1909] Homologies of Wing Veins 125; 



The interpretation of the so-called subcostal has been*^ 

 that it is a single heavy vein spreading at the distal portion into- 

 the stigma. That this interpretation is incorrect the foregoing 

 discussion on the tracheation has made clear. It is really a. 

 composite structure bordered along the cephalic margin by 

 the subcostal vein and containing the radius and the coalesced 

 proximal portions of the remaining wing veins. 



It will be seen by reference to the accompanying table that 

 the first, second and third discoidals are respectively the ist i\nal, 

 Cubitus and Media. The second anal not persisting in the adult 

 wing (that is, it is represented only by a constantly appearing tra- 

 chea which soon clears) is not shown in any published figures of 

 aphid wings. 



In the hind wings the first and second discoidals are respective- 

 ly (fig. 8) the cubitus and media, and the so-called subcostal vein 

 is the radial sector. 



Redtenbacherf gives homologies of the wing veins of aphids 

 and psyllids, w^hich except for his interpretation of alternate 

 convex and concave veins, come pretty close to the conclusions 

 arrived at from the study of the tracheation. Except for Sc and 

 vein VI in the forewing and that Sc is not accounted for in the 

 hind wing his psyllid wrings are correct. His difficulties with the 

 aphid wings could not be settled without reference to the tra- 

 cheation. 



HandlirschJ gives the only figure of wing tracheae for psyllids 

 or aphids published previous to this present paper. His inter- 

 pretation of the tracheae for the wing pad of the psyllid nymph 

 is practically the same as that given in this paper. With the 

 freshly emerged wing of Schizoneura langigera, however, three mis- 

 takes occur. The line which he indicates as the subcostal tra- 

 chea does not occur as a trachea but as a well defined fold of the 

 subcostal vein. (See page 108). The unbranched trachea which 

 he considers M is really Cu. and his Cu. is one of the anals. The 

 question in regard to M. and Cu. however could only be settled 

 by the testimony of the tracheation of the wing pad. (See page 

 113 and fig. 21). 



* Oestlund, O. W. Aphididae of Minnesota, p. 4. 1887. 



Conistock, J. H. Introduction to Entomology, pp. 158-159. 1888. 

 t Redtenbacher, Josef. Ann. k. k. Naturh. Hofmus., I. 1886. 



t Handlirsch, Anton.' Die Fossilen Insekten und die Phylogenie der Rezen- 

 ten Formen. 1906-08. 



