28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



slightly curved, and have blunt tips (fig. 4 E) . The chitin of the distal 

 half of the maxilla contains many long longitudinal and deep grooves 

 (fig. 4 E, Gv). These grooves cause the wide maxillary lobe to be 

 quite flexible, thus enabling the bee to fold the maxillae around the 

 other mouth-parts. 



Judging from the anatomy of all the spinelike and peglike hairs 

 described in the preceding pages, it does not seem possible that they 

 can serve either as gustatory or as olfactory organs because the 

 odoriferous particles in the air and the liquids carrying substances in 

 solution could not pass through the hard and thick walls of the hairs 

 to stimulate the ends of the nerves. Since insects cannot feel weak 

 mechanical stimuli through their chitinous integuments without some 

 kind of a sensory organ, it seems that all of these innervated hairs are 

 well adapted to serve as tactile organs. The sense of touch is further 

 discussed on page 39. 



2. Structure of the Olfactory Pores 



Olfactory pores were found on the mandibles (figs. 7 and 8, Md, 

 For), maxilla? (fig. 8, Mx), labial palpi (fig. 7, LbPlp), tongue (fig. 

 7, Gls) , side of head, in the buccal cavity, on the cervical plate and on 

 the bases of the scapes of the antennae. In structure all of these are 

 similar, and they are identical with those which have already been 

 found on the legs, wings and sting. 



Figure 5 A represents one of the largest olfactory pores found on 

 the mandibles. The chitin (Ch) of the mandibles is always very 

 thick, making the necks (fig. 5 E, NkFl) of the small pores long and 

 slender. A chitinous cone (fig. 5 A, Con) is always present. In 

 pupae these cones are usually connected with a hypodermal secretion 

 (HypS), but in adults this secretion is never seen. Sometimes this 

 secretion fills the entire pore, and it generally contains streaks run- 

 ning from the hypodermis (Hyp) to the cone. Unless all stages 

 of these organs are critically studied, it is easy to imagine that 

 this secretion is a permanent structure of the pores. This ex- 

 plains why Janet (1911) regards this substance as a part of the 

 organ, and why he thinks that the cavity of the pore is filled with 

 two or three concentric cylinders. In studying the same organs 

 in Coleoptera, the writer (1915, p. 422) shows that the cones are a 

 later formation than the chitin surrounding them and that the hypo- 

 dermal secretion does not begin to form the cones until the sense fibers 

 have connected with the pore apertures. The writer has also shown 



