J42 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



instance an adult female and a half-grown young individual 

 were taken from the last double handful of the nest-mass 

 remaining in the tree. 



The tree mice when caught did not ordinarily defend them- 

 selves with energy, although one young individual seized a 

 finger of its captor and bit hard enough to draw blood. 



5 VOICE 



Wilder asserts that when individuals of Phenacomys longi- 

 caudus are caught they utter a mouse-like squeak. Only one 

 of those taken by us was heard to utter a sound. This was a 

 juvenile individual which, upon being seized, squeaked plain- 

 tively. 



6 FOOD AND DRINK 



At Mendocino City we always found green twigs on and 

 in occupied nests. The leaf of a grand fir was found in the 

 mouth of one individual, and the stomachs and intestines of 

 all those examined were brilliant green. Microscopic examina- 

 tion of cross-sections of the fir needles discloses the fact that 

 all the fleshy substance of the needle including the vascular 

 bundles is eaten away by the tree mouse, the only portions left 

 being the two resin ducts which traverse the entire length of 

 each needle. These filamentous resin ducts have quite natur- 

 ally been mistaken for midribs by some observers. The outer 

 or cortical portions of young shoots are also used as food, in 

 this case resin ducts and all being eaten. It is probable that 

 the chief food of the species is derived from the needles and 

 young shoots. 



In a colony on Chaparral Mountain, on the slope above 

 Maplecreek Postoflice, Humboldt County, California, which 

 was studied by Clay, the top of practically every inhabited 

 tree was dead. Many nests were found by locating the dead- 

 topped trees. "The nest was sure to be there," says Clay, 

 "and was always inhabited." In some cases in which the nest 

 was low in the crown of the tree and far out on a limb, the 

 bark would not be touched, but in the dead-topped trees small 

 runway-like trails were noticed over the trunk where the 

 bark had been stripped away. Sometimes these trails ran 

 together making a wide exposed place. The tree was cut 



