1606 EN TOMOLOGY 
developed sense organs, excellent powers of locomotion, spe- 
cial protective and aggressive devices, etc. In insects as a 
whole, the environment of the larva or nymph and that of the 
adult are very’ different, as in the dragon fly or the butterfly, 
and the larvee are modified in a thousand ways for their own 
immediate advantage, without any direct reference to the 
needs of the imago. 
The chief purpose, so to speak, of the larva is to feed and 
grow, and the largest modifications of the larva depend upon 
nutrition. Take as one extreme, the legless, headless, fleshy 
and sluggish maggot, embedded in an abundance of food, and 
as the other extreme the active and “ wide-awake”’ larva of 
a carabid beetle, dependent for food upon its own powers of 
sensation, locomotion, prehension, ete., and obliged meanwhile 
to protect or defend itself. Between these extremes come 
such forms as caterpillars, active to a moderate degree. The 
great majority of larval characters, indeed, are correlated with 
food habits, directly or indirectly; directly in the case of the 
mouth parts, sensory and locomotor organs, and special struc- 
tures for obtaining special food; indirectly, as in respiratory 
adaptations and protective structures, these latter being numer- 
ous and varied. 
Larvee that live in concealment, as those that burrow in the 
ground or in plants, have few if any special protective struc- 
tures; active larve, as those of Carabidze, have an armor-like 
integument, but owe their protection from enemies chiefly to 
their powers of locomotion and their aversion to hght (nega- 
tive phototropism) ; various aquatic nymphs (Zaitha, Odonata ) 
are often coated with mud and therefore difficult to distin- 
guish so long as they do not move; caddis worms are con- 
cealed in their cases, and caterpillars are often sheltered in a 
leafy nest. There is no reason to suppose that insects conceal 
themselves consciously, however, and one is not warranted in 
speaking of an instinct for concealment in the case of insects— 
since everything goes to show that the propensity to hide, 
though advantageous indeed, is simply a reflex, inevitable, 
