No. 488] 



HABITS OF THE SHREW 



519 



of Blarina. In other situations than the j)eaty swamp, the earth- 

 worm diet is probably greater than I have estimated. In pro- 

 portion as other foods not liere included are empkned, the 

 quantities in the table will be diminished. 



Table IV. Showing estimated quantities of various staple foods devoured 



Meadow voles (or equivalent in mice) 

 Adult insects (of the size of Lachnosteri 



Estimating the number of shrews as I have done at four per 

 acre, it appears that the number of meadow voles devoured bv 

 them on a farm of 100 acres in a year is 100 X 4 X 12 X 8 =?,Sm. 

 Since this number can scarcely be supplied, the capacity of the 

 shrews for keeping the voles in check is not strained. Where 

 this quantity of voles can not be found, either other foods nnist 

 be eaten in equivalent amounts, or the shrew is capable of sub- 

 sisting on shorter rations, or the estimated four shrews ]X'r acre 



a year than the f;ivnuM- himself. The shrew even compare; 

 favorably, IVoin iUc (•(OM..iiiic standpoint, with the common owls 

 Montgomery i ls!)!i i t'xaiiiiiu'd the pellets of four long-eared owl; 

 for a peri...l of tuo inonTh^. and found that these birds had de 

 vonred ;U7 .mall niamn.aK. mosilv Microtus. This is an average 

 of l:! per mo.ith for each owh " Blarina devours 20 voles pei 



