1925] 
Storer: A Synopsis of the Amphibia of California 
257 
It may be that a certain limited percentage of the population lives 
on for a period beyond two years. In general, however, the environ- 
ment of this species, as indicated below, is ill suited to the continuance 
of large individuals or of any over a period of years. 
The food of boylii has not been investigated in detail. One indi- 
vidual collected near Covelo, Mendocino County, on July 19, 1913, 
was found to have its stomach crammed with grasshoppers. Boylii, 
in being active by day along stream courses, is probably able to make 
use of both aquatic and terrestrial insects, and it is probably able to 
get some provender at night as well. 
The life-history in relation to the environment. — Rana boylii 
boylii, the stream frog of central California, stands as a type distinct 
in habitat among the frogs of northern North America, Only its close 
southern relative (R. b. mnscosa) displays the same restriction of 
habitat. A parallel case is found with the ‘ tree-toad ’ of the southwest, 
Hyla arenicolor. 
As might be expected, the fortunes of the boylii population 
fluctuate with those of the stream. In its life-history boylii exhibits 
several striking specializations which are in all probability related to 
the requirements of life of a stream-dwelling species. 
Instead of the winter being the critical season in the life of this 
frog, it would seem that the summer months hold greater possibilities 
of danger for Rana boylii boylii. To explain the basis for this pre- 
sumption it will be necessary to discuss in some detail the annual 
cycle of a typical California foothill stream. 
In the first place, the greater amount of the rainfall in the foothill 
country comes during the late winter and early spring months. A 
lesser amount falls during the late spring and practically none during 
the summer season (see text fig. D). The slopes which form the 
drainage basin of a foothill stream are usually ill suited to retaining 
any great amount of the rainfall. The surface cover is chiefly of the 
dwarf forest or chaparral, with little or no leafy debris on the ground 
to serve as a spongy absorbent to hold the water as it falls. Conse- 
quently the run-off is extremely rapid ; a heavy rain is followed imme- 
diately by the swelling of the stream and much material is washed 
down the slopes and carried into the creek. At the end of the rainy 
season the stream rapidly subsides, and for a short period there is 
a moderate flow of clear water. The water, however, quickly lessens 
in amount, the stream becomes a series of pools connected by shallow 
