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in the caterpillar of this insect are furnished 

 with a kind of lips, which open or close them at 

 pleasure ; and it is probable, by a similar appa- 

 ratus, that all terrestrial insects regulate the in- 

 gress and egress of the air employed in respira- 

 tion. But some terrestrial insects are capable 

 of respiring even under water ; and the means 

 by which they do this is extremely curious. In 

 general they carry down with them a consider- 

 able portion of air in the interstices of the hairs 

 with which their bodies are covered, and which, 

 continually exuding an oily fluid, prevents the 

 water from coming in contact with it : they 

 breathe, therefore, under these circumstances, 

 in a kind of natural diving-bell. In some in- 

 sects, however, as the water-scorpion, the air- 

 tubes instead of this contrivance are provided 

 with long processes extending from the posterior 

 part of the body, the extremities of which being 

 always above the water, furnish them with a 

 constant supply of fresh air. They are, in fact, 

 a kind of water-serpent, or cetaceous animal, in 

 this respect ; the bulk of their bodies being un- 

 der water, while their spiracles, or the holes 

 through which they breathe, are above it. I 

 have elsewhere mentioned that, in all insects 

 which fly, it seems to have been the object of 

 nature to carry rather the air to the blood, than 

 the blood to the air ; and how excellently adapt- 

 ed to this purpose is the tubular and ramified 

 structure of their respiratory apparatus, must be 

 sufficiently evident. 



