ROD E N T I A 255 



forest fires, and thus they compensate for any damage they do. 33 Some 

 species, by destroying hordes of insects, to some extent offset the dam- 

 age done to crops, orchards and forests by rodents in general. "Ar- 

 boreal squirrels sometimes feed freely on scale insects and other tree 

 pests; the western ground squirrels eat quantities of injurious insects, 

 such as cutworms, wireworms and grasshoppers; and the so-called 

 grasshopper mice perhaps deserve their name and are undoubtedly 

 more highly insectivorous than the majority of their tribe." 34 The 

 insect-eating habits of rodents have been discussed in Chapter xxm, 

 on the Economic Relations of Mammals to Insects, and many addi- 

 tional items of interest along this line may be found under the various 

 species in subsequent pages. 



Some species of rodents are very useful because of their pelts, a 

 subject discussed in Chapter ix, on the Fur, Skin and Hide Trades, 

 with additional items under various species on subsequent pages. The 

 reported sales of rodent skins during 1919-1921, were as follows: 35 

 squirrel, 14,859,316; white hare, 3,713,036; muskrat, 14,109,288; nu- 

 tria, 1,941,784 ; chinchilla, 36,448 ; beaver, 420,490; marmot, 3,107,759. 

 In addition, it was estimated in 1921 that from 70,000,000 to 

 80,000,000 rabbit skins per annum are used. 36 The flesh of many species 

 of rodents is used as food and that of some species is sold in the mar- 

 kets. 



FAMILY SCIURIDAE SQUIRRELS, CHIPMUNKS, WOODCHUCKS, PRAIRIE-DOGS 



As we have seen, some species of squirrels are quite destructive 

 to crops. Though not carnivorous, some species are somewhat omniv- 

 orous, and it is well known that certain of them are more or less 

 destructive to the eggs and young of wild birds (see Chapter xx). 

 Squirrels and chipmunks eat many snails, 1 but in most regions this 

 does no harm, and in some localities it may do some good. Conchol- 



83 Hofmann, Furred forest planters, Scientific Monthly, xvi, 280-283, 1923. Mice 

 and chipmunks help restock forests, Journ. Mammalogy, n, 113, 1921, citing U. S. 

 Dept. Agric. Press Service. Shufeldt, Four-footed foresters, Amer. Forestry, xxvi, 

 37-44, 1920. Hatt, The relation of mammals to the Harvard Forest, Roosevelt Wild 

 Life Bull., v, 645-664, 1930. 



84 McAtee, The role of vertebrates in the control of insect pests, Ann. Rept. Smith- 

 sonian Inst. for 1925, p. 416. 



85 Osborn and Anthony, Journ. Mammalogy, m, 216, 1922 ; Natural History, xxn, 

 393, 1922. 



"Laut, The fur trade of America, p. 84, 1921. 



'Elrod, Univ. Montana Bull., No. 10, p. 114, 1902; The Nautilus, xvii, 4, 1903. 

 Van Hyning, The Nautilus, XVTII, 23, 1904. Howell, N. Amer. Fauna, No. 52, pp. 9- 

 11, 1929. 



