276 ECONOMIC MAMMALOGY 



been opened by mice, 3 per cent parasitized, 2 per cent destroyed by 

 fungi. 1 



Grasshopper mice 2 (Onychomys) during the summer live almost en- 

 tirely upon insects and other animal matter, but during the winter, 

 when their summer food is scarce, they will eat vegetables, seeds and 

 grain. They do but little harm and a great deal of good, killing and 

 eating pocket mice, field mice, deer mice and other destructive mice, 

 as well as large quantities of insects, mostly of harmful species. They 

 occasionally take lizards and amphibians. The contents of 96 stomachs 

 examined by Bailey and Sperry consisted of the following: Orthop- 

 tera, 38.76 per cent; Coleoptera, 20.73 P er cent; Lepidoptera, 17.04 

 per cent; Hymenoptera, 2 per cent; Diptera, 0.7 per cent; Hemiptera, 

 0.05 per cent; miscellaneous insects, arachnids and worms, 3.25 per 

 cent; mice, 3.09 per cent; grass seeds, 6 per cent; grain, 5 per cent; 

 unidentified, 6 per cent; total vegetable matter, 11.13 P er cent; total 

 animal matter, 88.87 P er cent (total insects, 78.28 per cent). 



Their food is chiefly "grasshoppers, crickets, beetles, moths, scor- 

 pions, spiders and any other mice or other animals that they can catch, 

 kill and eat. ... In the arid regions they take to some extent the place 

 of the moles and shrews of the humid regions in the destruction of 

 ground-dwelling insects and small animal life. In this respect they 

 may well be as useful as birds in helping to maintain a wholesome 

 balance of nature and in controlling the abundance of injurious forms 

 of life. The owl perhaps deserves no credit for swallowing these use- 

 ful little animals, and yet we cannot be sure that in unchecked abun- 

 dance even they might develop habits injurious rather than beneficial 

 to our interests." 3 



They also take some seeds, grain and vegetables. 4 "It would doubt- 

 less be possible to keep and breed them in confinement and make them 

 of use in ridding gardens and greenhouses of insect pests." 5 In the 

 Southwest, where scorpions are common, these mice are frequently 

 called scorpion mice, because of their fondness for the arachnids. 6 In 

 the case of the desert scorpion mouse (0. lencog aster fuliginosa), it 



1 Graham, The larch sawfly as an indicator of mouse abundance, Journ. Mam- 

 malogy, x, 189-196, 1929. 



2 Bailey and Sperry, Life history and habits of grasshopper mice (genus Ony- 

 chomys), U. S. Dept. Agric., Technical Bull., No. 145, 1929. 



8 Bailey, Animal life of Carlsbad Cavern, pp. 74-75, 1928; N. Amer. Fauna, No. 



25, PP- 93-94, 1905- 



4 Bailey, N. Amer. Fauna, No. 49, pp. 81, 83, 1926. Burnett, Office Colorado State 

 Entom. Circular No. 25, p. 7, 1918. Gary, N. Amer. Fauna, No. 33, p. 100, 1911. 



5 Bailey, Farmers' Bull., No. 335, p. 13, 1908. 



6 Gary, N. Amer. Fauna, No. 33, p. 100, 1911. 



