252 THE CANADIAN ENTOMOLOGIST. 



segment. Segments of abdomen ventrally whitish with two 

 somewhat triangular-shaped brown areas on each segment as in 

 case of adult. The gills are of the typical Siphlonurus type. 

 See PI. X, fig. 11-15. Setae once banded beyond middle. 



This species is rather larger than 5. alternatus. It was found 

 emerging at Ithaca from June 5 to the 18th from a quiet spring-fed 

 pond. This pond was very much grown up with aquatic vegeta- 

 tion, especially Spirogyra, and many of the nymphs were covered 

 with colonial Vorticcllcp. 



Transformation. — The pond was about 40 ft. by 15 ft. with a 

 maximum depth of about 2 ft., but the greater part of it only 6 in, 

 or so. The water was very clear, so that the bottom could be seen 

 in many places through the vegetation. The nymphs could be seen 

 clambering about the water plants, swimming swiftly from place 

 to place by means of the very efficient tail tin and gill lamellse, or 

 quietly clinging to some object, while the gills moved in gently 

 undulating movements- and the abdomen swayed up and down. 

 Most of the nymphs were mature, and subimagos were continually 

 flying up from the pond. One mature nymph swam about with 

 its head up to the surface of the water as though looking for a 

 suitable place for em.ergence, going from plants, to dead leaves 

 and to twigs. It tried to climb upon a small twig, endeavouring 

 to hang on with its legs and bending its abdomen and setae around 

 in its attempts to get up on top. It was almost successful, but 

 suddenly abandoned the twig for a dead leaf. The leaf was only 

 partly submerged and the nymph climbed up over the edge and 

 up on top until only the abdomen was left in the water. Thus it 

 remained quietly for two minutes with its gills in constant motion. 

 It then crawled farther up the leaf until entirely out of the water, 

 and remained quietly for about 3 minutes, when the body, especially 

 the abdomen began to move convulsively, and in a couple of seconds 

 the thorax split and the body of the subimago gently slid out over 

 the surface of the leaf. When the legs were freed they were ex- 

 tended and at the same time the wings. Then the subimago took 

 a few steps, leaving only the setae still in the nymph slough. 



It remained on the leaf for about four minutes, moving its legs 

 and wings occasionally, and finally twisted and bent the abdomen 



