Mammals of Porter County 215 



The activities of these mice at night could be well inferred from 

 their footprints in the sand the following morning providing the night 

 had been still. Such footprints were well observed about our tent, and 

 about the fox grapes, red osier dogwood, and grasses, plants growing out 

 of clear sand. The usual mode of locomotion appeared to be a jump 

 using all four feet at once. The tail appeared to have been carried in 

 the air as no marks of it were left in the sand. The longest jumps were 

 from 10 to 12 inches, but usually they were much shorter being but 

 little more than the length of the animal. Only rarely did one find foot 

 impressions showing that the animals had been walking and sometimes, 

 in such cases, what appeared to be tail marks could be seen. 



Extreme and average measurements of ten adult males : total length 

 180, 172, 160; tail 82, 79, 75; hind foot 22, 21, 20 mm. Of ten adult 

 females: 187, 176, 172; 88, 80.5, 75; 21.5, 20.5, 20 mm. 



Between five and ten per cent of these mice captured were infested 

 in the inguinal region with a large fly larva, perhaps Cuterebra emascu- 

 lator. These larvae seemed well advanced in development, ranging be- 

 tween 10 and 15 mm. in length. Only one larva was found to a mouse. 

 On one occasion a particularly large larva emerged from its sac in a 

 dead mouse. The others remained within until removed in the process 

 of skinning. The majority of the mice infested were nursing females. 

 Only one was noticed in a male in which case the swelling caused by 

 the subcutaneous larva superficially resembled a swollen testicle. 



Baird, or prairie, deer mouse {Peromyscns vianicnlatns bairdii, 

 Hoy and Kennicott) : Eleven specimens of this mouse were secured, 

 nine being taken in the fore dune area amid Calamovilfa longifolia and 

 Primus pumila, and two in an intei'dunal meadow. The latter were 

 caught in traps set near holes that appeared to have been made by 

 crayfish. Besides the two captured in this meadow a third got into a 

 trap and left only its tail. None of the traps set in this meadow secured 

 Peromyscns leucopus noveboracensis or other mammals. With the ex- 

 ception of two house mice, the Baird deer mouse was the only mammal 

 taken in the fore dunes. Traps set at the top of a blowout about 150 

 feet above the lake and where much Calamovilfa was growing yielded 

 only the northern deer mouse. The Baird deer mouse does not appear to 

 be very common. On one occasion 80 traps were placed in the fore dune 

 area and not a specimen of any kind was secured and on another occa- 

 sion 78 traps were placed in the fore dunes and only two of this species 

 and a house mouse were secured. Hahn (4) did not find this species 

 very common in the state, recording it from only five counties. Ever- 

 mann and Clark (3) record three specimens fiom Lake Maxinkuckee 

 region and state: "It is very abundant in the sand dunes that border 

 Lake Michigan". 



What these mice do with themselves during the day, at least in the 

 fore dune region, is difficult to say, unless they dig down into the sand. 

 Only once I found what appeared to be a burrow. A trap placed near 

 it yielded nothing. As the habitat of these mice is much sandier than 

 that of the northern deer mouse their nightly activities were much more 

 visible. Judged by the large number of foot prints and the small number 



