GENERAL CHARACTERS OF NEUROPTERA. 147 



effects a clearance much more speedily than any other cause could 

 do. Of the cause of the occasional appearance of the Locusts, in 

 such vast multitudes, no satisfactory explanation has been given. 

 Of these Insects there are several different species, which are 

 distributed over the tropical and the warmer temperate regions of 

 the globe ; and in many parts they are used as food by the 

 inhabitants of the countries they infest. 



ORDER III. NEUROPTEEA. 



671. The Neuroptera correspond with the two preceding 

 Orders, in having a mouth adapted for mastication, but differ from 

 them as to the conformation of the wings ; the anterior as well 

 as the posterior pairs being here membranous and transparent. 

 In both pairs of wings, the veins form a very beautiful and 

 minute network, subdividing and uniting again, so as to divide 

 the whole surface into a large number of minute cells, which 

 much exceed in number those of the wings of any other tribe of 

 insects (Fig. 370). Although the posterior wings are usually 

 as large as the anterior, or sometimes even larger, they are occa- 

 sionally much smaller, and may even be altogether wanting. 



675. The body of the Insects of this Order, which contains 

 the well-known Dragon-flies, May-flies, Ant-lions, White Ants 

 or Termites, and others, is generally prolonged, and destitute of 

 any very hard integument. These insects are of intermediate 

 size ; none of them exceeding in dimensions the largest Dragon- 

 flies of this country ; whilst none exhibit the minuteness of some 

 Hymenoptera and Coleoptera. They differ in the character of 

 their metamorphosis, as well as in their adult structure ; for in 

 some the metamorphosis is complete, the larva undergoing a 

 marked change of form; and in others there is not much difference, 

 except in the absence of wings, between the larva and perfect 

 insect. By these differences the Order may be divided into two 

 sections ; in the first of which the insect is active during the 

 whole of its pupa state ; whilst in the second, it is quiescent, 

 except just before its last metamorphosis. The first of these 



