l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, IO3 



the stipes (fig. 4E), its broad outer part being vertical and the 

 narrower mesal part horizontal, as the two galeae overlap to form the 

 roof and the sides of the temporary proboscis canal (figs. 3 C, 9 C). 

 When the proboscis is retracted the galea is bent back and folded 

 upside down below or behind the stipes (fig. 3D). 



The folding of the galea is produced by a single muscle arising in 

 the stipes (fig. 4 F, 75), which evidently represents the usual galeal 

 flexor of other insects. The action of the muscle in the bee, however, 

 depends on a special device in the base of the galea. Where the galea 

 joins the subgalea it is abruptly narrowed, and the lateral margin of 

 the narrow part is thickened to form a small leverlike ridge (E, g) 

 that articulates proximally on the tapering, laterally curved end (/) 

 of a long narrow sclerite (^) in the mesal wall of the stipes. On the 

 middle of the lever ridge is attached the tendon of the flexor muscle 

 of the galea (F, 15). The tension of the muscle in contraction first 

 depresses the galea and turns it backward and outward because of 

 the obliquity of the line of bending (E, a-h) between the galea and 

 the subgalea; but a second line of bending {c-d) beyond the first and 

 oblique in the opposite direction soon counteracts the lateral move- 

 ment, so that the continuing pull of the muscle finally turns the galea 

 straight back and folds it up against the stipes. The extension of 

 the galea evidently results automatically from the elasticity of its base 

 and its basal continuity with the firmly affixed subgalea (G). 



The large, soft, cushionlike lobe of the stipes that arises at the 

 mesal side of the subgalea (fig. 4 A, D, F, G, Id) is a prominent 

 feature of the bee's maxilla. On its proximal end is a small sub- 

 sidiary lobe (D, G, Lc) bearing a few small setae, which, by com- 

 parison with other Hymenoptera (fig. 5), evidently represents the 

 maxillary lacinia. In a vespoid wasp (fig. 5A, B) the lacinia is a 

 well-developed lobe {Lc) arising from the stipes mesad of the base 

 of the larger galea {Ga). In Bomhus (D) and Xylocopa (E) the 

 lacinia is a small setigerous or spiny lobe overlapping a large mem- 

 branous area of the stipes. It would appear, therefore, that the major 

 part of the large cushionlike lobe of the maxilla in Apis (fig. 4 D, Id) 

 is a development of the sublacinial membranous area present in 

 Bo'tnbus and Xylocopa, and that the small setigerous lobule {Lc) 

 on its base is a remnant of the lacinia proper. The entire structure in 

 Apis is here termed the lacinial lobe; it plays an important part in the 

 closure of the food channel on the base of the proboscis. 



In the steeply declivous proximal wall of the lacinial lobe is a 

 small curved sclerite (fig. 4 E, Ivr) with a tapering distal arm and a 

 thickened base, which latter is connected by a fulcral point with the 



