THK HOUSE MOITSK, 



401 



Genus ]\Tus Linnaeus. 



Mus Liiiiicunis, Syst. Nat., ed. 10. {). 30, 1758. 



Dental Formula.— I, \Z\; C, "ll); Pm, jjl^; M, = 16. 



Generic characters. — Front teeth without grooves; molar teeth 

 with. tubercles of the crowns in three rows (these not evident in the 

 teeth of old animals, where th(^ crowns arc worn smooth) ; tail long, 

 scaly and scantily haired. 



Three species arc found in this State, all of which have been 

 introduced. The ii'cnus h;is a cosmopolitjui distribution and is rcf)- 

 resentcd by a very great number of species, chieHy in the tropical 

 regions of the old world. 



The Indiana species may be distinguished by the following key : 



Size small, under 200 mm. (S in.). M. musGulus. 



Size large, 300 mm. (12 in.) or more. 



Color bluish black; tail as lon^' or longer (lian the head and body; 



form slender. M. rattus. 



Color brownish; tail shorter than head and bndy; form rather stout. 



M. norvcgicus. 



MUS MUSl^TLUS Linnaeus. 

 HOUSE MOUSE. 



Mus musculus Linnaeus, Syst. Nat., ed. 10, p. 62, 1758. 



Evermann and Butler, Proc. Ind. Acad. Sci. for 1893, p. 127, 

 1894. 



Diagnostic churaiiers. — Size small (6 to 7 in.) ; color "mouse 

 gray," often with a tinge of yellow on the belly, but never with 

 bright brown back and white belly ; eyes and ears of moderate size ; 

 tail scantily haired and scaly ; skull small and delicate as compared 

 with the white-footed mouse. 



Range. — The house mouse probably came from Asia, but it is 

 now a household pest throughout the civilized world. It reached 

 America with the first colonists, and doubtless has lived in Indiana 

 almost from the time of the first permanent white settlements. 



Habits. — Not only are the house mice found in almost every 

 house and barn in the State, but they have also taken up their 

 abode in the fields. When the farmer takes up his shocks of grain 

 or fodder several species of mice are apt to scamper away, and 

 among them some house mice are very often seen. I have also 

 found them living in the open grassy fields in half a dozen coun- 

 ties. They no doubt go back and forth more or less between field 

 aud bari) and spend tlieii' time wherever they can most easily obtain 

 food. 



