INSECTS
ing its development (Figs. 12, 13), and other examples of a metamorphosis during the larval life might be given from the other groups of insects. A larval metamorphosis of this kind is known as hypermetamorphosis, and it shows that the larva may be structurally diversified during its growth to adapt it to several different environments or ways of obtaining its food.
The reader was given fair warning that the subject of insect metamorphosis would become difficult to follow, and even now, with its realization, the writer can not assure him that the above analysis is by any means complete or final. Much more might be said for which there is no space here, and it is not likely that all entomologists will accept all that has been said without a discussion, and possibly some dissension. However, we have not yet reached the end, for we have so far been dealing only with the phase of metamorphosis that has produced the nymph or the larva, and have only briefly touched upon the reverse process which reconverts the creature into the adult.
The pupa unquestionably bas the aspect of an immature adult. It has lost all the characteristic features of the larva, and its organs are those of the adult in the making. It has external wing pads, legs, antennae, compound eyes. Its mouth parts are usually in a stage of development intermediate between those of the larva and those of the adult. Most of the pupal organs are useless, since they are neither those of the larva nor entirely those of the adult, and are not adapted to any special use the pupa might make of them, except in a very few cases. The pupa is, therefore, a helpless creature, unable to eat, or to make any movement except by motions of the body. It is usually said to be a "resting" stage, but its rest is an enforced immobility, and some species attest their impatience by an almost continuous squirming, twisting, or wriggling of the movable parts of the body.
It is evident that it must be an advantage to the pupa
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