122 Annals Entomological Society of America [Vol.11, 



base of the wing. The medial trachea is suggested merely by a 

 very faint and delicate but constantly appearing tracing in the 

 wing. 



As in the wings of Aphididse and Psyllida) the radial trachea 

 in Aleurodidae is branched, being represented by the branches 

 corresponding to Ri and Rs. And as in the hind wing of all 

 aphids and the front wing of the Chermesinae, and the hind 

 wing of psyllids, the vein radius in Aleurodes is unbranched, R^ 

 being lacking. The formation of the vein radius in Aleurodes is 

 of exceeding interest. It follows the course of the radial trachea 

 ■ to the branching of the trachea and then proceeds along the radial 

 sector. Rj in the mature wing is lost and its position, if indicated 

 at all, is suggested by the most delicate "shadowing" in the wing 

 tissue. As has been previously stated,* the "complete absence 

 of vein Ri" was predicted as characteristic of the Hemiptera on 

 the basis of the two widely separated insects, — the Cicada and a 

 Coreid, and the phylogenetic significance of the added testimony 

 of the weakness of this vein and the trachea that precedes it, 

 in the remote and highly specialized group of Homoptera here 

 under consideration seems to the highest degree interesting. 



The tracheation of Aleurodicus I have not had -an opportunity 

 •to study. On the basis of figures of the mature wing (not a safe 

 basis for this group by any means, as has been shown), however, 

 the additional vein found there can only be interpreted as R^. 

 Its prominence is to be accounted for here doubtless, as in the 

 case of its prominence in the forewing of the psyllid, by the round- 

 ed shape of the wing which results in a large wing expanse not 

 otherwise strengthened. In response to mechanical necessity 

 this vein, weak or absent when not needed, becomes more strongly 

 developed. | ..: [^ 



The second vein of the wing of Aleurodes is cubitus as will be 

 seen by comparing figures 44 and 45 where the second vein is 

 shown to follow the course of the cubital trachea. 



The hind wing of Aleurodes (fig. 46) has but one trachea and 

 one vein, — the radial sector it seems inevitable to conclude. 



COCCID^. 



Before examining wings of freshly emerged male coccids it 

 seemed possible only to echo the sentiment of Redtenbacher, — 

 "Cocciden konnte ich nicht iintersuchen.'"^ Imagine the surprise. 



* See Page 119. 



t Vergleichende Studien uber das Flugelgeader der Insektcn. Page 188. 



