NO. 14 SENSE OBGANS ON MOUTH-PARTS OF BEE — McINDOO 33 



in a single group varies from 40 to 74 ; in a pair of groups, from 82 to 

 134, with an average of 101 hairs for one drone. It is thus seen that 

 each caste possesses virtually the same number of hairs on the 

 epipharynx. 



Variety b. Hairs marked b 1 are found only at the proximal end of 

 the mandible on the outer, dorsal corner (fig. 7, b t ) . There are about 

 85 in each group. 



Hairs marked b 2 occur only on the inner surface of the mandible, on 

 an elevated ridge (figs. 8 and 10, Rg) just posterior to the biting sur- 

 face (BS) . Each mandible has a single row of these organs, consist- 

 ing of about five hairs. 



Hairs marked b 3 are present only on the pharyngeal plate. This 

 plate is a strong chitinous structure forming the anterior part of the 

 floor of the pharynx (fig. 10, PhPl) . It has two terminal points ( figs. 

 9 B and 10, TP) hanging downward over the lower rim of the mouth 

 and two long chitinous rods which are attached to the sides of the 

 plate. These rods (PhPIR) run around the sides and to the top of the 

 pharynx (Ph) , where they are fastened to muscles which in turn are 

 attached to the chitin on the top of the head. The posterior part of the 

 pharyngeal plate is arched upward, forming two large domes, with 

 a deep groove between the domes. The hairs under discussion are 

 grouped on these domes. Some of the hairs point forward, some 

 backward and others toward the roof of the pharynx. The number 

 of hairs in the groups varies only slightly. As an average for workers, 

 there are 90 hairs on a pharyngeal plate ; for queens, 74 hairs ; and for 

 drones, 66 hairs. It is thus seen that these hairs in the three castes 

 vary considerably in number. 



Hairs marked & 4 (fig. 7) are found only on the outer surfaces of 

 the mandibles at the tips. They are arranged irregularly, except that 

 one row follows the contour of the biting edge. The hairs in this row 

 project slightly beyond this edge and often curve over it. There 

 are probably 100 of these hairs on each mandible. 



Variety c. Hairs marked c x are present on the flagella of the 

 antennae where there are no pore plates. Those marked c 2 are usually 

 found between the pore plates. Those marked c 3 occur only on the 

 scapes of antennae. 



Only a few hairs marked c i (figs. 7 and 8) occur on each maxilla. 

 Twenty-five marked c 5 are found on the base of each maxillary palpus. 

 Only a few marked c 6 are present among the olfactory pores on the 

 inner surface of the labial palpus. About 75 marked c- occur on each 

 mandible, the most of them being on the outer surface, and about 40 



