and smooth Eyps of lined s. 109 



smooth or simple eves, on account of their simplicity. These 

 two kinds of eyes concur to the snme object, and are sometimes 

 united on the' same individual: thus, thfi or I hoplcrce, Wke. Xh^ 

 hymenaptcrce, present at o;.ce both compound and simple eyes, 

 a <lisposilion which is also observed in various kinds of hemi- 

 pterce, veutvptcice, and dipleire. The other classes present only 

 a single kind of eye ; but when there are only smooth eyes, their 

 number is always consii!eral)le, jirobably in order to make up for 

 their imperfection. In general, all winged insects have com- 

 pound tve-!, and this law does no! seem to present any exception, 

 lii the nplerce, certain kinds present only compound ideas, such 

 as the clopnrloe: in truth, the latter seem formed by a collection 

 of simple eves. Other kinds have only simple eyes, such are 

 the Juice and the scJopendrce, which present a certain numbei* 

 of simple eyes; but ail these animals appear to me so different 

 from the insect tribe in poiiit of organization, that I have thought 

 it riglit to pass them over. 



With respect to the huvae, those of half-metamorphosed in- 

 sects uniforndy have eyes similar to those of the perfect insects; 

 whereas the larvae of insects wholly metamorphosed have only 

 simple eves, which vary much in their number and position. 

 T!ie caterpillar has six or eight on the sides of the head. The 

 false cater}>illars, or the larvae of common flies, have two only, like 

 those of bees and the stratyowa. Finallv, a great many com- 

 pletely metamorphosed larvae have no eyes at all. 



We may also remark, that the species which exhibit both com- 

 pound and simple eves (which has never been observed but in per- 

 fect insects) are those which have most need of seeing far, either 

 because by rising high in the air it is recjuisite that they should 

 distinguish their prey at a certain distance, or because, having 

 large flights to take, they should direct themselves witli safety. 

 In short, the insects of a great flight, like birds of prev, have very 

 delicate and very extensive powers of vision. 



But in order to give an exact idea of the two kinds of eyes of 

 insects, we shall descriljc each in particular, commencing with 

 the compound eyes, the organization of which is most compli- 

 cated, r.iid terminating our description by the simple eves. We 

 jhali afterwards endeavour to ascertain in what way the faculty of 

 vision is executed among this ortler of animals, when we have 

 followed up all the ditfercii<;es of organization which they pre- 

 bent with respect to tliclr eyes. 



1. Compound eijf-x. Tlie compound eyes are generally .si- 

 tuated on the lateral or middle parts of the head, sometimes 

 even comjjietcly at the base of it, and a fevv are jjlaced near the 

 antenna?, or more or less laterally and outside of these parti. 



Placed 



