MAMMALIA. 313 
obtaining food. They are found near streams and moist 
spots. The common mole (Scalops aguaticus, Linn.) (Fig. 
339) leaves its 
traces in up- 
turned ridges in 
every field of 
the Eastern 
States. They 
attain a length 
of five inches. 
The fore-feet 
are greatly de- 
veloped for 
digging ; _ their 
eyes are com- 
paratively use- ry, 338.—Star-nosed mole (Condylura cristata) : 
less, being ex- a, jaws ; 4, end of nose. 
tremely small,* 
giving rise to the impression that they are eyeless. Their 
nests are underground, and their principal food earth- 
worms. 
Allied are the Solenodon of Hayti and the Tanrec of 
Madagascar. 
VALUE.—Fur, and as insect-destroyers. A single mole is estimated 
to eat 20,000 insects in a year. One has been known to devour 432 
maggots and 250 grubs in four days ; another ate 872 maggots and 540 
grubs in twelve days. In another instance two moles in nine days de- 
voured 341 grubs, 193 earth-worms, 25 caterpillars, and a mouse, its 
bones and skin, : 
* The eyes are deeply imbedded, but are perfect, the lens consist- 
ing of a very small number of minute and little altered embryonic 
cells, The retina is more simple than generally seen in other ver- 
tebrates. In the embryo mole both eyes are connected with the 
brain by optic nerves, but in adults the optic nerve has degenerated, 
sometimes one and again both, so that, though the image may be 
possibly formed in the eye, it is with difficulty communicated to the 
brain. 
