24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



The chitin (Ch) at this place is extremely thick, causing the sense 

 fibers (SF) to be very long. In all sections passing through this 

 group of hairs the sense cells (SC) are discernible, but their fibers 

 are usually severed because an entire cell rarely lies in the same plane 

 in which the section was cut. In the 20-day-old pupa the hypodermis 

 (Hyp) is comparatively thin. 



On the ventral side of the mandible (fig. 8, b 2 ) these hairs are 

 straight, but have the same structure as the ones just described, 

 except that the sockets (fig. I C) are sunk only slightly beneath the 

 outer surface of the chitin. 



Those on the pharyngeal plate (fig. 1 D, b 3 ) are slightly larger than 

 the ones just described. These are slightly curved and most of them 

 point toward the mouth. Their sockets stand a little above the level 

 of the chitin, and the walls at their tips are not so thick as at the 

 bases. The sense fibers run nearly all the way to the tips of the hairs. 

 Beneath the pharyngeal plate in the 21 -day-old pupse, the hypodermis 

 (Hyp) is extremely thick and its cells are so grouped together that 

 each hair seems to be innervated by a large group of cells, but in all 

 such cases no sense fibers were seen running from the groups to the 

 hairs. After spending considerable time it was ascertained that the 

 sense cells (SC) seldom lie in the middle of the hypodermis, but near 

 its inner edge. They are usually cut transversely, and for this reason 

 the fibers are rarely seen connecting with the cell bodies. 



The hairs (figs. 1 E and 7, & 4 ) at the distal ends of the mandibles 

 are the longest ones of this variety, and their tips are blunt, while 

 the tips of the others are sharp. In structure they are like those on 

 the ventral side of the mandibles (fig. 1 C, b 2 ), except that they are 

 slightly curved. 



Variety c. This variety, found on the head and all the head appen- 

 dages, varies from the smallest hairs on the antennae (fig. 2 A) to the 

 largest on the maxillae (fig. 2 U). Figure 2 A and B represent the 

 smallest and largest on the flagellum of a worker bee, and figure 2 C 

 those on the scape. All of those on the maxillae are of about the same 

 size (fig. 2 D and E), but when first observed those on the maxillary 

 palpi (fig. 2 E) appear to be the smallest. Those on the labial palpi 

 (fig. 2 F) are slightly larger than those on the maxillae. Those on the 

 mandibles (fig. 2 G) and paraglossae (fig. 2 H) are of the same 

 size and are considerably larger than the ones just described. On the 

 cervical plate (fig. 10, CvPl) these hairs (fig. 2 I to K) vary con- 

 siderably in size. Just inside the buccal cavity a few innervated hairs 

 (fig. 2 L) were found; also a few (fig. 2 M) on the head near the 



