hairsand in the length of the hairs (Kri.iger 1950, 1954,1956, 1958). Overlapping variations in diagnosticcharacters and fading of yellow hairs often preventreliable determinations of workers and males,An exception is B. sporadicLts) where sex andcaste are identified by several stablc features, cf.the description below.