THE HEAD OF THE BEE AND ITS APPENDAGES. 37 



insertions which are connected with the ends of nerve fibers. Some 

 of them stand expbsed on the surface of the cuticle while others 

 are sunken into, or entirely concealed within, pits of the integument. 

 In addition to these, there are two other kinds of special hairs on 

 the antennae which have no nerve connections, while, finally, the ordi- 

 nary hairs, such as are found on all parts of the body, occur also on 

 them, especially on the scape. 



The special hairs not provided with nerve endings are of two 

 sorts. One is a solid curved or hooked hair (fig. 12 A, Hr) which 

 is simply articulated into a socket of the cuticle {Gtl), while the 

 other (B) is hollow and is situated over a channel through the cuticle, 

 and contains a prolongation of a specially enlarged epithelial cell 

 {Gl) lying beneath it. These hairs can not be regarded as sensory, 

 since they have no communication with the central nervous system, 

 and it is not clear just what purpose they do serve. 



The simplest sensory organ is a short, hollow, conical hair (C, 

 Hr) arising directly from the surface of the cuticle, over a wide 

 oprning through the latter, and containing the end of a sensory cell 

 {CI) connected with a nerve fiber {Nv), which goes into the main 

 trunk of the axial antennal nerve. A modified form of this organ 

 consists of a curved hair (D, Hr) set into a small depression over 

 the cuticular channel. Such hairs are probably tactile in function; 

 that is to say, by means of them the bee can perceive that its antennae 

 are in contact with some surface. The general integument is too 

 thick and dense to allow of any sort of delicate touch sensation being 

 communicated through it, but if one of these movable hairs brushes 

 against an object the nerve within it must be at once stimulated. 

 Tactile or touch hairs are distributed especially over the outer sur- 

 face of the antenna* and at its apex, but occur also scattered over 

 the other parts of the body and on the mouth parts. 



Microscopic sections of the antennae reveal still other organs 

 which are not so apparent on the surface as the hairs just described. 

 One of these is shown at E of figure 12. It consists of a small pit 

 {Pt) in the integument, widened basally, and having a small papilla 

 on its floor, in whose summit is the opening of a still deeper cavity 

 which also expands toward its deeper end. This inner cavity is 

 almost filled up by a conical plug {H7') which arises from its floor 

 and ends just below the aperture into the outer pit. The plug con- 

 tains a thick nerve ending which arises from a ganglion cell con- 

 nected with the antennal nerve by a nerve' fiber. Ten or more of 

 these sense organs occur on the terminal and the first three segments 

 of the flagellum. It is evident that each is simply a sensory hair 

 which has been doubly sunken into a cavity of the integument. 



