The Tree-toad, Hyla versicolor LeConte. 45 



From the nature of the places in which tree-toads are first found, air- 

 temperature must be the influencing factor of first appearance. Some- 

 times, while scuffling along through the dead leaves of the woods, one 

 happens upon them. We have found them on tombstones in a wooded 

 cemetery; on a high hill some 50 to 75 feet above the pond they will 

 finally reach ; in large trees, and even on our back porch. The maximum 

 air-temperatures for the first appearance of each year give an average 

 of 70 degrees for the day of the record, and 66 degrees for the day pre- 

 vious. Every record with one exception is flanked on one side by a 

 temperature of 70 degrees or more; and no record (one exception) 

 descends below 58 degrees, which appears in four different instances. 



THE VOICE. 



The tree-toad so imitates its environment that it is best known by 

 its voice. In fact, previous to 1906 our first appearances were based 

 upon such records. In 1906 one day intervened between first appear- 

 ance and the first note of the tree-toad, the ruling temperature being 

 71 degrees; in 1907 the interval was prolonged by cold weather (May 

 1 to 12, average maximum temperature 50 degrees; average minimum 

 temperature 36 degrees), and the first warm day (May 13) immediately 

 brought the males into voice; in 1909 two days passed at 10 and 8 

 degrees lower than 71 degrees, the temperature at which they finally 

 began. An average of 20 air-temperatures taken at the moment 

 of voice-record yields 69 degrees with no individual records below 

 61 degrees; an average of the Weather Bureau maxima for the days of 

 first voice-records, from 1901 onward, gives 72 degrees with no indi- 

 vidual record below 64 degrees. Hence, it is safe to conclude that 61 

 degrees is the minimum and 70 degrees the average effective heat. 

 At the breeding season their loud resonant trills begin in late afternoon 

 and continue sometimes long beyond midnight. Occasionally, a few 

 trills will begin in midafternoon, the customary period being from 4 to 

 8 p. m. By the latter hour the chorus is well started. When at the 

 height of their breeding and usually after a warm rain or during an 

 overcast sky they may be heard at noon or before, the earliest in the day 

 being 10 a. m. Rarely, stray individuals may be heard before noon or 

 shortly after, even though no rain precedes or clouds are present. 



About the middle of May, they are in the chorus stage. At Ithaca 

 in the evening, all over the university hill and the hills nearby, along the 

 wooded ravines, in the thickety edges and woods of our marshes, and 

 on the campus itself at our very door, we may stumble upon the noisy 

 tree-toads slowly approaching the nearest breeding-place. In one 

 instance their resort is a pond at the end of a long hedge. Here, at the 

 breeding season, every evening and sometimes after a thunder-shower 

 by day, the males can be heard all along its length, slowly bound for 

 the one objective pool, where some have already arrived. 



