394 CLARENCE HAMILTON KENNEDY. 



descend at a rate of several hundred feet to the mile. These 

 mountains are covered with pines on their high, dry ridges but 

 the deep ravines between these ribs of pine woods are filled with 

 a dense growth of deciduous timber so that the torrents are 

 heavily shaded by tall trees in their whole course. 



The burrowing larva of guttnlata lives in the meager areas of 

 coarse sand and muck found in the little basins below the water- 

 falls. The subimago emerges during the day. Those the writer 

 observed came out on dull cloudy days. These fly out of the 

 shade over the stream, through the surrounding brush and up to 

 the better lighted areas of the hill side where they rest in the 

 full light. The dull gray subimago then sheds a thin skin and 

 comes out a fully developed imago with its brilliant black and 

 white colors and its sexual maturity. No observations were 

 made as to whether this occurred on the day of emergence or 

 the following day. Because of the few subimagoes seen it prob- 

 ably occurred the same day as the emergence. Unfortunately 

 also, no mating dances were seen. These probably occurred 

 among the tree tops, in the deep dusk, just before egg laying 

 began. 



When the evening twilight had deepened to the point where 

 it became difficult to pick one's way along the streams, the 

 females of gnttulata would appear over the little pools hurrying 

 back and forth about a foot above the surface of the water 

 apparently laying eggs. Their conduct was more like that of 

 female dragonflies than like the usual hurried visit of the mayfly 

 female dropping all of her eggs in a single effort. No males 

 were caught at these times over the streams. 



It was in these flights in the dense twilight gloom of the bot- 

 toms of these mountain gorges that the probable value of the 

 bizarre coloration came to mind. The enormous development 

 of the eyes, the evidence of the rudimentary antennae together 

 with certain experimental work indicate that the major reactions 

 of the mayflies are through the sense of sight. Except for the 

 white abdomen, the mayflies, at the time of these twilight flights, 

 were practically invisible to the observer. These white abdo- 

 mens, as the guttnlata females doged about in the gathering 

 darkness, reminded one of the streaks of light of a flight of fire- 

 flies. Apparently then this white abdomen is useful to guttulata 



