ON THE PEEPING FRO«. 313 



the aid of a magnifying glass the upper surfaces of the body and the tail are seen to be over- 

 spread with a broken network of fine, deep brown, or black lines. The branchial cavity is 

 more or less pigmented with the colors of the upper surfaces ; the abdomen is silvery 

 white. Entering the fourth stage of Duges, which begins when the arms are thrown out 

 and ends with the resorption of the tail, the greenish sheen gradually disappears and the 

 skin develops the color and texture of the frog. Tadpoles of the same age vary in size, 

 even when grown under the same conditions ; when these are favorable, however, they 

 measure 30-33 mm. from tip of snout to that of tail, on reaching the limit of their size. 



Habits. 



H. Pickeringii is the most abundant of the frogs found in Milton, Mass. With E. syl- 

 vatica, the wood frog, it is the last species to become silent and retire from the surface in 

 autumn, and with that species responds eaidiest to the mild temperature of the variable 

 New England spring. The piping is not general, nor heard first at the water. The frogs 

 passing the winter in favorable situations on the land give voice earliest as well as con- 

 tinue it latest, for the notes of Pickering «', although most emphatic then, are not confined 

 to the mating season. In the first mild days when the mercury reaches 50° and 60°, days 

 that occur in some seasons as early as the last part of February, a few tremulous chirps, 

 given as if the frogs were not fully aroused from their winter torpor, come from the sunny, 

 southerly slopes of wooded hills where the same scattered voices presumably were last 

 heard in the autumn. In these warm nooks, protected from the north arid east winds, 

 snow and ice disappear first. The wet, flattened, and matted leaves soon become dry 

 and crisp, rustling with every breath of wind that stirs them. With the exception of 

 traces of snow, perhaps on the northerly slopes of the Blue Hills, and the overflow of the 

 meadows, the landscape is scarcely changed from what it was in the Indian summer days. 

 The signs of advancing vegetation are hardly perceptible ; there are the same browns 

 and neutral tints, softened by the haze of the south wind, and a like stillness in the wood 

 giving distinctness to any sound. Although Pickeringii may be heard on these days before 

 sylvatica has appeared in the swamps and ponds, observations of many seasons note the 

 latter species invariably collected at the water and egg-laying in the localities both fre- 

 quent, in advance of the former. As sylvatica gives a note less liable to attract attention, 

 the awakening of those individuals hibernating on land among the dead leaves is not so 

 promptly known as in the case of Pickeringii. With both species the time of appearance 

 varies with the temperature of the season. 



In 1880 Pickeringii was first heard here February 26, the temperature reaching 52° dur- 

 ing the day; while in 1883 they were not known to give voice till April 6, when the tem- 

 perature rose to 58°. In the year included from March 1879 to March 1880 they were 

 heard in Milton in each month of the year, excepting July and January ; but this was ex- 

 ceptional, owing to the unusual temperature of days in December and February when the 

 mercury ranged from 40° to 64°. I have no record of the frogs piping first in spring at a 

 temperature below 50° ; once called to the surface, however, they give voice at a much 

 lower degree, and, after collecting at the water I have twice heard them, together with 



