4? 



And their feelers, besides their use in cleaning the 

 eyes, are a good guard to them in their walk or flight, 

 enabling them by the sense of feeling to discover an. 

 noyances, which, by their nearness^ might escape the 

 sight. 



The eye of a fly is in truth an assemblage of multi- 

 tudes, often many thousands of small eyes. Nature 

 has given each lly two large reticular eyes (that are 

 covered with a kind of net-work.) And as each 

 contains such a multitude of smaller eyes, one would 

 imagine this might suffice. Yet some flies have four 

 reticular eyes ; the two smaller are placed as usual, 

 the two larger are behind the other on the upper part 

 of the head. 



In different species the reticular eyes are of dif- 

 ferent colours. Some are brown, some yellow, green, 

 red, and this in all the different shades of those 

 colours. And some have the gloss of metals highly 

 polished. 



But beside these, many species of flies have a sort 

 of eyes, which are not reticular, but of a perfectly 

 smqoth and even surface, and far smaller than the 

 reticular. Three of these are on the back of the head 

 of vast numbers, which are triangularly placed. Some 

 have more, and some have less than three. Gnats 

 have none of them. Their heads are in a manner co- 

 vered with their reticular eyes, so as to leave no room 

 or occasion for smooth ones. 



Nor are these smooth eyes peculiar to flies. Other 

 insects also have them : the grasshopper in particular 

 has two, which are placed near the nose. 



3. The species of insects are almost innumerable. 

 All of these some suppose to have no heart, as they 

 have no sensible heat, none that can be perceived 

 either by the touch, or by any other experiment. But 

 this is a mistake. Many indeed have not such a heart 

 as other animals have : but all have something analo- 

 gous to it, something that answers the same purpose. 



Same likewise have thought that insects have no 



