82 Journal New York Entomological Society. tvoi. xx. 



direct observation. Since most of the flies after maturity live on the 

 surface of the water, the eggs no doubt are dropped directly into 

 the water. 



Food Materials. — There is an alga in the lake everywhere common, 

 of the Nostoc group, its pulpy masses rolling up and down the beaches 

 with the waves, and often forming rotting deposits of horrible odor 

 along the upper beach as the level of the lake falls in summer. This 

 I take to be the food of gracilis and also of the brine shrimp, Artemia 

 fcrtilis, which are generally said to be the only forms of animal life 

 found in the waters. 



Habits of the Older Larvcc. — These seem to be suspended in the 

 waters everywhere, wriggling rather aimlessly, often hard to see 

 because of their half transparency. They do not show much dispo- 

 sition to keep near the surface ; I could see them at a depth of two 

 or three feet, which is as far as they could be made out on account 

 of their delicacy. The probably occur at greater depths. That they 

 do not come to the surface to breathe seems not to have been noted 

 in this or any other species before, but I feel confident of my pro- 

 longed observations on this point. The long tube and its filaments 

 must function as a tracheal gill, the spiracles at the tips being vestigial, 

 as the anterior pair of spiracles certainly are. The pup?e show close 

 to the anterior end the protuberant endings of a trachea on each side 

 (PI. VII, Fig. 7, shows the same in liiaiis) so that if these and the 

 posterior ones were functional we should have an amphipneustic 

 larva. The anterior spiracles, however, are more vestigial than the 

 posterior ones, and may be considered to have lost their function at 

 an earlier period. 



Puparia. — It is only in the pupal stage that the inconceivable 

 number of these flies present in the lake begins to make an impression 

 on the observer. The puparia are buoyant, regularly contain- 

 ing gas in the otherwise vacant space at the ends and around the 

 pupa ; moreover, they become attached to each other by the hardened 

 and somewhat recurved forks of the anal tube, so that vast masses 

 float along together. At Promontory Point I could see occasional 

 large brown patches of¥ shore, which I was assured were of this 

 nature, and I was told that they were continually drifting down the 

 Bear River Bay side of the Point, covering acres of water at a time 

 and six inches deep, one informant said (I think he said forty acres). 



