BY R. J. TILLYAED. 419 



though, at the same time, it is evidently of much more archaic formation than 

 any type of Sternorrhyneha now known to exist. It is generally agreed that 

 the Psyllidae are the most archaic of the existing Sternon-hyncha. Text-fig. 4 

 shows the I'orewing of an unnamed Psyllid of comparatively large size (ex- 

 panse about 10 mm.) taken near Nelson, N.Z., which shows most of tlie archaic 

 venational characters for the family. By comparing this with the venation of 

 Lophioneura (Text-flg. 3) it will be seen that the following differences occur:-— 



(1) The Psyllid wing ha.s become broader and more rounded; and, con- 

 sequently, the costal margin has become strongly arched. 



(2) In the Psyllid, Sc is degrading, and fails to reach the costal margin. 

 (In some PsyUids, Sc is a short vein completely fused with the costa). 



(3) The primary vein formed of the fused bases of R, M and Cm is a 

 strong ridge-vein equally in the Psyllid as in Lophioneura; but the amount of 

 fusion of the three main stems which form it is much greater in the Psyllid, 

 and there is a further fusion of the main stems of M and Cui, after leaving 

 R; which is absent in Lophioneura. (In some Psyllids, however, this latter 

 fusion is absent. M and Cui leaving the primary vein at the same point). 



(4) The origin of Rs from Ri is placed much farther distad in the 

 Psyllid, while the main stem of R has become much shorter and turns up more 

 rapidly to join the costa. This last change is e-\-idently correlated with the 

 broadening of the wing. 



(5) The very evident tliickening of the costal margin in Lophioneura, 

 which begins at the end of R] and reaches almost to the apex, is present in 

 the same position in the PsyUid, but has become widened out into a coriaceous 

 stigmatic area, broadest at Ri. The ba.sal broadening of this area is again a 

 change that is dearly correlated with the broadening of the wing. 



(6) Rs has lost its fork. (If the position of the thickened costal area 

 is a guide, it would appear that this ha.s liappened by suppression of R 4-1.5). 



(7) M and Cui have retained their forks, but that of M has widened in 

 the Psyllid and altered in shape, while that of Cm has altered very little 

 indeed. 



(8) While the vein Cu2 -j- lA has altered little, the ai-eas above and below 

 it have broadened greatly. This again is clearly due to the general broadening 

 of the wing. 



I think that it will be admitted, from the above comparison, that the 

 Psyllidae may be considered, as far as their forewing venation is concerned, 

 to be direct descendants of the Lophioneuridae. Many autlioi-s have already 

 pointed out that the Sternorrhyneha cannot be derived from the Auchenorrhy- 

 neha, owing to their possessing several more archaic characters than tliese 

 latter. The Auehenorrh\nicl]a have already been found in existence in the 

 Newcastle Permian. We should naturally, then, expect to find the ancestors 

 of the Sternorrhynclia existing alongside tliem, though the probability of such 

 small wings being preserved is considerably less than in the case of the generally 

 much larger Auclienorrhyncha. Lophioneura may, I submit, ])e legitimately 

 considered to be a representative of this ancestral grou)"). 



From this same ancestral type, represented by Lophioneura, it is clear 

 that, as far a.s the forewing is concerned, the Aphiidae* can also he quite simply 

 derived, though in a different direction from the Pai/llidae. The line of evolu- 



• See A .C. Baker, "On the Family Name of the Plant Lice." Proc. Ent. See. Wash- 

 ington, xxiii., No. 5., May. 1921. pp. 101-lO.S. in which it is shown that the correct geni- 

 tive of aphis is aphios, not af>/iidos, and hence the family name should be Aphiidae , not 

 Aphididae. 



