300 ENTOMOLOGICAL NEWS [Dec., '22 



Figs. 9-12 then, represent the ontogenetic stages in Gotnphus 

 corresponding to the stages in Anax of figs. 1-3. The succeed- 

 ing stage is shown in figs. 13 and 14, wings which are 0.4 and 

 0.45 mm. long, and corresponds to that of figs. 4-7 of Anax. 

 The differences in the sub-costa of figs. 13 and 14 are interest- 

 ing, as is also the presence of an additional trachea between R 

 and M in figs. 11 and 14, since such was never observed in 

 Anax, 



Can we derive from the foregoing observations any clew as 

 to the identity of the vein Rs; can we now determine whether 

 the trachea crossing Ml and M2 really represents Rs and that 

 we should therefore call the vein which forms along its course 

 and in the adult lies posterior to M2 the radial sector ? 



Needham has shown that in many insects the veins of the 

 adult may be formed independently of the tracheae and that a 

 vein is not always supplied by its corresponding trachea. In- 

 deed in the wings we are now considering, we see that the costa 

 receives its tracheal supply in great part from the subcosta 

 and radius. There is, therefore, no a priori reason for assum- 

 ing that the trachea called Rs may not, although it is a branch 

 of R, be supplying a vein which is a true branch of the media, 

 especially since Tillyard has shown that in Uropetala the vein 

 Rs is supplied by a branch of M as well as by a branch of R. 



Referring again to our figures we note that the radius in the 

 very earliest instars (figs. 2, 3, 9, 11, 12) usually shows two 

 branches and that in the next instar it most often has two 

 groups of branches (figs. 4, 5, 13, 14) representing the same 

 two branches ; and in addition to these a fine tracheal branch 

 which passes backward and crosses over the two anterior 

 branches of the media. The differences between R in figs. 4 

 and 5 and the same trachea in figs. 6 and 7 are easily explained 

 by referring back to the conditions found in the preceding in- 

 star. All of the principal tracheae in this first stage are sim- 

 ple, they are not composed of fascicles of fine branches as in 

 the two later instars. In passing from this instar to the next, 

 the two branches of R seen in figs. 2 and 3 develop branches 

 equaling themselves in caliber and pursuing a course more or 



