Abstract The Poweshiek skipperling (Oarisma poweshiek) is endemic to the tall grass prairie in North America and is now critically endangered globally. Existing populations are scattered among tall grass prairie remnants. However, the host food plants eaten by Poweshiek skipperling larvae, the vegetative and microclimatic descriptions of immature and adult microhabitats, and O. poweshiek behaviour in Manitoba are unknown. We followed Poweshiek skipperling adults in their natural habitat to locate microhabitats where eggs were laid and to observe larval foraging behaviour and development. We measured vegetative, structural, and microclimatic characteristics of microhabitats used by immatures and documented the host species larvae consumed, their general behaviour (on plants; movement within microhabitats), and their developmental schedules. Larvae ate Andropogon gerardi, Muhlenbergia richardsonis, Sporobolus heterolepis, and Schizachyrium scoparium (all Poaceae) in natural tall grass prairie. Larvae appeared to navigate microhabitats to locate host food plants, alternating between shoots of various species throughout their development. Microhabitats seemed to be more open, with drier microclimates, than areas where eggs were not laid. This improved understanding of larval feeding patterns, adult behaviours, and microhabitat attributes may help local grassland stewards and researchers reduce the list of possible causes of decline and identify potential solutions to recover the Poweshiek skipperling.