]^12 THE CANADIAN ENTOMOLOGIST 



in Fig. 3, nor is vein "R^" of Fig. 5 represented in Fig. 3. The differences be- 

 tween the two types of wings are very sHght, when one takes into consideration the 

 fact that they belong to insects grouped in separate orders, and the wing of the 

 Zorapteron shown in Fig. 3, is actually more like the Psocid shown in Fig. 5, 

 than this Psocid is like many other members of its own order of insects (the 

 Psocida). as one may readily see by comparing it with Cymatopsociis opalinus 

 and similar Psocids. At any rate, it is a comparatively simple matter to homol- 

 ogize the veins of the Zorapteron wing shown in Fig. 3, with the veins of the 

 Psocid wing shown in Fig. 5, and by working back to the intermediate type of 

 venation exhibited by the wing shown in Fig. 6, we have a connecting link pass- 

 ing over into the more typical venation of the order. 



Veins "R^ + s" and "R4 + 5" are distinct in the wing of Psyllipsocns ramburi 

 shown in Fig. 6; but in the hind wing of an aberrant form of this species, fig- 

 ured by Enderlein, 1903, these two veins have united almost completely ( they 

 are separate only near the margin of the wing, and for a very short distance) 

 which suggests that the vein labeled "R^+s'' in Fig. 5. represents the fusion pro- 

 duct of veins "R2+3" and "R4+ ■-" of Fig. 6. Similarly, the vein labeled "M2" in 

 Fig. 5, probably represents the fusion product of veins "Mi" and "M-" of Fig. 

 C), and the same holds true for the venation o' t"ie wing shown in Fig. 3, which 

 is homologous with the venation of the wing shown in Fig. 5. The discal cell 

 below the label "R^" in Fig. 5 is represented by a similar cell below the letter "R" 

 in Fig. C) (this cell has become obliterated in Fig. 3) ; but the longitudinal vein 

 "R4" of Fig. 5 has assumed a more vertical position in Fig. C), in which the vein 

 labeled "Ri" may represent only a portion of vein "Rj" of Fig. 5, or the latter 

 vein may have coaleced with the veins behind it, save for its terminal portion 

 which remains free to form the vein labeled "Ri" in Fig. 6. The \'ein "Cu^" of 

 Fig. 5, is evidently the homologue of the vein labeled "Cu^'' in Fig. 6, and it is 

 quite impossible that vein "Cui" has united with "Cu^" to form the single vein 

 labeled "Cu^" in both figures, although there is not positive evidence available to 

 determine this point ; and it is also quite possible that the vein labeled "Cu^"' re- 

 presents only the second branch of cubitus, the first branch (i.e. "Cui") having 

 faded out, or become lost in some such fashion. \Mien a wider series and more 

 intermediate forms of Psocids have been studied, these points may be determined 

 with more certainty, although an examination of the tracheation of the insects 

 in question would likewise throw mi^-h light upon the matter, if one could pro- 

 cure fresh material for study. These i)oints. however, are of minor importance, 

 and so far as the principal longitudinal veins are concerned, it is a comparatively 

 simple matter to determine their homologies in the Zoraptera and Psocids, the 

 only matter of uncertainty being to determine which of the branches of these 

 longitudinal veins are lost, or unite with other branches to form the terminal 

 portions of the longitudinal veins. 



The hind wing of the Aphid shown in Fig. 1 is rather suggestive of the 

 hind wing of the Zoraptera (Fig. 3 ) in its venation. The vein "Cu^" of Fig. 1, 

 however, is situated further (distally) from the base of the wing and is propor- 

 tionately much longer than vein "Cu/" of Fig. 3. and vein "R^. " is bent abruptly 

 forward in Fig. 3 while it extends more nearly in a 'Straight line with the basal 



