32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



into the hairs through which the cellular secretion passes to form 

 the hairs. At first sight these cells resemble sense cells, but a further 

 study shows that they are quite different. The tracheae (Tr) are 

 suspended to the hypodermis by connective tissue (ConT) and the 

 nerves (N) are suspended to the tracheae in the same manner. All 

 the space not occupied by the enumerated structures may be called 

 blood sinuses (BISin). 



A still better idea of how well the mandibles are innervated is 

 gained by referring to figure 6 B. This is a transverse-longitudinal 

 diagram showing the main nerve (N) sending off branches to the 

 sense cells (SC) belonging to the olfactory pores (Por) and the three 

 varieties of innervated hairs (b lt b± and c 7 ). 



3. Disposition of the Innervated Hairs 



In the preceding pages the distribution and number of the sense 

 organs on the mouth-parts have been briefly discussed in connection 

 with their anatomy. Now since we have classified these organs on 

 the basis of their structure, their disposition will be given in detail. 

 In counting the number of sense organs herein discussed, five individ- 

 uals each of workers, queens and drones have been used. Owing to 

 some of the parts being mutilated and concealed, a few of the groups 

 of hairs and olfactory pores could not be counted ; so it was necessary 

 to estimate the number in such groups. It was not possible to count 

 all the sense organs on the mandibles on account of the opaqueness 

 and rotundity of these appendages ; therefore, only estimates of all 

 the sense organs on the mandibles except variety b x of the hairs will 

 be given. 



(a) spinelike hairs 



Variety a. This variety is found only on the epipharynx. The 

 epipharynx is a large three-lobed appendage (fig. 9 A, Ep) depending 

 from the roof of the preoral cavity (fig. 10, Ep) just in front of the 

 mouth (Mo). It is movable up and down and serves to close the 

 mouth opening. These hairs (fig. 9 A, a) are arranged in two groups 

 at the base of the epipharynx, a group lying on either side of the high, 

 vertical, keel-shaped median lobe (K) of the so-called dorsal tongue. 

 For workers, the number of hairs in a single group varies from 41 

 to 79 ; in a pair of groups, from 83 to 147, with an average of 104 hairs 

 for one worker. For queens, the number of hairs in a single group 

 varies from 24 to 92 ; in a pair of groups, from 55 to 176, with an 

 average of 103 hairs for one queen. For drones, the number of hairs 



