48 



ENTOMOLOGICAL NEWS 



[Feb. ,'22 



cated by 0' and the long bridge ; the trachea which first cap- 

 tured the line of Ms via O' becomes ousted by the subnodal 

 trachea, and the result is that we get the formation seen in the 

 larvae of almost all Anisoptera at the present day, viz., a single 

 oblique vein O, placed not far distad from the level of the 

 nodus, a short bridge vein, and an apparent trachea Rs supply- 

 ing the course of the vein Ms. 

 N 



Sc 



Text-fig. 2. Diagrams to show the evolutionary stages in the region of the nodus and 

 oblique veins in Odonata. A-B, the primitive condition, in which the imaginal venation 

 corresponds with the larval tracheation, and no oblique veins are present. C, formation 

 of the long bridge and distal oblique vein, as in Lestidae. D, condition seen in Petalu- 

 ridae, with short bridge and two oblique veins. E, condition present in the majority of 

 Anisoptera, with short bridge vein and only the more basal oblique vein present. 



Text-fig, 2 shows the tracheation of the larval wing for each 

 of these evolutionary stages. 



If this outline of the evolution of this portion of the larval 

 and imaginal wings be accepted, we must recognize the Zygop 

 tera and the Anisozygoptera as the first two Suborders to 

 appear by differentiation of the original Odonite stock, and we 

 must allow that the Anisoptera only arose later, from some of 

 the more specialized types among the Anisozygoptera. That 

 this was actually so, I believe can be fully proved by a careful 

 study of the known fossil record, as- I shall endeavor to set 

 out in a later part of these researches. 



We have now to deal briefly with one line of criticism that 

 will most certainly be levelled against the position taken in this 

 paper. In his original paper (1), Needham gave drawings of 

 the positions of his supposed trachea Rs in the developing 

 stages of the larva of a species of Gomplms. No photographs 

 were given of any but the last instar. In these drawings, it 



