50 
Psyche 
[March 
elusions has come from the study of Palaeozoic insects and more 
primitive groups of living insects with the result that the Lameere 
view has been generally accepted as a working hypothesis by stu- 
dents of fossil insects and insect evolution. In this connection, one 
should recall that Redtenbacher in his original account of vein 
homologies used the alternation of convexities as part of the evidence 
for his system of homologies. Unfortunately, the convexity or con- 
cavity of several veins has been lost in most orders of insects. The 
subcosta ( — ) , radius ( + ) , radial sector ( — ) , anterior cubitus ( + ) 
and posterior cubitus ( — ) tend to retain their topography in mem- 
branous wings, although virtually all veins in thick tegmina or elytra 
appear to have lost their topographic positions. The anterior media 
(■+) and posterior media ( — ) have generally come to lie flat in 
the wing membrane, except in the palaeopterous orders, where they 
are distinctly different. As a working hypothesis, I am assuming 
the presence of both of these veins in the early neopterous stock; 
there is some evidence from the pattern of these two veins in closely 
related taxa that they have been retained even in the endopterygote 
line (see, for example, Carpenter, 1940, Adams, 1958). Histological 
investigations on the development of convex and concave veins are 
still needed. Holdsworth included some histological observations in 
his work previously cited, but his studies were limited to one species. 
Mayfly wings, treated with caustic potash, separate into their orig- 
inal membranes, all the convex veins being on the dorsal membrane 
and all the concave veins on the ventral membrane (Speith, 1932; 
Holdsworth, 1941). Holdsworth noted that, although there was not 
this sharp difference in Pteronarcys , most of the cuticular material 
of the convex veins appeared to be formed in the dorsal epidermal 
layer and most of that of the concave veins in the lower epidermal 
layer. It is not improbable that this is generally the case. As noted 
above, veins have tended to lose the topographic characteristics in 
tegmina or elytra; and it is possible that a previously concave vein 
might eventually acquire a convex position secondarily if the tegmen 
became membranous. However, I regarded the latter occurrence as 
probably a rare event and consider convexities or concavities of veins 
as due to the original condition, unless strong evidence exists to the 
contrary. 
In my own work on insect evolution, therefore, I use the follow- 
ing terminology for wing veins : costa ( + ) , subcosta ( — ) , radius 
( + ), radial sector ( — ), anterior media ( + ), posterior media 
( — ) , anterior cubitus ( + ) , posterior cubitus ( — ) , and anals 
( + , — , or flat). The term postcubitus was suggested by Snodgrass 
