242 LECTURE XVIII. 



worm in their habits, and continue for three years burrowing in the 

 soil and devouring the roots of grass and other vegetables. The larva 

 of the stag-beetle bores its way into the trunk of a tree, generally a 

 willow or oak, and remains there six years. It is furnished with two 

 powerful jaws, with which it gnaws the Avood. It forms a cocoon of 

 the minute chips or tan, to which it reduces the wood, and passes a 

 considerable period in the jnipa state ; during which, the large horns 

 of the male are folded upon the breast and abdomen, protecting the 

 antennse and legs. 



The anatomy of an insect in its different stages of development, and 

 the changes of both the external and internal parts in the progress 

 from the larva to the imago state, have been most accurately 

 and closely examined in Lepidopterous insects. Many of these 

 changes are shown by Hunter, in his extensive series of prepara- 

 tions of the silkworm moth.* They were investigated by Lyonnet 

 in the Cossus Ugniperda. They have been described and illustrated 

 with much accuracy and detail by Herold in the Papilio JBrassiccB, 

 and by Mr. Newport in the Sphinx Ligustri. The larvae of the Le- 

 pidoptera quit the egg with a scaly head and jaws, with three pairs 

 of thoracic legs, short, and with claws (^Jig. lO^, o,p,q), and usually 



104 



Sphinx Ligustri. Larva. 



n 



four pairs of tubercular prolegs (r, r), supported by the sixth, seventh, 

 eighth, and ninth segments ; sometimes there is also a fifth pair 

 upon the anal segment. The prolegs, which entirely disappear in the 

 pupa, are however less constant than the thoracic legs. The larvce 

 of the lepidoptera are commonly herbivorous, and devour considerable 

 quantities of vegetable matter. The coarsely masticated leaves are 

 conveyed by a short and wide cesophagus (^Jig. 104. f/), to a much 

 longer and Avider chylific stomach (Jt). Six pairs of capillary bile- 

 tubes (/) indicate by their insertion the commencement of the intestine 

 (?w), which terminates by a wide, short, and longitudinally plicated 

 rectum at n, upon the last segment. 



In its perfect state, the butterfly, or sphinx, subsists only on 

 the fluids of vegetables : its maxillary apparatus is converted by the 

 abrogation of the horny mandibles and the extreme prolongation of 

 the maxillee, into the antlia (^fg. 105. i), already described. A 



* See Nos. 297 G. to 303G. inclusive. 



