I1i4 EN TOMOLOGY 
pigment cells elongate around the ommatidium and their pig- 
ment granules absorb from the cone cells and rhabdom the 
excess of light. If the light is weak, they shorten, and absorb 
but a minimum amount of light. 
Origin of Compound Eye.—The compound eye is often 
said to represent a group of ocelli, chiefly for the reason that 
externally there appears to be a transition from simple eyes, 
through agglomerate eyes, to the facetted type. This plausi- 
ble view, however, is probably incorrect, for these reasons 
among others. In the ocellus, a single lens serves for all 
the retinulz, while in the compound eye there are as many 
lenses as there are retinule. Moreover, ocelli do not pass 
directly into compound eyes, but disappear, and the latter arise 
independently of the former. 
Probably, as Grenacher holds, both the ocellus and the com- 
pound eye are derived from a common and simpler type of 
ce 99 
are “sisters,” so to speak, derived from the same 
eye 
parentage. 
Perception of Light through the Integument.—In vari- 
ous insects, as also in earthworms, blind chilopods and some 
other animals, light affects the nervous system through the 
general integument. Thus eyeless dipterous larvee avoid the 
light, or, more precisely, they retreat from the rays of shorter 
wave-length (as the blue), but come to rest in the rays of 
longer wave-length (red), as if they were in darkness (see 
page 350). The blind cave-beetles of the genus Anophthal- 
mus react to the hght of a candle (Packard). Graber found 
that a cockroach deprived of its eyesight could still perceive 
light, but Lubbock found that an ant whose eyes had been 
covered with an opaque varnish became indifferent to light. 
Color Sense.—Insects undoubtedly distinguish certain col- 
ors, though their color sense differs in range from our own. 
Thus ants avoid violet light as they do sunlight, but probably 
cannot distinguish red or orange light from darkness; on 
the other hand, they are extremely sensitive to the ultra-violet 
rays, which make no sensible impression upon us. Honey 
