190 THE STUDY OF INSECTS. 
these legs were extended at right angles to the body like a 
pair of oars. The insect was unable to crawl up the vertical 
side of the aquarium, and after clinging to it for a short time 
it would lose its hold and sink back to the bottom. After 
watching it for a time I lifted it from the water by means of 
a stick. At this time its wings were in the form of pads, 
which were but little, if any, longer than the wing-pads of 
the pupa, as shown by the cast pupa-skin found floating on 
the water. The instant the creature was free from the water 
its wings expanded to their full size, and immediately it flew 
away several feet. In my efforts to catch the insect I found 
that it had perfect use of its wings, although they were so 
recently expanded. The time required for the insect to 
expands its wings and take its first flight was scarcely more 
than one second ; it was certainly less than two. As these 
insects normally emerge from rapidly-flowing streams which 
dash over rocks, it is evident that if much time were required 
for the wings to become fit for use, as is the case with most 
other insects, the wave succeeding that which swept one from 
the water would sweep it back again and destroy it. 
