INSECTS IN GENERAL. ¥J 



alone or with others, as if the former were essential to the 

 use of wings, but unimportant to the animal while using its 

 legs only for motion. 



It is hardly possible to convey a sufficiently intelligible 

 description of these compound eyes, without the aid of figures 

 drawn with the assistance of a powerful microscope, with 

 which we shall endeavour to illustrate the subject. Fig. 1, 

 represents the head of Papilio Uticce, with the spiral tongue 

 in situ (to which organ we shall refer more at large when 

 treating of the lepidoptera in particular), with the left palpi 

 removed from the side of the tongue ; this is drawn from the 

 reflected image in the lucernal microscope magnified thirty- 

 four times in diameter, and is intended generally to display 

 the outline of the head, and particularly the straight filiform 

 hairs or ciliae, with which the whole hemisphere of the eye 

 is beset at right angles with its surface, and which act pro- 

 bably as eye-lashes to defend the lenses. 



The eye itself presents under the microscope a vast num- 

 ber of apparently hexagonal facets or lenses slightly convex, 

 and separated from each other by slight ridges, forming 

 as many sockets, from which proceed the eye-lashes ; the 

 lenses are, in fact, circular, and their sockets appear in some 

 lights hexagonal, but this hexangular appearance seems to 

 be occasioned by the intersections of the edges of the lenses. 

 Fig. 2, shews one of these lenses magnified two hundred 

 thousand times in surface Fig. 3, represents the sockets 

 and the circles, and Fig. 4, the mode in which the circular 

 lenses display an hexagonal surface. 



These facets or lenses, and their sockets, form altogether 

 a hard elastic membrane, which is of itself very transparent, 

 and constitutes the exterior coat or cornea of the eye ; each 

 facet may be considered a distinct cornea, or the whole of 

 them may be said to form one aggregate cornea. They are 

 convex on the outer surface and concave within, but thicker 



