208 SYSTEMATIC ARRANGEMENT. 



the inner edges approximate when closed, hut the 

 one usually overlaps the other. Although, for the 

 most part semi-membranous, they vary considerably 

 in consistency in different trihes. In certain specie 

 of Mantis, for example, they nearly assume the 

 appearance of transparent reticulated wings, whil 

 among the convex-hacked Blattce they approac 

 to the rigidity of elytra. They are generally re 

 ticulated by a series of strong nervures, radiatin 

 from the base to the summit, and crossed by 

 multitude of smaller ones, resembling fine lace 

 Sometimes, however, these nervures are visible onl 

 at the apex of the tegmina, but their existence 

 always obvious on the under side. Among th 

 Grytti, the males of which are provided with a musica 

 apparatus, situated at the base of the abdomen, som 

 of the nervures are much more prominent than others 

 and instead of being longitudinal, are curved in 

 variety of ways ; it is by rubbing these against th 

 apparatus mentioned, that these insects produce th 

 peculiar noise for which they are remarkable. 



The under wings being adapted solely for fligh 

 are of a much more delicate texture than the superio 

 pair. They are traversed by a series of pretty stron 

 parallel nervures, diverging from the base, and ar 

 folded up and expanded nearly in the same manne 

 as a fan. From this cause they cannot be packe 

 in so small a compass as in beetles, the wings o 

 which are folded transversely upon themselves ; ac 

 cordingly, they are not always quite covered by th 

 tegmina when at rest, and in some instances the 



