246 AN INTRODUCTION TO ZOOLOGY 



resembling somewhat the ommatidia. An optic nerve from the 

 brain passes to each ocellus. 



VISION. A number of interesting biological problems are 

 directly concerned with the vision of the honeybee and other 

 insects; among these may be mentioned the origin of flowers and 

 cross-pollination, the method of rinding the way back to the 

 hive, and the finding of the queen by the drone during the nuptial 



FIG. 138. Longitudinal section through part of an antenna of the honey- 

 bee, c, conoid hairs; /, tactile hairs; ho., auditory pits; n, nerves; 

 s, smell hollows. (From Cheshire.) 



flight. These questions cannot be definitely answered because 

 the exact character of the image produced by the eyes is not 

 known. A modification of the " mosaic " theory, proposed by 

 Miiller in 1826 and described for the compound eye of the cray- 

 fish on page 207, is still held by many investigators. Movements 

 are made known to the bee very quickly, according to this theory, 

 and the form of objects while the insect is moving are likewise 

 instantly perceived, since the various facets would be affected 

 in succession. 



There is experimental evidence that the ocelli enable the 

 insect to distinguish light from darkness. If images are formed 

 by them, they must be of objects at a definite range, since the 

 lens is incapable of accommodation. Furthermore, the great 

 convexity of the lens makes it probable that form can be perceived 



