79 
1947] Early Insect Life 
an aquatic life, with swimming legs, and the lateral ab- 
dominal gills. 
The other extinct Permian order is the Protelytroptera, 
which includes the most highly modified of all the Paleo- 
zoic insects. They had true elytra, very thick and convex, 
though with vestiges of venation (Figure 6). The hind 
wings were large, with a greatly expanded anal region, 
and with hinges on the longitudinal veins enabling the 
wing to fold up transversely as well as lengthwise. In 
Figure 6. Trot elytron permianum Tillyard (Order Protelytroptera), from 
the Lower Permian of Kansas. Original restoration, based upon specimens 
in the Museum of Comparative Zoology. 
general appearance these insects were highly suggestive 
of beetles, hut the venation of their hind wings shows 
clearly that they were not at all allied to the Coleoptera. 
They might be related to the roaches or to the Dermap- 
tera, hut most likely they represent an early and inde- 
pendent origin of the elytrophorous condition. Nothing 
is known yet of their mouthparts or of their immature 
stages. 
The foregoing discussion has dealt only with the extinct 
insect orders of the Upper Carboniferous and Permian 
periods. Let us now turn to the living orders. As we 
