THE CANADIAN ENTOMOLOGIST 113 



portion of the vein in Fig. 1. The fore wing of an Aphid (Fig. 7) however, is 

 more Hke that of a Psocid (Fig. 8) than that of a Zorapteron (Fig. 11 ). and the 

 nature of the veins A., and "Cu-:" of Fig. 8 is very suggestive of the condition ex- 

 hibited by these veins in Fig. 7. The incomplete vein "Rg" of Fig. 8 is also 

 very suggestive of vein "Rg" of Fig. 7; but the point of origin and the extent 

 of vein "M" of Fig. 8, is somewhat different from that of the vein bearing the 

 same label in Fig.7. On the whole, however, the resemblance between the types 

 of wings shown in Figs. 7 and 8 is very striking, and adds furtlier weight to the 

 evidence drawn from other sources indicating that the Psocids represent as nearly 

 as any living forms, the ancestral types from which the Aphids and other Hom- 

 opterous insects were derived. 



The venation of the fore wing of the Psocid shown in Fig. 2 approaches 

 remarkably closely the type of venation occurring in the Thysanoptera ;* and 

 since it furnishes us with the basis for determining the homologies of the Thy- 

 sanopteron venation, it is of considerable importance to make as accurate a de- 

 termination of the venation of the Psocid in question as it is possible to do from 

 the evidence at hand. A comparison of Embidotroctcs (Fig. 2) with Enibido. 

 psociis (Fig. 4) which is slightly less modified than the former insect, would in- 

 dicate that branch "R' -i- 2'' is either lost, or coalesces with "R* +»" (Fig. 4) to form 

 the terminal portion of the vein labeled "R " in Fig. 2. I am more incHned to con- 

 sider that vein "R2 + 3" of Fig. 4 is lost, in Fig. 2 ; and hence the terminal portion 

 of vein "R^" of Fig. 2 would be formed by "R< + 5" alone. The reason for so 

 thinking is that in the fossil Thysanopteron Palacothrips fossilis, the terminal 

 portion of a similar vein appears to be formed by "Rj -»-=", while vein "R2 + 3" be- 

 comes vertical, and takes on the appearance of a cross vein connecting it with 

 the anterior margin of the wing. This matter, however, will be discussed more 

 at length in a subsequent paper, and need not be further considered here. It 

 may be remarked in passing that the terminal portion of vein "M" of Figs. 2 and 

 4, is probably composed of "Mi", as is indicated by the labelling. 



The principal points brought out ip the preceeding discussion may be 

 briefly summarized as follows. The Psocids are much nearer the Zoraptera than 

 has formerly been supposed to bejhe case, and so far as the wing veins are con- 

 cerned, the Psocid family Caeciliidae approaches the Zoraptera much more close- 

 ly than any other known insects, the wings of the Psocid Archipsociis brasilianus 

 (Fig. 10) being remarkably like those of the Zorapteron Zorotypns siixdcri (Fig. 

 12) while the wings of the Psocid Archipsociis rccois (Fig. 9) are remarkably 

 like those of the Zorapteron Zorotypus, hubhardi (Fig. 11). In both groups of 

 insects there is a tendency to form a pterostigma "ps", and there is also a ten- 

 dency toward the formation ot a thickening of the margin of the wing to form 

 a sort of "ambient" vein like that found in the Thysanoptera. In both Zorap- 

 teron and Cfficiliid fore wings, the vein "R^x=" tends to curve forward toward 

 the anterior margin of the wing, and vein "M" is unbranched, and tends to bend 

 backward toward the jjosterior margin of the wing. \'ein "Cu" is two branch- 



* The veins labeled "M" and "Cu," in Fig. 3 of the fossil Thysanopteron described 

 in Ent. News Vol. 32, p. 97, should be labeled "Mi" and "M,". judging from the evidence 

 furnished by a study of the wings discussed in the present paper. 



