ENTOMOLOGY. Ill 



mesothoracic pair is called the anterior, upper, or 

 primary wings ; the metathoracic pair, the posterior, 

 under, or secondary wings. When a single pair only 

 exist, they are attached to the mesothorax, except in 

 one recorded instance, the Asckipkasma annulipes, 

 which has posterior wings without the least trace of 

 an anterior pair. 



In general form, structure, and relative size, they 

 undergo a great variety of modifications in the diffe- 

 rent orders ; and it is from these modifications that 

 the respective orders derive their names. Sometimes 

 all the four are of similar membranous structure, and 

 either all equal in size, (Neuroptera?) or the anterior 

 pair largest, (Hymenoptera, &c.) At other times, 

 the anterior are rigid and horny throughout their 

 whole extent, (Coleoptera,) or only on one-half of 

 their surface, (Hemiptera Heteroptera.) In some 

 instances, (Ortkoptera, &c.) the anterior wings are 

 what is called pergameneous that is, of a substance 

 between coriaceous and membranous, or somewhat 

 resembling parchment. 



The harder the substance of which wings are com- 

 posed, the less active is the share they take in flight. 

 When they consist entirely of a hard horny substance, 

 (as among the Coleoptera,) they can be subservient 

 to this use in a very trifling degree ; their primary 

 and important function being to protect the inferior 

 wings and the abdomen. They are, accordingly, 

 distinguished by a name significant of their use, 

 namely, elytra, sheaths or coverings. In proportion 

 as the membranous portion of the wing gains upon 

 the denser part the wing becomes a more efficient 



