18 THE CLASSIFICATION OF INSECTS 



view through all the minor divisions of the whole order. I trust, however, that I 

 have here introduced a sound principle, by means of which the closer relations of 

 the secondary groups of Lepidoptera may be determined. This much can already be 

 said, that the degree of inclination of the wings backwards and downwards, and 

 their greater or less extension sideways, indicate the gradation in which the various 

 types of this order should follow each other. For, when unfolding, the wings of 

 diurnal Lepidoptera, which are at first turned backwards, are next stretched side- 

 ways before they are raised. In accordance with this fact, the Sphinges, which 

 stretch their wings sideways, and in which the upper wings do not fully cover the 

 lower wings, should rank next to the Papilionidse, and be followed by Bombyces, 

 Noctuse, and Geometrse ; and the small Pyralidae, Tortrices, and Tineae, in which the 

 wings are constantly stretched backwards close to the body, which they encircle 

 more or less, should really rank lowest, as they are generally placed in our ento- 

 mological works. 



What I have said of the wings may be applied to the legs and trophi. From 

 careful examination of the caterpillar and pupa, especially during its transforma- 

 tion from the caterpillar state into the pupa state, and from this into that of the 

 perfect insect, the relative perfection of these organs will be as easily ascertained as 

 that of the wings. 



I may add, that the antennae should be examined in their earlier stages with 

 equal attention ; for they are much more uniform in the pupa state, among all fam- 

 ilies of Insects, than in their perfect condition. I have already been very much 

 struck with the fact, that the antennae in the pupa of diurnal Lepidoptera are not 

 yet clavate, as they are in the perfect insect, but resemble rather the antennae of 

 Sphinges, and, in some instances, those of Phalaenae. But my want of knowledge 

 of the special characteristics of Lepidoptera forbids me to enter, at present, into a 

 more extensive and comprehensive comparison. 



IV. REMARKS UPON THE METAMORPHOSES OF SOME DIPTEROUS INSECTS. 



IT is well known that the maggots, which are hatched from the eggs of the 

 meat-fly, and other allied species, undergo no moulting, that is to say, do not 

 cast their skin during their growth, as the larvae of most insects do, but preserve, 

 throughout their larval condition, the same exterior envelope, which, in the full- 

 grown larva, is at last contracted, hardened, and transformed into a case similar to 

 the envelope of the common pupa. 



This analogy has seemed sufficiently strong to induce entomologists to give the 

 name of pupa to that condition of the growing fly ; and simply to distinguish it from 

 an ordinary pupa under the name of pupa coarctata. These pupae are sometimes 

 called cased pupa, because they are cased within the skin of the larva. It is fur- 

 ther known, that after a certain time perfect flies issue from such pupae. It would 

 seem, therefore, that the metamorphoses of the Diptera differ considerably from 

 the metamorphoses of other Insects, and that the perfect insect is directly developed 

 under the skin of the larva, without the transition of the worm into a true pupa. 



