The Pacific Tree Frog 



(See Colour Plate IX.) Putting the frogs into a dark situation 

 again, they reverse the change, become vividly spotted, and finally 

 dark and unspotted. 



Any given collection of these tree frogs taken from the pond 

 will contain spotted specimens, unspotted dark and unspotted 

 light ones, and many in which the pattern shows obscurely. But 

 all will develop the typical pattern vividly if they are put under 

 the right conditions. Of the one hundred fifty specimens exam- 

 ined, no frog was found in which the pattern was wholly lacking, 

 though three out of the number had the pattern so reduced that 

 it consisted of a very small triangular patch between the eyes and 

 mere dashes of colour on the back. (See frogs in lower right- 

 hand corner of Colour Plate VIII.) 



The dark band through the ear and its continuation in dark 

 spots on the sides are constant factors in the colouration. The 

 only time that they are not visible is when the background is as 

 dark as the markings. 



Hyla regilla lives low, hopping about on the ground among 

 the blackberry vines and other vegetation, as does Hyla pick- 

 eringii of eastern North America. It is found especially about 

 springs, ponds, and moist places of all sorts. It calls from some 

 place of concealment in these situations on dark or rainy days and 

 at dusk. 1 1 may be heard occasionally throughout the winter, even. 

 In spring, it is to be found in great numbers in shallow pools. The 

 frogs then sing in chorus (especially at night), and a small number 

 of them can produce a noise so great that it sounds as though 

 made by thousands. 



The eggs are laid in February 1 and later. They are small 

 (i mm. diameter) and are in clusters of from twenty to fifty. The 

 clusters are attached to grasses and leaves in the shallow water. 

 (Fig. 167.) The tree frogs themselves may be found either in 

 the water or under stones and leaves nearby, depending on the 

 temperature of the day. 



Hyla regilla breeds in shallow ponds at Seattle, Washington, 

 in late February, at the same time that Rana pretiosa is laying its 

 eggs. The breeding-time begins earlier in southern California; 

 the metamorphosis may be completed in April. The young tree 

 frogs are small (J inch long), but show the typical pattern on the 



1 Feb. i2th, Carmel, Cal. L. S. Slevin, collector. 



137 



