l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



mistakenly, is attached "near" the base of the palpus. There can be 

 no question that the muscle is inserted directly on the base of the 

 palpus (fig. 4 B), and it is not clear how it could act as an extensor 

 of the galea. Duncan (1939) says there are two muscles for each 

 maxillary palpus in Vespula inserted on the palpal base. 



The labium and hypopharynx. — The labium of the bee presents 

 externally all the parts of a generalized labial appendage (fig. 3 A). 

 The lengthened base contains a small, triangular postmental sclerite 

 (Pint) and a long trough-shaped premental plate (Prmt). Diverging 

 from the end of the prementum are the slender, four-segmented 

 labial palpi (LbPlp), each supported on a small basar stalk, and 

 between the latter arise the ligular lobes, including the long, median, 

 so-called tongue (Gls), which is probably the combined glossae, and 

 a pair of short lateral paraglossae (Pgl). The postmentum and the 

 proximal part of the prementum are suspended in the membranous 

 floor of the fossa of the proboscis (PF) on the back of the head, 

 and are membranously united also with the bases of the maxillary 

 stipites. The apex of the postmentum is embraced by the angle of 

 the lorum (Lr), and turns in the latter when the proboscis is pro- 

 tracted or retracted. In the completely retracted position the apex 

 of the lorum rests in the depression of the hypostomal bridge (HB). 



The premental sclerite covers only the posterior and lateral walls 

 of the premental area of the labium, the anterior wall being entirely 

 membranous (fig. 6 A, 7 D). The membranous anterior wall ends in 

 a transverse inflection at the bases of the ligular lobes (fig. 6 A), and 

 in this groove, as may be seen by separating the paraglossae (B), is 

 the opening of the salivary ejection apparatus (SIO). The apparent 

 anterior wall of the prementum, therefore, represents the hypopharynx 

 (B, Hphy) adnate upon the labium, since the salivary duct in 

 generalized insects opens between the hypopharynx and the labium. 

 The hypopharyngeal surface in the bee, furthermore, extends up 

 to the functional mouth (fig. 10 A, Hphy), and includes the oral 

 plate {opl) on the floor of the mouth cavity at the entrance to the 

 sucking pump and the biblike fold {bib) that hangs down from the 

 margin of the plate. The ascendent hypopharyngeal surface is flanked 

 by a pair of slender suspensorial rods (figs. 7 D, 9 A, s) that extend 

 from the base of the prementum to the mouth angles, and probably 

 represent lateral hypopharyngeal sclerites of generalized insects. 



The ligular lobes of the labium have a common base which is con- 

 tinuous with the prementum (fig. 6 A, B, C), but is supported on the 

 latter anteriorly by a pair of ligtdar arms (A, B, h), and posteriorly 

 by a triangular subligular plate (C, k). The ligular arms are sclerotic 

 bands arising from the anterior margins of the premental plate; at 



