370 
Psyche 
[December 
and the wing membrane between the veins is thickened and 
darkened. In Permohymen R1 is even more removed from 
the costa ; the pterostigmal cross-vein is only weakly 
formed, as a slight thickening of the apical edge of the 
pterostigma itself. The Doteridse have only a very feeble 
pterostigma; R1 is remote from the margin, and the area 
between is slightly darkened. In most specimens there is 
no pterostigmal cross-vein, but in other specimens of the 
same species there is a definite cross-vein here. The ptero- 
stigma in the Protohymenoptera is very primitive in struc- 
ture and does not, therefore, eliminate them from the 
Megasecoptera ; it is merely another slight specialization 
developed in connection with the reduction of the venation. 
Relationship with the Hymenoptera 
Now in demonstrating that the Protohymenoptera are 
megasecopterous we do not necessarily prove that they 
have no connection with the Hymenoptera. Only the word- 
ing of the question becomes slightly changed : were the 
Hymenoptera evolved from the Megasecoptera? If we 
attempt to derive the Hymenoptera in this way, we at once 
remove the order from all the other holometabolous in- 
sects, unless we postulate that they also originated from 
the Megasecoptera. The latter assumption hardly deserves 
consideration, for the Megasecoptera were far more 
specialized than the lower members of the panorpoid 
orders. The former proposition — that the Hymenoptera 
were evolved separately from the other holometabolous 
insects and developed complete metamorphosis indepen- 
dently — has already been offered by Tillyard (1926b). He 
says, “The fossil evidence is now fairly strong that there 
were three distinct groups of holometabolous insects which 
evolved a pupal stage independently of one another in the 
Permian period. These are (a) the Mecopteroid orders, 
namely, Mecoptera, Neuroptera, Paramecoptera, Para- 
trichoptera, Diptera, Trichoptera, Lepidoptera, and Sipha- 
naptera; (b) the Hymenopteroid orders, Protohymenoptera 
and Hymenoptera; and (c) the Coleopteroid orders, Proto- 
coleoptera, Coleoptera, and their parasitic offshoot, Strep- 
