4QO 



NEUROPTERA 



FIG. 251. Perla maxima. 

 (After Pictet.) 



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 three-jointed, 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- 

 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-iiotum. 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, 

 showing tracheal gills. Pyre- 

 nees orientales. 



