I II \l\ I. 



DEFINITION AND STRUCT! RE OF 1NSK( rS. 



I I 



compare the patterns of neuration exhibited by wings of 

 belonging to widely-separated Orders- 



The wings themselves are usually more or less triangular but 

 the shape is extremely various and often greatlj modified. The 

 wings may. for example, be deeplj cleft (as in the Pterophoridae 



Fig. 12. Wings ol Oriieodes-microscopica, showing deep clefts. lAuthi 

 original sketch from Spolia Zeylanica.) 



and Orneodidae), extremely elongated (as in the hindwings of sonic 

 Nemoptera), or modified to form stridulating organs (see figure 26). 

 They may be naked or covered with hairs or scales or both. The 

 portion which is articulated to the thorax is called the base of the 

 wing, the anterior margin which is nearest to the head is called 

 the eost.i. the margin opposite the base is tailed the termen or 

 outer-margin, whilst the posterior edge is called the dorsum or 

 inner-margin. The tip ol the wing .11 the junction of costa and 

 termen is called the apex and that at the junction of the termen 

 and dorsum is called the tornus or inner angle. 



The Abdomen cinJ its appendages. 



rhe abdomen, or body proper, consists oi about eleven more or 



less similar segments, although many of these are often greatlj 



modified and are difficult to trace, so that not more than seven or 



eight may actually be visible. The abdomen is often remarkably 



extensile, this mobility being permitted by the arrangement of the 



nents which are arranged below one another during contraction 



see figure 2) but which can be widely separated l>\ the extension 



of the membrane which connects them. Along the sides of the 



abdomen are found the spiracles (see Respirator) System) and 



the extremity of the body may be provided with cerci or other 



