ANATOMY AND PHYSIOLOGY 33 
objects at close range or simply to distinguish between light 
and darkness. 
Sexual Differences in Eyes.—In most Diptera (Fig. 39) 
and in Hymenoptera (Fig. 40) and Ephemeride as well, the 
eyes of the male are larger and closer together (holoptic) than 
Fic. 40. 
Ocelli and compound eyes of the honey bee, Apis mellifera. A, queen; B, drone.— 
After CHESHIRE. 
those of the female (dichoptic). This difference is attributed 
to the fact that the male is morg active than the female, espe- 
cially in the matter of seeking out the opposite sex. Among 
ants of the same species the different forms may differ greatly 
in the number of lateral facets. Thus in Formica pratensis, 
according to Forel, the worker has about 600 facets in each 
eye, the queen 800-900 and the male 1,200. 
Blind Insects.—Many larve, surrounded by an abundance 
of food and living often in darkness, need no eyes and have 
none; this is true of the dipterous “ maggots ’’ and many other 
sedentary larve, particularly such as are internal parasites 
(Tachinide, Ichneumonide), or such as feed within the tis- 
sues of plants (many Buprestidz, Cerambycidee and Curculi- 
onide). Subterranean or cavernicolous insects are either eye- 
less or else their eyes are more or less degenerate, according 
to the amount of light to which they have access. ‘The state- 
ment is made that blind insects never have functional wings. 
Antennz.—The antennz, never more than a single pair 
(though embryonic “ second antenne” occur in Thysanura 
4 
