[Illustration: Fig. 4. Geographic distribution of _Eumeces inexpectatus_, as indicated by published records; only marginal and near-marginal records are shown, excluding those of doubtful validity.] Under present conditions, with these three species so similar in habits and so extensively overlapping in geographic range, it is difficult to visualize a barrier such as would have been required for allopatric speciation of the type, usual in vertebrates, to have occurred. One might be tempted to postulate sympatric speciation, with the parent form, presumably _fasciatus_, giving rise to the other two by abrupt mutations. However, the demonstrable antiquity of the five-lined skinks would allow ample time for divergence, allopatric speciation, and subsequent disappearance of the barrier and intermingling of populations. The displacement of floras and faunas that occurred in the Pleistocene, with the successive advances and retreats of the continental ice sheets might have had some part in bringing about the present overlapping distribution, after the disappearance of the original barrier. Such a barrier might have been an eastward extension of the central grasslands to the Atlantic Coast at a time when the climate of the continent was warmer and drier. [Illustration: Fig. 5. Geographic distribution of _Eumeces laticeps_, as indicated by published records; only marginal and near-marginal records are shown, excluding those of doubtful validity.] Habitat and Limiting Factors TEMPERATURE AND MOISTURE RELATIONS For approximately half the year, at the latitude of northeastern Kansas, five-lined skinks are dormant. In early fall, even before the advent of cold weather, they are hard to find apparently having begun their retirement into the sheltered situations where they spend the winter, even though they may not be fully dormant at that time.