496 



THE AMEBIC AN NATURALIST [Vol. LI 



that for Great Salt Lake water at the beginning of my observa- 

 tions, at which time the lake was in the rising period of its long 

 cycle of rise and fall, which rise continued at least up to 1915, 

 Some few years prior to 1909 the lake had been much lower and 

 the water at nearly the saturation point for NaCl. I believe 

 1.13 is somewhere near the mean density for Great Salt Lake. 



Interesting facts were noted concerning eggs contained in 

 dilutions made in autumn (see annual cycle below). These 

 hatched in a few days or weeks, and they first hatched in the 

 most dilute water, next in the next more concentrated, and so 

 on up the scale of concentration in nearly regular order. The 

 conclusion naturally presents itself that the stimulus to develop- 

 ment lies in the reduction in amount of salts present, but later 

 it appeared (this point was not finally cleared up) that it lay 

 rather in a lack of oxygen resulting from insufficient aeration of 

 the water used. Young thus hatched never reached maturitj^ 



Ephydra larvEe are even more abundant in the lake than Ar- 

 temias. They were found to be remarkably resistant to changes 

 in density of water, as well as to other changes in liquid environ- 

 ment. These larvae will live at least for days in tap water, but 

 whether they could be brought to maturity in this or in very 

 dilute lake water was not determined. The fact that the puparia 

 drift up on shore in great "windrows" has already been noted 

 by Aldrich,^ and in the Canadian Entomologist for 1891 (orig- 

 inal article not seen). The countless swarms of imagoes may 

 be seen by bathers resting on the surface of the water or flying 

 up at will, and it was found to be an easy matter to obtain the 

 eggs by imprisoning a number of these in a covered crystalliza- 

 tion dish with clean bottom, partly filled with brine, showing, 

 as suspected, that they drop the eggs freely into the water. As 

 this was not done until near the close of my service in Utah, no 

 experiments were made with the eggs, but attempts to hatch the 

 eggs and rear the insects to the imago stage in dilute lake water 

 and in fresh water should be made. As instances of the resist- 

 ance of these larvae may be mentioned the following: In more 

 than one case the larvae were observed to live months in brine 

 which had evaporated to saturation, and beyond to the point of 

 containing a heavy deposit of crystals and of being completely 

 encrusted on top, and in one such case practically all of the 

 water had disappeared. Among the salt crystals in the little 

 remaining water the larvae were somewhat inactive, but appeared, 

 to be in good condition when water to about the normal amount 



