58 



THE GENERAL FEATURES OF WINGS 



The anal area and the preanal area.-^In descriptions of wings it is 

 frequently necessary to refer to that part of the wing that is supported by 

 the anal veins ; this is designated as the anal area of the wing ; and that part 



of the wing lying in front of 

 the anal area, including all of 

 the wing except the anal area, 

 is termed the preanal area. 



The furrows of the wing. 

 — There are found in the 

 wings of many insects one or 

 more suture-like grooves in 

 the membrane of the wnng; 

 these are termed the furrows 

 of the wing. The following 

 furrows have received dis- 

 tinctive names. They occur 

 chiefly in the fore wings. 



The anal furrow. — The 

 anal furrow is the one of the 

 furrows of the wing that is 

 most often present. It is 

 developed in the cubito-anal 

 fold; but in many insects 

 where there is a well-devel- 

 oped cubito-anal fold there is 

 no definite, suture-like anal 

 furrow. 



The anal furrow is usually 



either between the ciibitus 



and the first anal vein or it is 



it may supplant in forms in 



This is the case in the 



Fig- 39- 



-Wings of Bombyx mori. 



coincident with the first anal vein which 



which the venation of the anal area is reduced 



Lepidoptera and the Diptera and is well-shown in the wings of Bombyx 



mori (Fig. 39), in which a vestige of the first anal vein is preserved near the 



margin of the wing. 



In the Hymenoptera, where the anal furrow is developed between the 

 cubitus and the first anal vein, it cuts through those veins, the tips of which, 

 coalescing with the anal veins, crosses its course (Fig. 40). 



In those Heteroptera in which we have been able to determine the veins 

 in the fore wings, the anal fun-ow has been developed in front of the cubitus 

 (Fig. 41, a/). 



A study of the musical organs of adult Orthoptera throws light on the 

 nature of the anal furrow. In the female this furrow lies in its usual posi- 



