418 LIFE-HISTORY OF LESTES LED A SELYS, 



has unshaded gill-plates always; it is slightly larger than L. leda, 

 and the abdomen is seldom conspicuously marked as in the latter. 

 That of L. cingulatus is of a dull transparent brownish colour, 

 and every segment of the abdomen carries on either side of it, 

 near the anal end, a small hook bent backwards. It also has 

 unshaded gill-plates with fewer secondary tracheae than in L. leda, 

 and they are never bifurcated. 



Emergence of Imago. — For a week or more before emergence 

 the larva-nymph will cease feeding and turn gradually from 

 green to a dull brown, or sometimes to a rosy or even a blackish 

 hue. It will at times make violent rushes round the aquarium, 

 and often seizes upon some stalk and climbs vigorously up it, 

 only to rush as vigorously back again as soon as it has poked its 

 head out of water. This will go on until there arrives a warm 

 sunny day, when the nymph will at last ascend with a definit e 

 purpose. One of the nymphs which I had isolated in a small 

 glass jar provided with grass-stalks fortunately emerged on a day 

 when I was able to spend the whole time watching it (Aug. 13th, 

 1904). The morning was warmer than usual, and about 8a.m , 

 just as the sun's rays were beginning to slant in on the jar, the 

 larva-nymph became violently agitated and wriggled vigorously 

 about. Soon afterwards it seized upon a grass-stalk and climbed 

 slowly up it. Having got its head above water, it stopped to rest 

 about 5 minutes. Then it slowly ascended until it was two or 

 three inches out of the water. About this time I left for break- 

 fast, and on my return I found it had climbed up about two feet 

 on to some mosquito curtains, and was now full in the sun's rays. 

 Fixing its legs firmly into the meshes of the net, it now began a 

 series of internal struggles. In particular, it seemed to have the 

 power of extending its thorax by violent pulsations. Into the 

 extended thoracic cavity it next withdrew its head and legs, with 

 the result that, a few minutes after, it split open along the 

 dorsal ridge down to the wing-cases. Next, this opening was 

 enlarged by a transverse split across the shoulders. As soon as 

 this opening was sufficiently wide the insect withdrew its head 

 and forelegs from the shell, leaving its thorax partly protruding 



