THE WINGS OF ODONATA 239 



J. O. Westwood for the work on Fossil Insects by Brodie ('45). Figure 239 

 is a photographic reproduction of Westwood's figure. 



It is evident from Professor Westwood's figure that while the venation 

 of the wing is not well-preserved in some parts of the wing it is distinctly 

 preserv^ed in the anal area. 



The basal anal area. — ^At the base of the wing there is a defiintely out- 

 lined area, which is bounded in front by vein Cu+A, distally by the anal 

 crossing, and behind by the secondar\^ anal vein, vein A'. This ma\' be 

 termed the basal anal area (Fig. 230, ha). 



The cubital area. — That area of the wing which lies between the main 

 stem of cubitus and the anal vein, and which is bounded proximally by the 

 anal crossing, may be termed the cubital area (Fig. 229, ca). This area 

 corresponds to cell Cu of insects with few wing-veins. In many genera this 

 area consists of two cells, the second of which is the subtriangle (Fig. 230, t'). 



The anal triangle. — In some of the Anisoptcra there is a well-marked 

 triangular area which is bounded in front by vein A' and distally by vein 

 A3; this is known as the anal triangle (Fig. 230, at). 



The membranule.- — In the Anisoptera there exists at the base of the anal 

 area a portion of the wing which is not traversed by veins and which is 

 usually of darker color than the adjacent parts of the wing; this is the 

 membranule (Fig. 230, m). 



The chief cubito-anal cross-vein. — There is a cross-vein that extends 

 across the cubital area from the main stem of cubitus to the anal vein that 

 is present in so large a proportion of the members of this order and which is 

 of so much taxonomic importance that it merits a distinctive name. It has 

 been termed the second cubito-anal cross-vein ; but this name is no longer 

 tenable, the so-called first cubito-anal cross-vein being a part of the anal 

 vein, the anal crossing; the term chief cubito-anal-cross-vein is, therefore, 

 suggested for this vein (Fig. 229, cu-a). 



The subtriangle. — That part of the cubital area of the wing that is 

 beyond the chief cubito-anal cross-vein, and which is bounded on one side 

 by the triangle, is termed the subtriangle (Fig. 230, t')- The subtriangle 

 may be a single cell or it may be divided by cross- veins (Fig. 237). 



The subtriangle is not so constantly a definite area of the wing as is the 

 triangle; for in many genera it is not distinctly set off from the remainder 

 of the cubital area, owing either to the absence of the chief cubito-anal 

 cross-vein, or to the presence of several cross-veins, making it difficult to 

 determine the chief cubito-anal cross-vein (Fig. 237). 



The anal loop. — In many of the Anisoptera the broadly expanded anal 

 area of the hind wings is strengthened by an arrangement of certain of the 

 veins which has been designated the a)ial loop. The anal loop is found 

 especially in the subfamily Aeschnina^ and throughout the family Libel- 

 lulida?, and varies greatly in form in the dift'erent members of these groups. 



