PHYSOPODA. NEUROPTERA. 153 



eyes ; the latter are of moderate size, and granular in their ap- 

 pearance ; and between them, on the crown of the head, there 

 are generally three ocelli. The legs are of moderate size, and 

 terminated by two-jointed tarsi ; the second joint bears no claws, 

 but is furnished with a soft vesicular pad, which enables the 

 insects to cling firmly to any object on which they may be 

 walking. These insects are nearly all of minute size, rarely 

 exceeding an eighth of an inch in length ; one or two Australian 

 species, however, are larger ; the Idolothrips spectrum measuring 

 about a third of an inch long. They run actively, and some of 

 them are able to leap to a considerable comparative height by 

 means of their abdomen, which they employ in the same way 

 that the Podurce do their furcate caudal appendage ( 803). 



734. They are herbivorous in their habits, and are generally 

 found in the flowers of plants, where, from their slender forms 

 and dark colours, most of them appear like little moving lines. 

 Some species live upon the stems and leaves of plants, to which 

 they often do considerable injury. This is the case with the 

 Thrips cerealium, which attacks the wheat crops, either gnawing 

 the stems when tender, or destroying the flowers and young 

 grain. According to an Italian writer, the whole wheat crop of 

 Piedmont was destroyed by this insect in the year 1805. A few 

 species also live under the bark of trees and in rotten wood. 



ORDER IV. NEUROPTERA. 



735. The Neuroptera, like the Coleoptera and Orthoptera, 

 have a mouth adapted for mastication, but differ from them as to 

 the conformation of the wings ; the anterior as well as the poste- 

 rior pairs being here membranous and usually 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. 471). Although the posterior wings are usually as large 



