General Account of the Ithacan Aiiura. 



GENERAL ACCOUNT OF THE ITHACAN ANURA. 



THE FIRST APPEARANCE. 



When arranged according to their first appearance in the spring, 

 the eight species fall into five easily defined sections : (1) The peeper, the 

 meadow-frog, the wood-frog. (2) The toad, the pickerel-frog. (3) The 

 green-frog. (4) The tree-toad. (5) The bullfrog. 



The criteria of arrangement are: the earliest, latest, and average 

 dates of first emergence; the lowest and average maximum tempera- 

 tures* of the air; and the prevailing water- temperatures at the time and 

 place of appearance. This last factor can be applicable only to the 

 four species which hibernate beneath the water, namely : the meadow- 

 frog, the pickerel-frog, the green-frog, and the bullfrog. Some of the 

 pertinent data are given in the accompanying table: 



The first group of three (namely, the peeper, the meadow-frog, and 

 the wood-frog) forms a very distinct association. On the average, 

 they appear March 26 to 31. The intervals between the three succes- 

 sive appearances average two or three days and that between the first 

 and third averages five days. In the course of twelve years, all three 

 have first appeared on the same day but once; two of the three have 

 appeared on the same day in five different years. In these three we 

 can expect, in very early seasons, the appearance by March 19 or earlier 

 (sometimes two weeks earlier than the second group), and, in very late 

 seasons, the appearance at least by April 14. All three may emerge 

 under maximum air-temperatures as low as 41 to 45 degrees or under 

 average air-maxima from 50 to 53 degrees. In the meadow-frog the 

 water-temperature is the more potent factor of emergence and the 

 effective temperatures begin with 41 to 45 degrees and upward. 



The toad and the pickerel-frog follow soon after the first group. 

 They appear, on the average, from April 1 to 3, an interval of only 

 two days separating them. In very early springs, they may appear 



*A11 temperatures given in this study are in Fahrenheit. 



