3t52 MOTIONS OF INSECTS. 



described to you the grates which shut up their cases? 

 when they became quiescent^; if they had no means 

 of piercing- these grates, they would perish in the wa- 

 ters. The head of these pups is provided at first with 

 a particular instrument, which enables them to effect 

 this purpose. The anterior part of the head is armed 

 with a pair of hooks in form resembling the beak of a 

 bird; and with this, previously to their last change, 

 they make an opening in the grate which, though it 

 once defended, now confines them. But at this moment, 

 perhaps, the insect has a considerable space of water 

 to rise throuffh before she can reach the surface. This 

 is all wisely provided for ; before she leaves the en- 

 velope which covers her body, she emerges from the 

 water, and fixes herself upon some plant or other ob- 

 ject, the summit of which is not overflowed. But you 

 will here, perhaps, ask — How can a pupa in her enve- 

 lope, with all her limbs set fast, do this ? This affords 

 another instance of the wise provision of the benefi- 

 cent Father of the universe for the welfare of his crea- 

 tures. The antennae and legs of this tribe of insects, 

 Avhen they are pupa;, are not included, as is the case 

 with most that are quiescent in that state, in the gene- 

 ral envelope ; but eacli in a separate one, so as to al- 

 low it free motion. Thus the insect when the time is 

 come for its last change can use them (except the hind-., 

 legs, which being partly covered by the wing-cases re- 

 main without motion) with ease. It then stretches out 

 its antennae, and steering with its legs makes for the 

 surface. De Gecr saw one just escaped from its case 



* Sec above, p. 26i. 



