IN SECT A. 329 



That of the chrysalides of the Lepidoptera merely consisting of a 

 simple pellicle applied to the external organs, following their contour 

 in every direction, and forming, for each of them, so many moulds, like 

 the envelope of a mummy, allows us to recognise and distinguish them ; 

 but those of Flies and Syrphi, formed of the dried skin of the larva, 

 resemble an egg-like shell. It is a species of capsule or case in which 

 the animal is shut up. 



Many larvae, before they pass into their pupa state, prepare a cocoon 

 in which they enclose themselves, either with silk which they draw 

 from the interior of their bodies by means of the spinning apparatus of 

 their lip, or other materials which they collect. The perfect Insect 

 issues from the nymph through a fissure or slit which opens on the 

 back of the thorax. In the pupae of Flies one of the extremities is 

 detached, like a cap, to allow the egress of the animal. 



The larvae and pupae of those Insects which experience a semi-meta- 

 morphosis only differ from the same in a perfect state, in the absence 

 of wings. The other external organs are precisely alike. But in such 

 as undergo a complete metamorphosis, the form of the body of the larva 

 has no constant relation with that it is to possess in its perfect state. 

 It is usually more elongated ; the head is frequently very different, as 

 well in its consistence as in its figure, having mere rudiments of 

 antennae or perhaps none at all ; there are never any compound eyes. 



There is also a great disparity in the organs of manducation, as may 

 be easily seen by comparing the mouth of a Caterpillar with that of the 

 Butterfly, or the mouth of the larva of a Fly with that of the perfect 

 Insect. 



Several of these larvae are destitute of feet ; others, such as the 

 Caterpillars, have many, all, the six first excepted, membranous, and 

 without terminal hooks. Some Insects, such as the Ephemerae, exhibit 

 a singular anomaly in their metamorphosis the animal arrived at its 

 perfect state undergoes another change of tegument. 



The Insects which constitute our three first orders preserve for life 

 their natal form. The Myriapoda, however, exhibit a kind of meta- 

 morphosis. At first they have but six legs, or, according to Savi, are 

 altogether destitute of them ; the others, as well as the segments on 

 which they depend, are developed by age. 



But few vegetable substances are protected from the voracity of 

 Insects ; and as those which are necessary or useful to man are not 

 spared by them more than others, they become very injurious, particu- 

 larly during seasons which favour their multiplication. Their destruc- 



