In specimens of the two sexes from similar age groups of _hudsonius_ from Michigan, the mean values for each measurement for the two sexes differ only slightly or are essentially the same (see table 4). In no species has secondary sexual variation been found to be greater than individual variation.

TABLE 4.--Mean Measurements for Adult Male and Female Z. hudsonius of Age Group 2 and Per Cent Difference of Females to Males (Specimens from Michigan).

North American Jumping Mice (Genus Zapus) — Part 28

==============================+=========+=========+===================== | | | Per cent difference, Sex | Male | Female | females to males ------------------------------+---------+---------+--------------------- No. examined | 18 | 15 | | | | Total length | 202.85 | 202.88 | 0.02% larger | | | Hind foot | 122.85 | 122.10 | 0.60% smaller | | | Mastoid width | 10.10 | 10.28 | 1.50% larger | | | Occipitonasal length | 22.15 | 22.03 | 0.55% smaller | | | Incisors to postpalatal notch | 9.39 | 9.33 | 0.64% smaller | | | Zygomatic breadth | 10.47 | 10.57 | 0.95% larger | | | Maxillary tooth-row length | 3.52 | 3.60 | 0.23% larger ------------------------------+---------+---------+---------------------

North American Jumping Mice (Genus Zapus) — Part 28

CHECK-LIST OF THE SPECIES AND SUBSPECIES OF THE GENUS _ZAPUS_

North American Jumping Mice (Genus Zapus) — Part 28

_Zapus trinotatus_ 385 _Zapus trinotatus eureka_ A. B. Howell 389 _Zapus trinotatus montanus_ Merriam 390 _Zapus trinotatus orarius_ Preble 391 _Zapus trinotatus trinotatus_ Rhoads 392

_Zapus princeps_ 394 _Zapus princeps cinereus_ Hall 399 _Zapus princeps curtatus_ Hall 400 _Zapus princeps idahoensis_ Davis 401 _Zapus princeps kootenayensis_ Anderson 404 _Zapus princeps luteus_ Miller 406 _Zapus princeps minor_ Preble 407 _Zapus princeps oregonus_ Preble 409 _Zapus princeps pacificus_ Merriam 412 _Zapus princeps princeps_ Allen 414 _Zapus princeps saltator_ Allen 416 _Zapus princeps utahensis_ Hall 418

_Zapus hudsonius_ 420 _Zapus hudsonius acadicus_ (Dawson) 432 _Zapus hudsonius alascensis_ Merriam 435 _Zapus hudsonius americanus_ (Barton) 436 _Zapus hudsonius campestris_ Preble 441 _Zapus hudsonius canadensis_ (Davies) 442 _Zapus hudsonius hudsonius_ (Zimmerman) 443 _Zapus hudsonius intermedius_ Krutzsch 447 _Zapus hudsonius ladas_ Bangs 449 _Zapus hudsonius pallidus_ Cockrum and Baker 450 _Zapus hudsonius preblei_ Krutzsch 452 _Zapus hudsonius tenellus_ Merriam 453