THE HONEYBEE AND BEES IN GENERAL 



245 



ganglion in the thorax sends nerves into the front pair of legs. 

 The posterior thoracic ganglion is comparatively large, consisting 

 really of several ganglia which have grown together. The an- 

 terior part of this ganglion supplies the fore wings and the middle 

 pair of legs; the posterior part innervates the hind wings and 

 legs. Various parts of the abdomen are supplied with nerves 

 from the abdominal ganglia; the last of these is larger than the 

 others, because of the important organs, the genital apparatus 

 and the sting, which are innervated by them. 



The stomato-gastric part of the nervous system is made up of 

 many small ganglia connected with the organs of digestion, cir- 

 culation, and respiration. 



Each segment of the body contains a triangular ganglion from 

 which fine nerve fibers pass to all parts of the body. This is the 

 so-called sympathetic nervous system. 



THE SENSORY ORGANS. THE EYES AND VISION. p:ach 

 compound eye is made up of a great number of long, slender 

 structures called ommatidia. There may be as many as five 

 thousand of these in a single eye. The ommatidia are all alike 

 in structure. They may be recognized externally as minute 

 hexagonal areas or facets, among which arise long protective hairs 

 which are unbranched. Passing from without in, the omma- 

 tidium is found to contain the following parts: the cornea; the 

 crystalline cone composed of four modified cells surrounded by 

 two cells containing coloring matter ; and the rhabdome, a deli- 

 cate transparent rod surrounded by eight slender retinular 

 cells, and about twelve pigment cells, which extend to a basal 

 membrane. In all there are twenty-eight parts to each 

 ommatidium (216). The pigment cells prevent the reflection 

 of light within the ommatidium and between neighboring 

 ommatidia. 



The ocelli, though commonly known as simple eyes, are almost 

 as complex as the compound structures just described. Each 

 ocellus consists of an extremely convex cornea, and a large bi- 

 convex crystalline cone, behind which are a great number of rods 



