iiS An7ials Entomological Society of America [Vol.11, 



disappeared as is frequently the case.* The subcostal and sec- 

 ond anal tracheae have migrated to very near their respective 

 margins of the wing, but are both distinct. The first anal, a 

 slender but distinct trachea, follows the course of the claval su- 

 ture. The proximal portions of the radial, medial and cubital 

 tracheae are coalesced into a common stem at the basal fourth of 

 the wing. This main stem divides into two tracheas, the radial 

 and the common stem of the medial and cubital . The latter soon 

 separates again into the free portions of the medial and cubital 

 tracheae. 



There is a greater degree of coalescence in the tracheation of 

 this psyllidwing than occurs in that of the aphid wing as the 

 radial trachea is always (except in very unusual variations as 

 cited, page 107) separate to the base of the freshly emerged aphid 

 wing. 



The venation of Psylla floccosa (fig. 36) coincides with the 

 tracheation of the freshly emerged wing very closely. Subcosta 

 strengthens with the costa the cephalic margin of the wing. The 

 second anal in a similar way reinforces the anal margin at the 

 base. The first anal is so delicately traced along the claval suture 

 that it cannot function as a strengthening rod in the wing as do 

 the other veins. Indeed it has frequently been considered not a 

 true vein. 



Radius, media, and cubitus share about equally the burden of 

 strengthening the wing. They are coalesced as a common main 

 stem at the base. The relation of media and cubitus is similar 

 to that of the same veins in the wing of the aphids and this typi- 

 cal two branched cubitus bears further evidence of the correctness 

 of the interpretation of cubitus in the aphid wing. 



Ri responds to the mechanical necessity for strengthening the 

 front of the wing. It is the only vein present in this region and 

 upon it falls the burden as well as the approximate position usually 

 assumed by the subcosta in many insect wings. Rs is a strong 

 vein and reaches the margin near the apex of the wing. 



The tracheation of the freshly emerged hind wing of Psylla 

 floccosa resembles that of the front wing closely. (Fig. 35). 

 The subcostal and second anal tracheae lie near their respective 

 wing margins, as in the front wing. The first anal trachea occu- 



* "Its trachea is often atrophied, probably owing to the disadvantageous 

 position of its base in relation to air supply, as we have hitherto indicated." 

 Comstock-Needham: Wings of Insects, page 858. 



