430 



The observed maximum (27.8° C. ) is probably' not tlie real m^aximum 

 as no continuous series of summer temperatures was talven, and the diurnal 

 change in temperature was very great during the variable i>eriods of 

 autumn and spring. The greatest observed variation for twentj"-four hours 

 being 10° C. on Oct. 11-12. 



Temperature above 4° C. does not seem to affect the forms which are 

 found in the pond throughout the year, i. e., beetles, Corethra lar^^te, am- 

 phibian larvse, etc. Below this temperature, however, their activity is de- 

 creased and below 2° C. they are quite passive. For some time after the 

 ice foniied in the winter of 1909-1910, the Corethra larvse could be found 

 in all parts of the pond. Amphibian iarvjTe came to the surface when the 

 ice was cut, and the beetles could be seen crawling on the Tjqiha stems be- 

 neath the ice. On Jan. 11, 1910, the upper layers of water (three inches 

 under toe ice) had a temperature of 2.2° C. The lower layer (24 inches 

 under the ice) was 3.1° C. There were few Corethra larva; in the upper 

 layer and these were quite inactive. Near the bottom of the pond in the 

 deepest part, they were present in great numbers and were much more 

 active than those in the upper layers. Larvfe from either region became 

 more active when the temperature was raised. Many dead larva? were 

 found just below the ice. It may be concluded then that a temperature be- 

 low 4° C. reduces the activity of Corethra larva\ At 2° they become quite 

 passive and temperature lower than 2° may prove fatal. 



Amphibian larvae were active and could be captured in quantity during 

 December and most of January. On Feb. 1, 1910, the central, Typha free 

 part of the pond was carefully dredged for amphibian larvse but none were 

 captured. Holes were then cut in the ice nearer the margin of the pond. 

 Two larvse were captured ten feet from the north end. These Avere in the 

 debris among the Typha stems. They were rarely captured until the ice 

 disappeared in March. On March 3, the ice had disappeared and the larvjie 

 were much in ev idence. The temperature .iust under the ice on Feb. 1, was 

 .8° C. and near the bottom was 2.8. 



It seems that the formation of ice on tlie surface does not cause a 

 quiescent stage in amphibian larv£e but a temperature of about 2° C. does 

 reduce their activity. It may be, in both these cases, that it is the coit,- 

 tinued low temiierature that causes these stages of inactivity. However, 

 in the winter of 1908-1909, the water was not above 4° C. from Dec. 2 to 

 Jan. 27 and no period of inactivity was observed in these forms. 



