THE NEUROPTERA. 185 



The consideration of these circumstances, and 

 especially of the variation in the metamorphosis, has 

 induced many foreign entomologists to divide the 

 Neuroptera into two orders, and this has also been 

 done, but in a different way, by British entomolo- 

 gists. To avoid making an unnecessary number of 

 primary groups, however, I shall follow neither of 

 these methods, but regard the Neuroptera as a single 

 order, divisible into three suborders. 



The principal bond of union between these insects, 

 some of which are evidently nearly related to the 

 Orthoptera, consists in the structure of the wings, 

 which are almost always present to the number of 

 four, of a membranous texture, and traversed by 

 numerous veins, which are usually very numerous, 

 and form a close network in the wing. Both pairs 

 of wings are employed in flight, and they are usually 

 nearly equal in size, although in some cases the lower 

 wings are larger than the upper pair, and folded up 

 beneath them during repose, but the anterior wings 

 are never converted into horny or leathery elytra. 

 In the May-flies again, the hinder wings are much 

 smaller than the anterior pair, and in some exotic 

 species belonging to the order, they present remark- 

 able peculiarities of form; but with these we have 

 nothing to do. 



The organs of the mouth are generally well deve- 

 loped, and adapted for biting, although in one or two 

 groups they are reduced to a rudimentary condition. 

 The head is variable in form, furnished with a pair of 

 large compound eyes, and usually with two or three 

 ocelli, and bears a pair of antennae, which are either 

 elongated and thread-like, or short and bristle-shaped, 

 rarely clavate. The thoracic segments are distinctly 



