VB Davis 1935. Salmon Creek, 8 mi. W Rogerson, Twin Falls co, Idaho. May 15, Today we had high winds and rain in the afternoon and the sky remained overcast until after dark. As a result it got darker earlier than yesterday evening. I went down to the dam at 6:30 to await the arrival of the bats. I was interested to see what effect the daily fluctuation in intensity of light would have on their time of flight. Yesterday I saw 8:30 m.t. the first one at 7:30 P.M. (Pacific time) 8:15 m.t. Tonight I saw the first one at 7:15, indicating that intensity of light is a controlling factor. The flight tonight was very short as compared to the previous one. This is perhaps due to the cold; perhaps to cloudiness, but I believe it is the former. I was impressed by the fact that the Cliff Swallows were active, probably feeding, up to 7:10, then there was a lull of five minutes and the first bat appeared - a Myotis. Thus, there was no overlap in foraging times between the