410 Dr. T. A. Chapman on Acanthopsyche opacclla. 



Rj, and that these two trachese passed together to tlie 

 termen of the wiog and formed the basis of vein 8 (Meyrick). 

 Since vein R^ originated at some distance from the base 

 of the wing, the jDosition where the two veins joined was 

 marked by a transverse vein, the bar between 8 and the 

 cell present in many families. 



The further progress of this condition took two directions, 

 or rather had two elements. The first was a tendency of 

 the bar to travel to the base of the wing. The extreme of 

 this condition is found in Papilionids, Vanessids and Pierids, 

 possibly in all butterflies, but I have not yet examined 

 skippers or Lycoenids, in which vein 8 possesses both 

 tracheee from the base of the wing to the termen. 



The other change was for one or other trachea to atrophy 

 beyond the bar. In Sphinx R^ disappeared until only 

 sufficient remains to form the bar. 



In PolyplociclRi both changes took place, vein 8 is en- 

 tirely Rj, originating close to the wing base, and the 

 subcostal is only a minute trachea almost lost in the wing 

 base. 



In A. opacdla the condition present is an atrophy of the 

 subcostal beyond the bar, the vein 8 up to the bar is 

 subcostal, beyond it Rj. In this respect it agrees with the 

 few Caradrinids I have examined. 



Plate VIIL 



[/See ex2'>lanatluih facing the Plate.] 



