IN SECT A. 479 



All insects do not pass through these three states. Those wlilch have no wings 

 come fortli from the egg with the forms they are always to maintain, — the Flea, female 

 MutilliE, Worker Ants, and a few others, excepted. These are called insects without 

 a metamorphosis. Among those which have wings, a great number undergo no other 

 change than that of acquiring them. These are said to undergo a demi-metamorphosis, 

 their larva resembling the perfect insect, with the exception of the wings, which are 

 entirely wanting. The pupa differs only from the lan'a in having rudiments of wings, 

 which are developed at the last moulting, which brings the insect to the perfect state. 

 Such are the Cimices, Grasshoppers, &c. Finally, the other insects provided with 

 wings are said to undergo a complete metamorphosis, appearing, at first, under the 

 form of a caterpillar or worm, and subsequently becoming an inactive nymph, but 

 wdiich exhibits all the parts of the perfect insect contracted, and, as it were, enveloped 

 in a bandage. 



I'hese parts are free, although very closely approximated and ajiplied against the 

 body, in the pupre of the Coleoptera, Neuroptera, Hymenoptera, &c. ; but this is not 

 the case in those of the Lepidoptera, and many of the Diptera. An elastic or still more 

 solid skin is moulded over the body, and its exterior parts form for it a kind of case. 

 The skin of the chrysalides of Lepidoptera, consisting only of a simple pellicle applied 

 upon the external organs, following all their directions, and forming for each of them 

 so many moulds, like the envelope of a mummjr, permits them to be recognized and 

 distinguished [pi/pa obtecta, Linn.] ; but that of the two-winged flies, being formed of 

 the dried skin of the larva, has merely the appearance of a cocoon in the shape of an egg. 

 It is a kind of capsule, or case, in which the animal is inclosed {pupa coarctata, Linn.) 



Many larv», previous to passing to the pupa state, construct for themselves, with 

 silk which they draw from the interior of their own bodies, by means of the spinnerets 

 of their lower lip, or with other materials which they have collected, a cocoon, in which 

 they are inclosed. The perfect insect comes forth from the pupa by a slit or fissure 

 which it makes down the back of the thorax. In the pupa of two-winged flies, one of 

 its extremities is detached, in the form of a cap, for the passage of the insect. 



The larva? and pupa of the insects with a semi- metamorphosis, differ only from the 

 perfect state of the same insects in respect to their wings. The other outer organs are 

 identical. But in complete metamorphosis, the form of the body of the larva does not 

 alwajrs bear a constant relation with that which these insects have in their final state. 

 It is generally more elongated ; the head is often very different, both in its consistence 

 and figure, and has only the rudiments of antenna;, or else wants them absolutely, and 

 never exhibits composite eyes. The organs of the mouth are also ver}' different, as may 

 be at once perceived by comparing the mouth of a Caterpillar with that of a Butterfly, 

 or the mouth of the larva of a Fly with that of the same insect perfectly developed. 

 Many of these larvK have no feet ; others, such as those of Caterpillars, have many ; 

 but these, with the exception of the six anterior, are entirely membranous, without 

 hooks at the tip. Some insects, such as the Ephemera?, exhibit a singular exception in 

 the metamorphosis : arrived at their perfect state, they again cast ofi^ another skin 

 from their wings. 



The insects which compose our first three orders, preserve, throughout life, the form 

 which they have when born. The Myriapoda, however, exhibit the rudiments of meta- 

 morphosis, having at first only six feet, or being even, according to Savigny, entirely 



