30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



seems absolutely necessary for the following reason. In adult bees the 

 hypodermis is quite thin and in certain places has practically disap- 

 peared. It no longer is firmly fastened to the chitin and it can no 

 longer hold the sense cells in their proper places. If the sense fibers 

 were fastened to the chitin only by the ends of their walls and not by 

 the entire peripheral ends being surrounded by the chitinous cones, 

 the sense fibers would break loose from the pore apertures. Firm 

 attachments for the sense fibers in spiders (Mclndoo, 191 1) are not 

 necessary, because the sense cells lie in a thick hypodermis which per- 

 sists throughout the lives of the spiders ; and furthermore, cones are 

 not formed, because the pore apertures pass entirely through the 

 cuticula, so that the sense fibers join the apertures on the internal 

 surface of the integument. 



The olfactory pores on the base of the tongue (fig. 5 B), maxillae 

 (fig. 5 C), labial palpi (fig. 5 D),and the smallest on the mandibles, are 

 of about the same size as those on the wings. The spindle-shaped 

 sense cells are easily seen ; but owing to the small size of the pores, the 

 pore apertures are rarely discernible. Beneath the group of pores 

 on the labial palpus, the sense cells (fig. 5 D, SC) occupy about a half 

 of the space in the appendage. Fig. 5 E and F represent, respectively, 

 the sizes of the pores found on the side of the head near the base of 

 the mandible, and just inside the buccal cavity. A nerve (N 2 ) and 

 a trachea (fig. 2 F, Tr) run near the group of sense cells through the 

 labial palpus. Figure 2 I shows the structure of the largest olfactory 

 pores on the cervical plate. These are equally as large as the largest 

 ones on the mandibles, but the smallest ones are never so small as the 

 smallest on the mandibles. 



Under the microscope with transmitted light the olfactory pores 

 appear as bright spots. Each bright spot is surrounded by a dark 

 line, the pore wall (fig. 5 G, PorW). Outside this line the chitin is 

 generally dark in color, while inside of it the chitin is almost trans- 

 parent, and at the center there is an opening, the pore aperture 

 (PorAp). 



Figure 5 G to K represent, respectively, the sizes of the superficial 

 appearances of the pores on the mandible, tongue, maxilla, labial 

 palpus, and cervical plate. 



To learn how well the mandibles are provided with sense organs, 

 the reader is referred to figure 6 A. This is a semidiagrammatic 

 drawing taken from one cross-section through the middle of a man- 

 dible of a 20-day-old worker pupa. The details of the hypodermis 



