3$ MECHANICAL FUNCTIONS. 



tigations ! Among the vulgar what eager curiosity, what 

 amazement !" 



96. In the same spirit, Swammerdam, who spent most 

 of his life in making observations on insects, observes on 

 the same subject : " This history is so extraordinary, so 

 amazing in all its circumstances, that it might very well 

 pass lor a romance, were it not built upon the most firm 

 foundations of truth." 



97. With respect to the size and appearance of the cat- 

 erpillars, and of the chrysalids they form, as well as the 

 situations in which they are placed, and the time of re- 

 maining in the torpid state, there are nearly as many 

 varieties as there are species of insects. Some larva:- 

 descend deep into the ground before they assume the 

 torpid state, and there remain three or four years before 

 they acquire wings. Others weave small cocoons, and 

 having thus covered themselves in beds of silk, then 

 change to chrysalids. These are sometimes constructed 

 in the earth, and sometimes attached to the sides of 

 fences, or the side of any vessel in which the worm is 

 confined. If confined in a glass vessel, the observer 

 may witness the whole process of weaving the cocoon, 

 and of casting off the old skin, by which the chrysalis 

 becomes apparent. 



98. The positions in which the larvee place themselves 

 in order to undergo this change, are also extremely vari- 

 ous. One species suspends itself to a leaf with its head 

 downward, being only fixed by the tail ; another passes 

 a rope of silk around its neck, and thus hangs in an ob- 

 lique position ; while others are simply glued in a hori- 

 zontal position, in any convenient place. 



99. Larva which feed on the Parsnip. There is a 

 common larva which may be seen feeding on the leaves of 

 parsnips in the autumn, and which every one has noticed 

 on account of its handsome appearance, and the foetid 

 odor which it emits on being disturbed. The color is 

 greenish yellow, with bands of velvety black, and when 

 full grown it is nearly two inches long. The youngei 

 ones of this caterpillar w r ould at first be taken for a diffei 



What is said of the positions in which chrysalids are placed ? 



