THE BIOLOGY OF THE RED-BACKED SALAMANDER. 337 



legs is similar to the sides. The eyes are large for the size of the 

 head, dark, iridescent, and very prominent. The nostrils are 

 visible; the head is quite flat, the nose rounded, not pointed. 



The skin is always moist and some amount of water is needed 

 in the environment, for a specimen kept in a dry pasteboard 

 box for a few hours was found in a much shriveled condition, 

 dead. 



The throat is in constant vibration which at times is very 

 rapid ; various counts were taken from seventy to one hundred 

 and eighty a minute. The costals or costal folds, from sixteen 

 to nineteen, are very easily seen. There seems to be no ex- 

 ternal character during fall and early spring to distinguish the 

 sexes; in a few specimens dissected, the males were larger than 



the females. 



ACTIVITIES. 



The red-backed salamander is almost entirely nocturnal. 

 Jordan and Kingsley mention this fact, while of Autodax lugubris 

 Hallow, which belongs to a genus close kin to Plethodon, Ritter 

 says it is entirely terrestrial and nocturnal. 



This salamander is quick of movement. Often when first 

 discovered, it is found in a graceful, curled position, and seldom 

 moves unless touched. If annoyed, it glides rapidly, sometimes 

 into crevices or holes and sometimes into the moss or leaves, 

 where it lies quietly hidden. In this rapid gliding movement, 

 the tail is lashed from side to side, as if aiding the fragile feet 

 and legs. 



It is a great climber individuals in the laboratory climb up 

 the sides of a glass vivarium with great ease, using the moist, 

 adhesive abdomen, as well as the feet and legs. They have 

 been seen to do this on rather dark days as well as in the evening. 



Kingsley mentions finding them out of doors on a "spear 

 of grass or coiled at the apex of a rachis of a fern at a distance 

 of from twelve to eighteen inches above ground." 



There is a peculiar jumping habit common to the species 

 if one is held in the hand, a foot or more above the moss floor 

 of a vivarium, it seems to gather itself together into a coil, and 

 using its tail as an aid, it springs lightly to the moss. The 

 whole process is indescribably quick. Kingsley says it "leaps 

 by sudden unbending of the coiled body like some caterpillars." 



