216 WING-VENATION IN ZYGOPTEROtJS DtlAGONFLIES, 



(iv.)Cu bends very little, and is continued on by Cuj almost 

 in a straight line. Oug comes off posteriorly in a gentle curve. 



(v.) A is almost completely suppressed. We can make out 

 (a) a small basal piece, Aj, arising from the alar trunk AT, and 

 running up towards Cu, (6) the severed distal piece, Ac, attached 

 to and depending from Cu as a weak branch a little basad from 

 the level of the arculus. 



The Wing-Tracheation of Calopteryx splendens (Text-figs. 3- 4, and 

 PI. xxxiv., figs. 1-3). 



Dr. Ris's photographs show the last two instars. We notice 

 that : — 



(i.) R is a straight trachea without any branches (as in 

 Di])hlehia). 



(ii.)The basal contact of R and M is very close for a consider- 

 able length. 



(iii.)M is much stronger than R. It has four posterior branches 

 situated as in Diphlebia. But, in Calopteryx, on leaving R, M 

 bends sharply downwards to give off its two most basal branches, 

 and then bends quite as suddenly upwards so as to come to lie 

 again close under and parallel to R before giving off its next 

 branch. The last branch comes off before the subnodus (as in 

 Diphlebia). 



(iv.) Cu bifurcates some distance beyond the level of the future 

 arculus; Cuj runs straight on (as in Diphlebia). Cu, dips sud- 

 denly, curving away distally, but giving off posteriad a short but 

 distinct branch, Cu-.b- 



(v,) A is distinctly seen arising from the alar trunk, AT, and 

 running towards Cu. In the penultimate instar, fine strands of 

 A seem to be present, running just below Cu. (This may be due 

 to displacement). Ac comes off from Cu at a considerable dis- 

 tance from the base (but before the level of the arculus), and 

 turns distad to run beneath and parallel to Cu towards the 

 curve of Cu._,. This portion is clearly Aj. A distinct branch 

 given off posteriad from Aj, at a level just beyond Ac, may be 

 provisionally taken to be Ag. In the last stage, another trachea 

 corresponding to Ac may be seen depending from Cu, between 

 Ac and the base. This formation is, I believe, quite unique. 



