286 Memoir upon the compound 



the two kinds of eyes, have scarcely given me any information as 

 to the destination and utility of the former. 1 removed with 

 the greatest care the smooth eyes from the ves/m gntlica and 

 vrtlgaiis, as well as from the apis viulucea and other hymeno- 

 pterce, and from the opis philanlhus and scvlia. At the moment 

 of their heing removed, the privation seemed to retard their 

 movements a little ; but soon afterwards thev acted as before. 

 I never saw the wasps whose smooth eye;> 1 had removed ot 

 varnished over, at all embarrassed in taking fiight again. The 

 case v.'as the same with the ortliopierfs which 1 suijinitted to si- 

 milar tests : in short, all continued to move as before. 



When, on tlic contrary, I pa-sed a blackish varnish over the 

 compoui'd eves, or wlien I burst them, I saw the insects act 

 completely as if they were blind, turning about in all directions, 

 ■without being able to guide themselves. Thus they briishtd 

 against the wall, or any obstacle which I placed bclbie tlietn. 



All the insects which I r-ubjccted to this kind of test seemed 

 to draw their legs very frecjuently over their heads, as if to re- 

 move what hindered their eye-sight, hi this state we also saw 

 thern make more frequent use of their antennse, by directing 

 them always forward and on one side, and feeling with the 

 greatest celerity the objects vvhicii opposed their progress. This 

 greater mobility of the antenna; ainiounced pretty well their uses: 

 but in order to render them still more evident, I took some lo- 

 C7istcB which have the antennae very long, and I touched these 

 organs with oxy-mm-iatic acid. The insect was noways affected 

 thereby ; but as soon as this acid came near the eye-lids, and 

 long before it could produce an immediate action on the ere 

 itself, the insect darted away with rapidity, showing a great de- 

 gree of anxiety. This exjjeriment, which 1 repeated several 

 times, and which always succeeded, seems to confirm an opinion 

 which I formerly hazarded on the use of the antennae and the 

 palpebrffi in certain classes of insects*. 



In short, if we remove from the insects which have not com- 

 pound eves, their smooth eves, or if we cover them with an 

 opaque varnish, we see them act as blindly as those which are 

 deprived of their compound eyes. This experiment proves that, 

 when insects have no other eyes than simple eyes, the latter per- 

 form the offices of comj)ou!id eves. As to the smooth eyes 

 ■united in the same individual to the compound eyes, they seem 

 to be of very little use. Perhaps they are merely destined to serve 

 for the vision of objects which strike directly the point where 

 these eves are situated. Thus, the lateral eyes placed on the la- 

 teral summits of the head, would be destined to show the insect 



* Vide iiiy Memoir on the Sense ol"Siiicllir,!r, and on the Or'.'niis wbicli 

 icem to be tiic Scut of it, iu the Annuka du Museum d'Hisl. Hat. 



all 



