400 



NEUROPTERA 



CHAP.. 



This suggests that it may come from these sternal orifices. The 

 abdomen consists of ten dorsal plates, the 

 first being short, and of nine ventral; 

 the dorsal plates are much more ample 

 transversely than the ventral. Frequently 

 the hind body is terminated by two long, 

 many-jointed cerci, looking like antennae. 

 The coxae are small, not prominent, and 

 are directed outwards. The legs are 

 slender, the tibiae often grooved. The 

 tarsi are threcrjoirited, terminating in two 

 claws and a more or less distinct pad. 

 In the genus Isopteryx an auditory organ 

 has been described as existing in the legs, 

 in a position similar to that of the analo- 



FiG. 251. Perla maximxi. 

 (After Pictet.) 



gous structures 



in Termitidae 



and Blattidae. 

 The. wings when closed repose flat on the 

 back, and fold and overlap so that only 

 one is seen (Fig. 251); in this state 

 the costal portion of each front wing is 

 turned downwards, so as to protect to 

 some extent, the sides of the body. 



The early stages are known, but have 

 not been described minutely, and there 

 appears to be very little information as 

 to the youngest life. All the species 

 are, when immature, aquatic in their 

 habits ; the larvae greatly resemble the 

 perfect Insects in form, though differing 

 in not possessing wings and in the 

 ocelli being merely opaque spaces. 

 They have rather large compound eyes ; 

 the future wings are represented by 

 lobe - like prolongations varying in 

 length according to age ^of the meso- 

 and meta-notum. . In the Nemourae the 

 cerci are absent in the imago though 

 present in the young. The larvae of Perlidae are carnivorous 



Fig. 252. Perla sp., nymph, 

 sliowing tracheal gills. Pyre- 

 nees orieutales. 



