222 University of California Publications in Zoology [Vol. 27 
and so on. If a person walks out into a marsh where hylas are chorus- 
ing the notes quickly cease, ending usually with one or more of the 
single guttural notes described below. If the intruder remains quiet 
the hylas will usually resume after a few minutes, one individual 
beginning in a rather hesitating manner, then being joined by others 
one by one until the full chorus is under way once more. 
In areas of large extent such as the swamps adjacent to some of 
our main rivers, chorusing hylas may be scattered along for many 
miles. On the night of April 1, 1923, the writer traveled for several 
miles along the bank of the San Luis Rey River in San Diego County 
and all along the route there was such a chorus of hylas that it was 
impossible to hear any of the other night sounds. 
This hyla is to be heard mostly at night, the choruses beginning 
in the- late afternoon and early twilight hours, becoming stronger after 
full darkness has set in, and gradually dying away in the hours be- 
tween daybreak and sunrise. However, at the Thornhill pond, near 
Berkeley, during the months of J anuary to March, hyla choruses were 
to be heard at almost any hour of the day or night that the pond was 
visited. 
The ‘song’ season of Hyla regilla extends over a long period. As 
soon as rain pools are formed, in November or December, the males 
betake themselves to them and thenceforth nightly choruses are to be 
heard throughout the winter and spring months, up until April, and 
occasionally even later (for example, May 26, 1921, at Berkeley, and 
daily until June 9, 1924, at Davis). 
At any season of the year this hyla may be heard to utter a single 
prolonged note, kr-r-r-eck, lower in pitch than the song note. This 
note may be used, as indicated above, at the ending of a ‘ chorus ’ ; but 
it is also uttered in other seasons of the year when the individuals are 
hidden in their daytime retreats, and when no ‘ songs ’ are to be heard. 
The spawning season for Hyla regilla , taking its entire range into 
account, is as long or longer than that of any other species of western 
amphibian for which life-history data are available. In the lower 
altitudes of central and southern California spawning commences in 
January, provided sufficient rain has fallen to establish pools. In the 
neighborhood of Berkeley spawning extends from early January until 
the middle of May. The following table lists the available information 
concerning the spawning of this ubiquitous amphibian. 
