NEUROPTERA : STRUCTURE. 365 



the nings are of equal size, as in the di-agon-flies, Panorpa, 

 &c. ; in others the posterior pair are considerably smaller 

 than the others, especially in the Ephemeridaj in which, 

 indeed, the posterior wings occasionally are entirely evanes- 

 cent. In Nemoptera the posterior pair are much longer than 

 the anterior, and very slender. 



These insects have the head of a large or moderate size ; 

 the eyes, which are lateral, sometimes occupy nearly the 

 whole of this part of the body ; the ocelli are placed on the 

 forehead ; the latter are, however, wanting in some species, 

 as in Myrmeleon, Osmylus, &c. ; the antennae are frontal, 

 and of very different forms, being very short, and resembling 

 a fine bristle, in the LibeUulid(S and Ephemeridoe ; long and 

 clubbed in Ascalaphus and Myrmeleon ; and filiform or 

 setaceous in the others. The mouth consists of the ordinary 

 organs composing a mandibulated mouth, the maxillce being 

 very robust, and the tongue well developed, in the dragon- 

 flies. In some species, as the Perlidce, Hemerobiidce, &c., 

 the construction of the trophi is almost identical with that 

 of the Orthoptera. In the Ephemeridcs, which are destined 

 to live but a day in the final state, the mouth is rudimental 

 and almost obsolete. In the dragon-flies the palpi are also 

 very minute, whilst in the Myrmeleonidce they are long and 

 slender. In the Panorpidce the front of the head is pro- 

 longed into a kind of rostrum, at the extremity of which the 

 trophi are placed. 



The legs of these insects are of a moderate size ; flight 

 being the chief mode of locomotion in the imago state, the 

 legs do not acquire that degree of developement which we 

 find in some of the cursorial and saltatorial species ; the tarsi 

 vary in the number of joints in the different species, there 

 being five in the Hemerobii, Fanorpce, &c,, four in the Raphi- 

 diis, three in the hihellulce. In all they are terminated by two 

 small hooks. The abdomen is long, cylindrical, or com- 



ii3 



