l-RHQrENC:Y OF SliX CALLS 



a considerable inriuence of one indivitlual on another, the size of the congress, 

 therefore, having great influence on the calls. 



The data given for Microhyla c. olivacca shows almost exactly the same 

 tendencies as those for H. v. versicolor but these appear a little more clear-cut 

 because all records on rate happened to be obtained at the same air tempera- 

 ture (Table I, items 8, 9, and 10). The variation of 0.3 in the means when 

 water temperatures were also the same indicate a not quite perfect rhythm. 

 Comparing durations (Table VI, items 13, 15, and 16) and intervals, Table 

 VII, items 8, 9, and 1 1 ) in these same congresses, we see a greater variation 

 in the last two phenomena than in the first. Here again, the size of the con- 

 gress, with consequent effect of each individual on others present, is indicated 

 by general observation. 



The most adequate data have been secured on the three species of Pseud- 

 acris known in the Oklahoma fauna, Ps. clarl{ii, Ps. triseriata, and Ps. strec\- 

 eri. This is especially fortunate because it enables one to see more clearly the 

 difference in calling between these members of the same genus as well as to 

 elucidate further these ditierences in the closely related and often confused 

 forms c/ar^/V and triseriata. Data on numbers of calls per ten seconds observed 

 on 188 individuals of Ps. clar\ii, 278 of strec/{eri and 262 of triseriata are pre- 

 sented in Tables II, 111, and IV (cf. Bragg, 1948, Table II, for more data on 

 Ps. triseriata taken by this same method). 



In both Ps. clarion and Ps. streck^en the breeding call is so short a call 

 that durations and intervals are difTcult to obtain, and I have not included 

 any of my attempts in the tables because I have been uncertain of their ac- 

 curacy. The number of calls for unit time average rather high (14.6 for 

 clarkji, 20.5 for strecl{eri) and the variability is great in both ( R zn 5 — 33 for 

 clarf{ii, 8-50 for strecl{eri (Table II and III). However, if we omit the one 

 questionable series (Table III, item 11), the range in Ps. strecf(eri is from 

 8-30, making the two nearly comparable in variability. 



Both these forms call at low temperatures and I early noted that the call 

 of Ps. darken was slow at near freezing temperatures. I have not noted this 

 particularly in Ps. strecl{eri. But other factors are involved: (note Table II, 

 items 1 and 2). On the same date and within fifteen minutes of each other, 

 means of 12 and 8 were obtained in different congresses at the same tempera- 

 tures. While only six records were taken at the second of these congresses, I 

 could note no difference in the rhythm with considerable listening. To check, 

 I occasionally counted calls at random later while at the site and always got 

 eight per ten seconds. Item 3 is of interest also, because of special conditions. 

 The day had been bright and warm for the season after a heavy rain the day 

 before. At about 4:00 P.M. a cold wind bore down from the north, sending 

 temperatures down sharply. At 5:00 P.M. an almost constant rate of twenty 

 calls per ten seconds was recorded for a small congress of Ps. clarf{ii at the 

 edge of a terrace ditch. The falling air temperatures had not slowed the rate 

 of call against the still warm water. When both water and air are cold, how- 

 ever, (item 9) the rate seems to be affected markedly. 



With Ps. strecl{eri, two congresses on the same night varied by 4.8 calls 



119 



