RaTia septentrionalis 415 



The whole U. S. National Museum series shapes thus 29-40 or possibly 

 42.5 mm. transformation, average 37 mm.; 41 or 42-47 or 48 mm., average 

 43.5 mm. first year olds; 48.5-58 or 58.5 mm., average 53.5 mm. two year 

 olds; 60-72 mm., average 64 mm. three year olds. This material and ours 

 combined gives 29-40 mm., average 37 mm., mode 38 mm. at transformation; 

 40-48 or 50 mm., average 44 for ist year olds; 47 or 48 or 50 -58or 58.5 mm., 

 average 53.5 mm., mode 51 mm. for two year olds; and 59 or 60 to 72 mm., 

 average 63 mm., for three year olds. 



FOOD 



Garnier finds that (p. 945) "it preys on water beetles and similar insects, 

 but seems especially partial to the Julus family, having generally found it 

 in the stomachs examined." (P. 947) "the stomachs of many have been 

 examined by me, and they contained mostly Carabus, Julus, and water 

 insects, and on two occasions some little fish, chubs, if I remember correctly, 

 about an inch long. Thus their food is hke that of other frogs." In two dif- 

 ferent instances he found tadpoles eating dead fish, one a brook trout, the 

 other a chub. He saw one (tadpole) rush at, seize a large Ephemera that 

 came near it and swallowed it, yet it had not more than the third of its tail 

 absorbed." 



ENEMIES 



As already revealed under eggs the newt is a serious foe of the eggs and 

 hatching embryos. Being more common in the southern parts the water- 

 snake is a negligible factor in the life of this species unlike the case of R. 

 virgatipes. The great blue heron and other herodiones are amongst the worst 

 foes of the mink frog. 



AFFINITIES 



Garnier considered "certain peculiarities in the life history and in external 

 forms of these three Ranas {R. catesbeiana, R. clamaia and R. septentrionalis) 

 which so thoroughly agree that they may be separated into a group by them- 

 selves. These I shall endeavor to point out as concisely as possible:" 



"i . They have no 'chant amour' or love notes in spring. 



"2 . They retire early to hibernate with the first autumnal frosts. 



"3 . They live in water and lie in wait for their food, but do not hunt for 

 it on land. They poise the body on any floating weeds, lie on the 

 bank or any bit of stick or log that suits their purpose. 



"4. The tadpoles of R. catesbeiana and R. fontinalis require two years to 

 mature, and the mink frog requires the same period. 



"5. Adults in all three have no lateral fold, but merely a slight raising 

 of the skin from the angle of the mouth, and which terminates or 

 shades off on the shoulder. 



"6 . The foot is broader in proportion than in the rest of the family, and 

 the second toe is proportionately shorter, a peculiarity emphatically 

 distinct, and can be seen at an glance by any one who takes the trouble 

 of even a cursory observation, webbed to extremities. 



