NO. 14 SENSE ORGANS ON MOUTH-PARTS OF BEE — McINDOO 45 



elucidated by the fact that the paraglossae, in closing- tightly around 

 the base of the tongue, make a perfect tube which connects the groove 

 on the ventral side of the glossa with the one on the dorsal side of the 

 same appendage, and perhaps most of the liquid food is sucked into the 

 mouth from the cavity formed by the paraglossce. 



We are now ready to explain how the liquid is sucked into the mouth. 

 Cross-sections through the head of the bee show that the pharynx 

 (fig. 10, Ph) assumes various shapes, but the shape shown in figure 

 10 is the most typical. Just posterior to the hairs (6 3 ) on the pharyn- 

 geal plate, it expands into a large, saclike body, while its posterior end 

 gradually becomes smaller and is called the oesophagus (£) where it 

 enters the thorax. The walls of the alimentary tract, from the mouth 

 to the honey stomach, were examined to see if they contain sense 

 organs, but none was found other than those already described. 

 Nerves running to the cervical plate (iV 6 ), pharyngeal plate (A^) and 

 the epipharynx (A/" 4 ) were seen, but no other nerves were observed 

 connected with the pharynx, although several muscles were traced 

 from the pharynx to their places of attachment. A study of these 

 muscles shows that the pharynx may be moved in at least six different 

 ways as follows: Muscles marked M 4 pull it forward; M 5 , upward; 

 M 6 and M 7 , upward and backward ; M 8 , directly backward ; M Q , down- 

 ward and backward ; and M 10 and I n change the diameter of it. 

 It will be seen that M 7 is attached to the pharyngeal plate rod 

 (PhPIR) and M 8 is fastened to the pharyngeal plate. The contrac- 

 tion of either one of these muscles would enlarge the tube leading 

 from the mouth to the pharynx. From the preceding description 

 it is easily understood that by various combinations of these muscles 

 the pharynx works like a powerful pump, and when the liquid food 

 on the dorsal surface of the mentum is raised to the mouth opening, 

 the suction from the pharynx draws it into the mouth as easily as 

 a person draws into his mouth water held in the palm of the hand. 



7. Summary of Sense Organs 



Only two general types of sense organs were found on the mouth- 

 parts of the honey bee. They are innervated hairs and innervated 

 pores, called olfactory pores by the writer (1914a). Judging from 

 their anatomy, the innervated hairs can serve only as tactile organs, 

 and none of them are anatomically adapted to function either as 

 olfactory organs or as gustatory organs. The writer has divided them 

 into spinelike and peglike hairs. Both types vary considerably in 

 size and structure. In size the spinelike hairs vary from the smallest 



