Figs. 67, Head of male— 6S, Ditto of female 

 Syrphus. 



OCELLI. 237 



them upon the top of the head (figs. %"] and 68). The same 

 also occurs in the male hive-bee, and a few others. 



In some insects, however, 

 the eye appears to be com- 

 pletely wanting. This is 

 asserted to be the case in 

 the remarkable parasitic in- 

 sect, thence named Braula 

 cceca, in the genus of bee- 

 tles, Clinidium, Kirby ; and 

 in the ants forming the 

 genus P oner a. In like man- 

 ner I have been unable to 

 observe the least trace of eyes in more than one exotic 

 species of ant ; and in some of the Centipedes the same is 

 stated to be the case. 



[b) The Ocelli or Simple Eyes (o in the figures). 

 These organs (sometimes also named /S^emmcffa) are minute, 

 nearly globular lenses, placed upon the cro^^^l of the head 

 or the forehead, between the upper region of the eyes. Un- 

 like the composite eyes, they are often entirely wanting, and 

 are never present in the imago unless as accompaniments to 

 the latter. In their organization they appear to be similar 

 to the lateral point-like eyes of caterpillars or the eyes of 

 spiders. In general they are three in number, placed in a 

 triangle, or more rarely almost in a line. Occasionally, 

 however, there are but a pair of these ocelli, as in many lepi- 

 dopterous insects, where they are present, although concealed 

 by hairs, in the mole-cricket, in many bugs and smaller frog- 

 hoppers ( Cercopidce) ; in some of the sand- wasps {Larra, 

 &c.) the hinder pair are almost obsolete ; and in some of 

 the coleopterous insects, belonging to the family Dermestidw, 

 there appears to be but a single ocellus. They appear in the 

 ants to be connected with the developement of the sexual 



