MAMMALS 311 



because they are so fond of seeds, are very serious pests of 

 grain growers in many regions. The remedies for them are the 

 same as for gophers, that is, carbon bisulphide put into the holes 

 when the ground is moist, or poisoned grain put at the entrance 

 to the burrows. One of the western members of the group 

 has been found to be affected at times with the plague bacillus, 

 and instances are recorded where human beings have become 

 infected with this disease after being bitten by fleas from 

 plague-infected ground-squirrels. Some of the ground-squir- 

 rels compensate in a measure for the damage that they do, 

 by eating many destructive insects such as grasshoppers, 

 cut-worms, beetles, etc., often, too, killing mice and other 

 small noxious animals. The thirteen-lined spermophile, 

 Citellus tridecemilineatus , is common over the Mississippi 

 valley, and other large members of the same genus occur 

 throughout the West. The prairie-dogs, Cynomys ludovicianus, 

 are closely related to the ground-squirrels, and are found in 

 great "towns" over the western plains. Lands so infested 

 are unfit for cultivation and may even be ruined for pasture. 

 Wheat or other grain poisoned with strychnine placed at the 

 entrance to their burrows in the winter or early spring will 

 kill most of them. Carbon bisulphide, as recommended for 

 gophers and squirrels, is very effective. 



The shrews and moles belong to the order Insectivora, They 

 are all small carnivorous animals, which, because of their size, 

 confine their attacks chiefly to insects. The shrews are small 

 and mouse-like; certain kinds of them lead a semi-aquatic life. 

 There are nearly a score of species in North America. Of the 

 moles, of which there are but few species, the common mole, 

 Scalops aquaticus, is well known, while the star-nosed mole, 

 Condylura cristata, is recognizable by the peculiar rosette of 

 about twenty cartilaginous rays at the tip of its snout. Moles 

 live underground, and have the fore feet wide and shovel-like 

 for digging. As they destroy great numbers of cutworms, grubs 

 and other injurious insect larvae and do not eat vegetable food 

 they must be regarded as very beneficial. But their burrows 

 are sometimes so destructive in the lawns and flower beds that 



