102 K.\ TOMOLOC.ICAL NK\VS |. \\.\ii, '21 



scended from a common ancestry, which, from evidence drawn 

 from other sources, was apparently closely related to the 

 Zoraptera. In fact, the hind wing of one of the Aphid 

 Homoptera resembles the hind wing of a Zorapteron more 

 closely than any other insect I know of, and even in the fore 

 wings of the two groups (7. e., Aphids and Zoraptera) one can 

 find many points of resemblance, as one may see by com- 

 paring Fig. 5 with Fig. 4. 



The character of the thoracic sclerites of certain Psocida 

 indicates a close relationship to the Thysanoptera, as is also 

 true of the terminal abdominal structures of both sexes, and 

 I have even found a Psocid in which the head has begun to 

 take on the elongate form characteristic of the Thysanoptera. 

 The wing venation furnishes a brilliant confirmation of the 

 view that the Thysanoptera and Psocida are extremely closely 

 related, since the wing of the Psocid shown in Fig. 2 is more 

 like that of the Thysanopteron shown in Fig. 1, than it is 

 like the wing of other Psocids such as the one shown in Fig. 8 ; 

 and the study of the Psocids furnishes us with a ready solu- 

 tion of the difficult problem of determining the origin and 

 closest affinities of that aberrant group, the Thysanoptera, 

 which has so long puzzled the students of insect phylogeny; 

 and the study of the venation of the wings' of the Psocidae 

 also furnishes the key to proper interpretation of the Thysan- 

 opteron venation, which is still a matter of dispute. 



In both of the wings shown in Figs. 1 and 2, there are two 

 longitudinal veins extending almost parallel to each other down 

 the centre of the wing, while the only other veins present are 

 relegated to the small anal lobe at the base of the wing. The 

 veins of both wings are evidently completely homologous, and 

 by comparing the venation of the Psocid shown in Fig. 2 with 

 that of the Psocid shown in Fig. 8 it is a comparatively simple 

 matter to determine the homologies of the veins of Fig. 2, and 

 apply the interpretations thus determined, to the venation of 

 the wing shown in Fig. 1 . In the Psocid shown in Fig. 8, the 

 veins M+Cu, and M, if straightened out would assume the 

 position of the vein bearing the labels M+Cii and M in Fig. 2, 

 while the veins labeled R and Rs in Fig. 8, if straightened out, 



