172 ENTOMOLOGICAL NEWS [Apr., '17 



chea. If this trachea be conceived as a new development from 

 the median stem, I see no particular objection to labeling it 

 Ms ; it it be the old original branch from radius that has found 

 a new basal attachment it should still be labeled Rs; but the 

 vein which follows it I cannot believe to be other than Rs of 

 Anisoptcran wings. As to the adult vein. I entirely agree with 

 Mr. Campion in the opinion expressed in his letter of March 

 i8th last when he said: "That the Zygoptera do not possess 

 Rs at all is a rather startling proposition and hardly one which 

 can be accepted offhand. In Zygopteran and Anisopteran 

 wings alike we find six longitudinal veins to be all located be- 

 tween R and M. These veins occupy exactly similar positions 

 in the two kinds of wings, and I find it exceedingly difficult to 

 believe that they are to be interpreted in one way in the Zygop- 

 tera and in another way in the Anisoptera." 



Tillyard demands ontogenetic evidence ; and yet, singularly 

 enough, in support of his "unbranched radius theory" he of- 

 fers just the evidence I lacked to give me the greatest assur- 

 ance in the other interpretation. This evidence is not from 

 tracheae, however, but from cuticularization of the nymphal 

 wing — a sort of evidence which he himself stresses heavily in 

 support of his theory concerning the development of the anal 

 area of the wing. This cuticularization (anticipatory vena- 

 tion) of the nymphal wing he shows in his text Fig. 5 (Proc. 

 Linn. Soc. N. S. Wales, 40; 227). This shows an actual cross- 

 ing, for which Dr. Ris' statement that it is "preparatory to the 

 development of the imaginal venation" is no explanation what- 

 ever. There is nothing like it in insect wings, except in ob- 

 lique veins where tracheae either are present or have been 

 present in earlier stages of development. This crossing fol- 

 lows exactly the course taken by the trachea Rs in the more 

 generalized Anisoptera and is probably the channel which that 

 trachea once occupied. It is for me a most satisfactory con- 

 firmation of the identity of the vein Rs of the two suborders 

 of Odonata. 



Such differences of interpretation grow out of dift'erent 



