Diurnal activity and territorial behavior of the tiger beetle, Pseudoxycheila tarsalis Bates (Carabidae: Cicindelinae), were studied in San Vito, Costa Rica, by marking the beetles, observing their behavior and distribution, and timing their activities. We tested hypotheses that: 1) beetles were randomly distributed in the study area, 2) male and female beetles moved equally throughout the study area in one day, and 3) males and females moved the same distance over successive days. Beetle activity increased with increasing temperature and decreased with cool, rainy, or cloudy conditions. The beetles preferred open areas with no vegetation. Males drove away other males that entered their “territory” where they rested and attempted to copulate with passing females. Both sexes of P. tarsalis showed some fidelity to an area, but males ranged only about half as far as females. Males may derive a reproductive advantage by restricting their range and waiting for receptive females, even those ovipositing. Individuals of both sexes returned to approximately the same general area after their daily foraging, ovipositing, and other activities. Individuals were normally (Poisson) distributed throughout the study area, with about eight beetles per 4 × 5-m plot at any one time.