I 



THE WINGS OF APHID ID^ 



287 



the wing to the definitive venation. This relation will be made more clear 

 by the following discussion of the separate veins. 



The costa. — A costal trachea was not found in any of the wings examined. 

 But Miss Patch observed that not only is the costal margin of the wing 

 stiffened by a vein-like structure, but this part of the wing contains what 

 appears to be a vein-cavity; as was shown by the fact that in severing the 



Fig. 291. — The tracheation of a hind wing of a newly emerged 

 Chaitophorus populicola (After Patch). 



wing from a freshly killed aphid, the yellow body fluids frequently flow into 

 this vein and extend along to about the region of the stigma (Fig. 290). 



The subcosia. — No subcostal trachea was found in any member of this 

 family. It may be that the subcostal vein is completely lost, or, as 

 Miss Patch concluded, this "is present in the large main vein channel of 

 the wing, and extends from the base of the wing to the stigma wh.re it 

 approaches the margin of 

 the wing." The lettering Sc*^R+M+Cu,+ lstA 

 of her figures is based on 

 this conclusion. 



The radius. — In the more 

 generalized members of the 

 family, as shown by the 

 figures given above, radius 

 is two-branched, in the fore 

 wings radius-one being pre- 

 served, and the radial sector 

 being unbranched. In the 

 hind wings, radius-one is 

 lost. 



In the Chermesinae, vein Ri is wanting in the fore wings as well as in 

 the hind wings. Figure 293 represents the tracheation of a fore wing of 

 Chermes abietis; Figure 294, the tracheation of a hind wing of Chermes 

 piniJolicB; and Figure 295, the definitive venation of both wings of a 

 Chermes. See note on page 291. 



A striking feature of the tracheation of the wings of Chermes is the 

 presence of many secondary branches of the tracheae. This feature was 

 observed in other genera also. 



Fig. 292 — The wings of Schizoneura 

 americana (After Patch) . 



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