314 MARY H. HINCKLEY, NOTES 



sylvatica, the wood frog, continue giving voice for a Avhile after the mercury had fallen to 

 30°. (Mr. Allen, in his notes on II. PlcTceringii, Proc. Boston Society Natural History, vol. 

 xn, p. 192, notes a similar occurrence at 31°.) Each occasion has followed a sunny day. 

 In one instance the temperature of the air during the day reached 48°; soon after the sun 

 went down it fell to 38°, while the water ahout the edge of the pond, where the frogs were 

 numerous, was 50-52°. As the air grew chill, light wreaths of vapor arose from the water 

 and were wafted over its surface, almost obscuring shore objects for a few feet above the 

 pond's level. Beneath this veil of mist the piping was at first vigorous, but the water grow- 

 ing colder the vapor gradually cleared ; at the same time the " peeps'' were fewer and 

 sounded slow and hoarse, as if given with a shiver, till at length the mercury filling below 

 30° the two or three frogs which appeared to have continued piping, in a spirit of rivalry 

 as to which could endure the greatest degree of cold, were chilled to silence. Morning 

 found a thin ice about the pond and thick hoar frost on the ground. 



In average seasons a few frogs may be heard about the 20th of March, but they are not 

 in full voice here much before the first week in April, about which date they collect in great 

 numbers for egg-laying in the shallow overflow of swamps, meadows, and ponds, the males 

 appearing in advance, and, as far as my observation goes, in excess always of the females ; 

 but even then their concerts are liable to be interrupted by brief periods of snow and freez- 

 ing weather when they disappear till the temperature changes again. The advent of an 

 east wind, to the sweep of which they are exjDosed, disturbs their piping, while the same 

 and even lower temperature with the wind in any other quarter is endured with apparent 

 indifference. 



While giving voice the frogs are not moving about in the water, but are partially or 

 wholly out of it, seated along the shallow edge amid dead leaves and grasses or clinging by 

 their sticking disks to the tawny, half-submerged weeds, small bushes, or reeds, where the 

 eye often fails to separate the frog from its surroundings, so perfect is the adaptation of 

 color and form; each curve of body and limb finding counterpart in bent grasses, dead her- 

 bage, and leaves. The frogs will be found of various shades of brown and capable of 

 changes within the limitations of that color; they do not, however, trust to the security of 

 this color protection with the stolid indifference of Hyla versicolor, the common tree toad. 

 The male frogs are a little smaller than the females of the same age and often darker in 

 tint. As is known, the latter sex has no external vocal sac and gives no note that I am 

 aware. The vocal sac of the male is largely developed in spring ; it is of a greenish 

 grey color and lies in loose folds outside the muscles of the throat. Inside the mouth are 

 two slits -or orifices, opening into the sac, one on each side near the angle of the jaws. 

 When the frog is about to give voice the whole body is inflated, followed by that of the 

 vocal sac which rounds out into a bubble and does not collapse with each " peep " ; the 

 degree of inflation evidently governs the volume of sound. About sunset 1 have frequently 

 been aided in discovering the frogs by the level rays of the sun striking along the edge of 

 pond or meadow and reflecting from this moist, inflated vocal sac with a glittering light. 



Unless the day is overcast, or a warm rain is falling, little is heard from the frogs till 

 about four o' clock in the afternoon when their concerts begin, to be continued in mild 

 nights till morning. Considering the size, the volume of sound possible from one frog is 

 surprising. As you approach a locality where they are in full voice the air seems to grow 



