548 



THE PAXORPOID COMPLEX, 111., 



C (rarely present), .simple; Sc, forked distally; Ri, simple; 

 Rs, four-branched; M, four-branched; Cu, two-branched; 1A, 

 2A, 3A, all simple. 



3A 2A 1A Cu 2 



Text-Fig. 37. 



Hypothetical Type of Wing-venation, according to Comstock and Need- 

 ham. (From Comstock). c-r, costo-radial basal trachea; cu-a, 

 cubito-anal basal trachea. Other lettering as on p. 535. 



This hypothetical type is shown in Text-fig. 37. 



My attempt to apply this type of venation as archetypie for 

 the Orders of the Panorpoid Complex did not meet with suc- 

 cess ! and I was soon forced to conclude that this hypothetical 

 type needs considerable alteration, before it can be accepted as 

 typical for the original scheme of the wing-venation in these 

 Orders. There is no doubt whatever about the correctness of 

 the hypothetical arrangement of the trachea? as having been 

 originally in two groups entering the base of the wing separately, 

 as will be seen from Section i. Nor can I find any flaw in 

 Comstock's argument (15) as to the original dichotomic 

 manner of arrangement of the branches of R and M. These 

 points are accepted in this paper. But, with regard to the 

 number of branches of the main veins, I am quite unable to 

 accept Comstock's conclusions. In this Section, I propose to 

 review briefly the evidence concerning the condition of branching 

 of each main vein, in the Archetype of the Complex. Text-fig. 

 38 shows the venation of this Archetype, as worked out in full 

 in this Part. 



The Costa and the Subcosta. 



A separate costal trachea is sometimes present in the pupal 

 wing, as, for instance, in the Megaloptera (15, fig. 166) and 

 in the Diptera (Text-fig. 50) . In the fossil genus Archipanorpa, 



