914 AN INTRODUCTION TO ENTOMOLOGY 



EE. Posterior metatarsi elongate and dilated. Some of the hairs, 

 especially of the thorax, plumose. A pollen-collecting brush or a 

 corbicula present in the majority of females. Maxillae usually with 

 either the stipes or the lacinia elongate; the latter often very long 

 and covering the tongue; the ocelH never distorted; the abdomen 

 rarely petiolate, and never with a petiole composed only of the first 

 sternite. 



F. Hind tibiae with apical spurs. If the marginal cell {26. Ri + R2) 



is long and slender, reaching nearly to the wing apex, the anal lobe is 



short and fully separated. Cell M4 usually as large as cell ist M2. 



G. Females without a corbicula. First submarginal cell (R + 



1st Ri) rarely divided (by the base of Rs) in which case there is a 



large anal lobe present. In case the marginal cell (2d Ri + R2) is 



longer than the three submarginals, taken together, there is 



usually a well-marked anal lobe in the hind wings. 



H. Wings with two submarginal cells (very rarely less). 



I. Tongue short and the basal segments "of the labial palpi not 

 sheath-like; or the labrum is large and free and uncovered. 

 Females without a ventral pollen-collecting brush; often 

 with a pygidial area. 



J. Tongue short, its apex bifid; labial palpi normal. Fe- 

 male only rarely with a pygidial area. Mesepisternal 

 suture present. Labrum hidden (Prosopinae). p. 993 

 Prosopid^ 



JJ. Tongue long or short, but its apex acute; the labial 

 palpi normal or their basal segments sheath-like. Mes- 

 episternal suture wanting. (Many.) p. 995 . . Andrenid^ 



II. Tongue elongate, the basal segments of the labial palpi 

 sheath-like. Labrum not large and free, usually entirely 

 covered by the clypeus, or if somewhat visible, then strongly 

 inflexed. Females without a pygidial area; those of the 

 non-parasitic species with a ventral pollen-collecting brush. 

 p. 999 Megachilid^e 



HH. Wings with three submarginal cells. Females without a 

 ventral pollen-collecting brush; often with a pygidial area. 



I. Tongue short, its apex bifid. Labial palpi normal. Fe- 

 males rarely with a pygidial area. Mesepisternal furrow 

 present. Labrum hidden. (Colletinse.) p. 993 . . Prosopid^ 



II. Tongue long or short, but its apex acute. The labial 

 palpi normal, or the basal segments sheath-like. Mes- 

 episternal suture rarely present. (Most.) p. 995 . Andrenid^ 



GG. Females and workers with corbiculae (except Psithyrns). 

 First submarginal cell divided by a transverse, hair-like chitinized 

 streak (base of Rs), rarely indistinct. Marginal cell (2d Ri + 

 R2) rather long and pointed or appendiculate, usually as long as 

 the three submarginal cells taken together, and extending far 

 beyond the apex of the third (R4) . Malar space large and distinct. 

 Hind wings stalked, the anal lobe absent. Tongue very long; 

 the two basal segments of the labial palpi and the laciniae elon- 

 gate, and forming a sheath. Social insects with normally a 



worker caste (except in Psithyrus). p. looi Bombid^ 



FF. Hind tibiae without apical spurs. Social insects with a worker 

 caste. Workers with corbiculae; females without functionally de- 

 veloped ones. Marginal cell (2d Ri + R2) long and slender 

 reaching nearly to the wing apex. Anal lobe of the hind wing long 

 and scarcely separated." Cell ist M2 much larger than cell M4. 



Eyes hairy, p. 1005 Apid^ 



AA. Apterous or subapterous (the wings so reduced as to interfere with the 

 normal venation). 



B. The ventral segments membranous, more or less concave with a longi- 

 tudinal fold in dried specimens. 



