94 
Psyche 
IP 
simpler scheme comparable with that already suggested in the 
Homoptera by the Tillyard modification of the Comstock- 
Needham system The chief change concerns Cu. The vein 
formerly known by this name becomes Cm while the stem called 
by Comstock 1A + 2A is Cu2 + 1A. The corresponding change 
in Homopterous horismology has now been accepted by every 
authoritative worker in the sub-order while the present modi- 
fication seems to meet the approval of most of the Hymenopte- 
rists who have been able to examine the fossils. The differences 
in venation between Protohymenoptera and Hymenoptera may 
all be traced to specialisat on accompanying the evolution of a 
wing-coupling apparatus 
In spite of the fact that as far back as the upper Trias of 
Australia true Coleoptera were the dominant insects, the origin 
of the order long remained obscure. True beetles occurred also 
in the upper Permian and with them primitive forms resembling 
Coleoptera but with flattened elytra furnished with a straight 
sutural margin and complete venation. These insects, cons- 
tituting the new order, Protocoleoptera of Tillyard, were evidently 
nearly related to the ancestors of the Coleoptera, but their own 
affinities are very uncertain. 
Outside the Holometabola the Hemiptera (sens, lat.) have 
long formed perhaps the most isolated of insect orders. The 
Heteroptera truly recognisable as such are recorded first in the 
Triassic, where they were already differentiated into quite- 
specialised gymnocerate and cryptocerate types. Fossils con- 
necting this sub-order with more primitive forms are as yet 
unknown. With the Homoptera, however, the case is far 
different. Although the Protohemiptera, represented by Eugereon 
and by Mesotitan, are nothing at all to do with the Hemiptera, 
the Palaeohemiptera have proved so definitely hemipterous that 
they are now apportioned among various fossil and recent familes 
of auchenorrhynchous Homoptera. Most of the upper Permian 
Homoptera are distinctly either auchenorrhynchous or sterno- 
rrhynchous. Pincomhea is, however, in virtue especially of its 
well-developed clavus, possibly annectent, although predominant- 
ly sternorrhynchous. More generalised forms discovered in the 
lower Permian of Kansas have taken true Homoptera much 
