128 INSECT MISCELLANIES. 



from the circumstance of its being- thus furnished 

 with two pair of eyes. One species of this {Tetrojjs 

 jyrajusta) is found in the vicinity of London. 



a, Tetrops presusta ; &, eyes of ditto very greatly magnified. 



Fabricius, who is followed by Olivier, considers 

 one pair of these eyes as nothing more than a spot ; 

 but accurate examination shows that the principal 

 facetted eyes are actually divided by the crossing of 

 the corner {canthus), which in other insects of this 

 family {Cei^ambycidce) only enters, and indents a 

 portion of the eye without dividing it entirely *. What 

 is not less singular, the males of more than one spe- 

 cies of day-fly {Ephemera), besides the regular num- 

 ber of facetted and coronet eyes, have a pair of facetted 

 eyes on the top of a short columnar projection. 



In the little whirlwig (Gyrinus nataior) that 

 skims about so merrily on standing water, the upper 

 portion of the eyes, fitted for seeing in the air, is 

 placed on the upper part of the head, and the lower 

 portion, fitted for seeing in water, in the lower part, 

 a thin division separating the twof. 



a, Gyrinus natator ; b, eyes of ephemera very greatly magnified. 



When a facetted eye, such as that of a butterfly, is 



* Kirby and Spence, Intr. iii. 498, &c. 

 t See bisect Transfunnations. page 370. 



