286 



THE WINGS OF APHID ID^ 



one anal trachea is present. The trachea of the radial sector is unbranched ; 

 that of media is only two-branched; and that of cubitus is not forked. 



In the wing of a newly emerged adult (Fig. 289) all the tracheae of the 

 cubito-anal group coalesce at the base of the wing. 



Fig. 289. — The tracheation of a freshly emerged adult Schizoneura 

 rileyi (After Patch). 



It should be observed that here, as is usually the case where there is a 

 transverse basal trachea, the medial trachea becomes a member of the 

 cubito-anal group. 



In two other cases the basal connections of the trachese are figured by 

 Miss Patch. Figure 290 represents the tracheation of the fore wing of a 

 newly emerged Aphis; and Figure 291 the tracheation of the hind wing of 

 a newly emerged Chaitophorus populicola. 



The data given above furnishes the key to an understanding of the 

 tracheation of the wings of Aphids. The two principal tracheae, which 

 extend from the base of the wing outward parallel to each other and to the 

 costal margin of the wing, represent respectively the costo-radial and the 



Fig. 290. — The tracheation of a fore wing of a newly emerged 

 Aphis (After Patch). 



cubito-anal groups of trachea. Of the former only the radial trachea is 

 preserved in this family; to the latter belong the medial as well as the cubi- 

 tal and anal tracheas. 



A comparison of Figure 292, which represents the wings of an adult 

 Schizoneura americana, will serve to show the relation of the tracheation of 



