The life history and critical requirements of the scarce prairie-obligate skippers Hesperia dacotae and H. ottoe and mortality during prescribed fire in spring were investigated during 1978-83 at a site in southwest Minnesota. Both species are univoltine, flying together at this site in early to mid-summer. No differences between the two in habitat use were apparent and adults spent almost all of their time in the same upland prairie where larval development occurred. Larvae of both feed on most of the grasses in this habitat, and females of both oviposit without apparent selectivity on grasses as well as on forbs. Both have the solitary, shelter dwelling larval habits of the genus. Shelters of H. dacotae are subsurface, burrow-like chambers until after the first postdiapause molt in spring, and then debris covered silk chambers on the surface. Habits of H. ottoe are identical from late summer on, but early stages make shelters up in the grass blades. These behavioral programs appear to be functional only in midheight, bunchgrass dominated vegetation. Both sexes are frequent flower visitors, water probably being the critical need.Potential fecundity in both species appears to be approximately 200 eggs, which are matured at a declining rate over a three week life span. A three year mark-release-recapture study of adults yielded estimates of average residence time within the site of between three and six days far males, and between three and ten days for females, in both species. Hesperia dacotae was the more abundant during the study, with annual cohorts estimated to be between 2,000 and 3,000 adults, compared with estimates between 600 and 1,200 for H. ottoe. Estimates for females were consistently lower than for males.No difference between the species in the effects of spring burning in prairie plots was detectable. Fuel load strongly influenced mortality. Compared with unburned controls, mean survival in low-fuel plots was reduced 11% in the early spring burn when larvae were still in burrows, and 26% in the later burn when larvae were in surface shelters. The respective reductions in moderate-fuel plots were 78% and 100%. The fuel loads of 160 and 540 gm-² approximate natural extremes for the larval habitat. Although the higher mortality in the later burn is not statistically significant, further investigation of the effect of date of burn is recommended. Management implications of these results are discussed. © Minnesota Agricultural Experiment Station. University of Minnesota. Abstract reproduced by permission.