Fourteen of 20 females taken from the colony each carried a single embryo (crown-rump lengths measured 2 to 11 with a mean of 5.4). The other six were not visibly pregnant upon gross examination but had enlarged uteri, possibly indicating recent implantation. Of the remaining females from Harding County, three collected on May 29 had enlarged uteri, whereas two collected in late June evidenced no gross reproductive activity. A male obtained May 29 had testes that measured 4. Ectoparasites obtained from this species include chiggers, _Leptotrombidium myotis_ (Ewing), a tick, _Ornithodoros kelleyi_ Cooley and Kohls, fleas, _Myodopsylla gentilis_ Jordan and Rothschild and _M. insignis_ (Rothschild), and an unidentified species of mite. ~Myotis volans interior~ Miller, 1914 Long-legged Myotis _Specimens examined_ (43).--2 mi. N, 5 mi. W Ludlow, 4; NW 1/4 sec. 15, R. 5 E, T. 22 N, 12; 10 mi. S, 5 mi. W Reva, 27. The long-legged myotis is one of the commonest bats of the wooded buttes, accounting for almost half of all chiropterans taken in these areas. Most of our specimens were shot as they foraged among trees and over water in the evening; a few were captured in mist nets. Uteri of eight females obtained in the period May 23 to 31 were enlarged; two females collected on June 29 carried single embryos that measured 20 and 22. A lactating female was taken on August 3, but three other adult females taken early in the same month evidenced no reproductive activity. Testes measured 2 to 4 in three May-taken males and 4 in each of two from June. Two males obtained June 16 and 23 were molting as evidenced by new hairs under the old pelage over much of the body. _Myotis volans_ that we examined for ectoparasites harbored chiggers, _Leptotrombidium myotis_ (Ewing), and fleas, _Myodopsylla gentilis_ Jordan and Rothschild. ~Lasionycteris noctivagans~ (LeConte, 1831) Silver-haired Bat A single female, which contained two embryos that measured 4, represents the only record of a silver-haired bat from Harding County. This specimen was shot at dusk on June 1, 1968, as it foraged over a small pond in Deer Draw of the Slim Buttes (10 mi. S and 5 mi. W Reva). Several other bats believed to be of this species were seen at the same place that evening. We initially assumed that these were late migrants, but recent findings indicate that this species is a common summer inhabitant of the Long Pine Hills in adjacent Carter County, Montana, and likely, therefore, also a resident in favored sites in Harding County. ~Eptesicus fuscus pallidus~ Young, 1908 Big Brown Bat _Specimens examined_ (11).--NW 1/4 sec. 15, R. 5 E, T. 22 N, 3; 7 mi. N, 2 mi. W Camp Crook, 3300 ft., 2; 10 mi. S, 5 mi. W Reva, 6. The big brown bat is a common inhabitant of the Slim Buttes and North Cave Hills, where individuals were shot or netted as they foraged over water or among trees late in the evening.