THE POPULAR INSECT PLAN 



205 



Experiments in which the antennae were removed, together with 

 evidence from microscopic examinations of the antennae, indicate 

 that they hold many of the sense organs which perceive odors. Small 

 pits, in which these sensory cells are located, are found on the surface 



A.'-- 



-;-simple. eyes 



compcurjct eye 



labrum. 



n^andible. 



maxilla 



maxillary 

 palp 



Simpla eyes 

 Compound.- eye^ 



clypeu? 

 ■labram 



^a-ndiWe 



palp 



ma^cilla 



labium. 

 ..labial palp 



■■prob^ 



oseis- 



labium. 



labial palp 



IT 



Ij.... tongue^ (glossal 

 i*»-labellu.ra X 



L Head of worker, lateral view, mouth part labeled. H. Head of worker, 

 lower view, lower part of proboscis cut away. Compare these mouth parts with 

 those of the locust. Which shows the more primitive condition!' 



of the antennae. The queen has about 1600 of these pits on each 

 antenna, the workers about 2400, and the drones about 37,800. This 

 large number probably makes it possible for the drones to find the 

 queen during her nuptial flight, at which time sperm cells are placed 

 within her body so as to insure fertilization of the eggs as they are laid. 

 The eyes of the bee, as well as those of other insects and crustaceans, 

 are compound. This means that they are composed of individual 

 units called ommatidia. Each onmiatidium consists of the retinula, 

 a group of elongated sensory cells, which encloses a rodlike rhahdom, 

 the latter made up of the sensory edges of the retina] cells. At the 

 outer edge is a corneal lens, under which is formed a crystalline cone. 

 The retinal cells are connected with the optic nerve fibers, the entire 

 apparatus being covered with a layer of i)igment cells, so that each 

 ommatidium is a unit, and according to experimental evidence, is 



