Collectors and other observers have often noted that reptiles, in general, are not found in equal abundance throughout the entire season of their activity. Many kinds are most in evidence within a period of weeks after emergence from hibernation, which corresponds with the time of breeding and later they become much scarcer. In skinks of the genus _Eumeces_ this tendency is perhaps even more pronounced than in most other kinds of reptiles. By midsummer or considerably earlier their period of greatest activity is passed, and in some kinds, adults, or individuals of any size can rarely be found in the latter half of the growing season, even by a skilled collector familiar with their habitats and habits. Thus, Taylor (1936:5) in the preface of his revision of _Eumeces_, describing the difficulties involved in assembling needed series of the many Mexican species by collecting on summer field trips, wrote: "In 1934 in western Mexico ... I met with most disheartening results ... (although more than 1500 specimens were collected) only a single specimen of _Eumeces_ was taken. Hobart Smith, in 1934, accompanied by David Dunkle, made a journey into northwestern Mexico ... and while generally successful, likewise obtained only a single specimen of _Eumeces_." [Illustration: FIG. 7. Seasonal occurrence of five-lined skinks, based on data collected in 1949, 1950, 1951, and 1952; adult males and adult females are taken in greatest numbers in May, and in progressively smaller numbers through the summer and autumn; yearlings are found in increasing numbers through March, April, May, and June, then in decreasing numbers through the summer and autumn.] In the present study the tendency of _E. fasciatus_ to concentrate its surface activity in early spring was clearly shown. In unseasonably warm weather in early spring, even in February in one instance, individual skinks have been found active on the surface or beneath flat rocks warmed by the sun; but general emergence ordinarily does not occur until sometime in April, depending on the weather. Unless the weather is much warmer than the seasonal norm, the skinks spend much of April in a torpid condition, either not becoming fully active until late in the month, or lapsing into torpidity with the return of cool weather after their first emergence from hibernation. During warm periods in April, however, activity is at or near its annual maximum for all individuals regardless of sex or age.