I20 Annals Entomological Society of America [Vol.11, 



psylla c. mamma Rile}' (fig. 39) the tip of Ri has migrated slightly 

 toward the middle of the costal margin. In both these wings the 

 space from the base of the wing to the tip of Rx is evidently too 

 long to bear the strain of flight without further strengthening. 

 This needed reinforcement occurs in the presence of a more or 

 less pronounced stigma the proximal edge of which is margined 

 by a ridge which is in some species so clearly defined as to be 

 frequently figured as a vein. 



As the tip of Rj approaches the middle of the costal margin 

 as in Anomoneura mori Schwarz (fig. 40) and even more in Psylla 

 floccosa (fig. 36) the need of the stigma is removed as Ri strength- 

 ens this portion of the wing margin. 



The wing of Trioza (fig. 37) shows an extreme case of the mi- 

 gration of Rj, this vein being here scarcely longer than the stig- 

 mal ridge in P achy psylla and in about the same position. Cor- 

 related with this condition are other striking departures from the 

 more generalized psyllid wing, perhaps the most conspicuous being 

 the origin of the free parts of media and cubitus at approxi- 

 mately the same point as the origin of the free part of radius, — 

 the common stem M + Cu present in most psyllids being lacking 

 in Trioza. 



The wing of A. mori is in one respect most unusual for the 

 family, and that is in the branching of the radial sector. This 

 is the only instance in the four families discussed in this paper 

 where the radial sector is branched, and it throws additional 

 evidence on the interpretation of this vein as the sector. It 

 should be stated in connection with the discussion of figure 40, 

 that the venation here shown may possibly be not normal for 

 this species. The writer had access to but a single specimen 

 and in this the radial sector of the wing on one side bore five 

 branches as figured while the radial sector of the other side was 

 six branched. 



The purpose of this study in wing tracheation has had the 

 vein homologies as a goal and is not intended to enter into syste- 

 matic discussions. However, since the systematists of the 

 Psyllidae build their tables largely upon the basis of the wing 

 veins,* it is apparent that it would be more satisfactory to apply 



* Low. Verb. g-b. Wien XXVIII. 

 Maskell: Transactions of the N. Z. Institute Vol. XXII, 1889, page 158. 

 Frogatt: Australian Insects. 

 Kuwayama: Trans, of the Sapporo Nat. Hist. Soc. 1907-08. 



