62 



Order INSECTIVORA 



Length measurements: head and body about 2l/^-2i/4 inches 

 (54-63 mm.); tail Yi-Ya inch (11-17 mm.); over-all about 

 lYz-^Y inches (65-80 mm.) ; hind foot ^ inch (9-11 mm.). 



The skull length is 16.0-17.0 mm. (about H inch) ; width, 

 7.5-8.2 mm. (slightly more than ^4 inch). The least shrew has 

 only two premolars on each side in the upper jaw, whereas all 

 other Illinois shrews have three. Part of the upper jaw is shown 

 in fig. 44/». Dental formula: I 3/1, C 1/1, Pm 2/1, M 3/3. 



Life History. — The least shrew often is found in old, weedy 

 fields, fig. 2, and thus it is sometimes called the old-field shrew. 

 It is frequently common in bluegrass meadows, occupying run- 

 ways of meadow mice. It may occur also in brushy, weedy, or 



Fig. 49. — Least shrew. 



marshy situations near woods but rarely, if ever, in forests. It 

 probably occupies burrow^s and runways made by various other 

 mammals, but some surface runs may represent paths made and 

 used exclusively by the least shrew. 



Except for Blarina hrevicauda, the least shrew is the com- 

 monest shrew in Illinois. In some fields, least shrews may be 

 as abundant as 10 or 15 per acre. 



It is not known when the least shrew breeds in Illinois, 

 when it brings forth young, or how many young are in each 

 litter. According to limited observations on this species in 

 other states, a litter may consist of five or six young. The com- 

 bined weights of these young while still nursing may be several 

 times that of the mother. 



Like other shrews, the least shrew has an insatiable appetite. 

 An individual kept in captivity ate seven migratory grasshop- 

 pers in 30 hours. It killed each one by biting the head, and then 

 it proceeded to eat the insect head first, discarding the wings 



