1930 ] 
Geological History of Insects 
21 
dictyoptera, Megasecoptera, and the other extinct orders of 
the Upper Carboniferous, joining with this complex. 
If we examine a diagram showing the geological ranges 
of the larger existing orders of insects, we are at once im- 
pressed by the fact that ten of them have been found in the 
Permian ; of these, seven have been recognized in the Lower 
Permian, and one, the Blattids, in the Upper Carboniferous. 
These ten Permian orders are a rather diversified lot, in- 
cluding the Mecoptera, Neuroptera, Odonata, Homoptera, 
Psocoptera, Coleoptera, Diptera, Pleetoptera, Blattaria, and 
Orthoptera. Since their occurrence in the Permian marks 
the earliest record of all these insects, except the cock- 
roaches, let us see if these ancient representatives are as 
primitive as we might expect. 
The presence of Mecoptera in the Lower Permian is par- 
ticularly striking, inasmuch as our recent members of this 
order develop with complete metamorphosis. Of course 
since no larval or pupal forms of the Permian Mecoptera 
have been found, we have no direct evidence that they, too, 
were holometabolous ; but, as Tillyard has pointed out, they 
are so close to our existing types in other respects that no 
one would deny that they also possessed holometabolism. 
There are many features of these ancient scorpion-flies that 
are most unusual. Those from the Lower Permian of Kan- 
sas, with which we are best acquainted, are very minute, 
having an expanse of about 10 mm., — less than that of any 
existing species. Some of the Permian forms had short 
beaks, like those of the Australian Choristidae; the anten- 
nae were shortened and possessed fewer segments than 
those of any known Mecopteran except the highly special- 
ized Bittacidae; the males of some genera had a genital 
structure essentially like that of the Bittacidae, also. Fi- 
nally, some of the Lower Permian species had a wing vena- 
tion more highly specialized than that of any recent types. 
The Neuroptera have not yet been taken in the Lower 
Permian, but those of the Upper Permian were actually 
more specialized in their venation than their existing re- 
latives. Both the Planipennia and Megaloptera were al- 
ready differentiated and as highly developed along their 
own lines as the Mecoptera were along theirs. Although 
Tillyard maintains that the absence of Neuroptera in the 
Lower Permian collections is sufficient to show that the 
