Quimby (1951:74) frequently found the fleas, _Megabothris quirini_ Rothschild, and _Megabothris wagneri_ (Baker), and occasionally a larval tick, _Dermocenter variabilis_ (Say), on _Z. hudsonius_. Sheldon (1934:296) remarks that captive animals are burdened with numerous fleas. Hamilton (1935:191) removed a louse from a jumping mouse. One mouse had a hole in the throat and three others had holes in the inguinal region; presumably bot-flies had emerged from these holes. Test (1943:507) found a single _Cuterebra_ larva in the inguinal region of a _Z. hudsonius_, and Sheldon (1938:328) found _Z. hudsonius_ infested by larvae of _Cuterebra fontinella_ Clark. Here, as in other cases, these larvae were found immediately below the skin. Erickson (1938:252) examined 18 _Z. hudsonius_ obtained in Minnesota, and found that three were parasitized. He found a bot-fly larva, _Cuterebra_ sp., nematodes of the genera _Subulura_ and _Spirocerca_, and a fluke of the genus _Notocotylus_.
_Food._--Quimby (1951:85-86) studied the food preferences, by presenting to caged _Z. hudsonius_ the plants and invertebrate animals normally available to these mice in nature, and indicates that in general, the starchy fruits of the Gramineae and the less fleshy fruits of various groups of plants are more heavily utilized than other plant materials. His observations indicate that these rodents are highly insectivorous and that they consume many insects under natural conditions. Goodwin (1935:148) reports that the stomach contents of several individuals obtained at South Woodstock, Connecticut, consisted exclusively of blackberries, and that others had subsisted principally on cranberries. Hamilton (1935:197) remarks that seeds are the favored food but that berries, nuts, fruits of various kinds, roots, and insects are also utilized. Stoner (1918:123) writes that the food in cultivated areas of Iowa is various grains as well as grass and weed seeds; in wooded places the mice feed on seeds and nuts of trees. Vernon Bailey (1927:118) states that the examination of a great many stomachs of these jumping mice [in North Dakota] revealed nothing "but the fine white pulp of carefully shelled, well-masticated seeds. Generally these are from grasses, although grain and a variety of other plant seeds are eaten." Schmidt (1931:116) examined the stomach contents of several _Z. hudsonius_ taken in Clark County, Wisconsin, and in most stomachs found the remains of finely chewed roots; however, two from Hewett had eaten several geometrid caterpillars.