Observations of prairie skippers (Oarisma poweshiek, Hesperia dacotae, H-ottoe, H-leonardus pawnee, and Atrytone arogos Iowa) (Lepidoptera : Hesperiidae) in Iowa, Minnesota, and North Dakota during 1988-1997

In transect butterfly surveys at 40 prairies in Iowa, Minnesota, and North Dakota in summer each year during 1988-1997, we recorded 2403 adults of Pow eshiek skipperling (Oarisma poweshiek) at 20 sites, 547 Dakota skippers (He speria dacotac) at 12 sites, 27 Ottoe skippers (H. ottoe) at one site, 290 Pawnee skippers (H. leonardus pawnee) at eight sites, and 81 Arogos skipper s (Atrytone arogos) at nine sites. In correlations of relative density (ind ividuals/km) of the analyzable species (all but Ottoe skipper), geographica l factors (latitude and longitude) produced the most significant correlatio ns, followed by timing (with higher numbers nearer noontime), and lastly we ather (positive correlation with temperature, negative correlation with win d speed). The relative densities of these analyzable species showed more si gnificant differences in relation to habitat factors than to variables desc ribing diurnal activity patterns or weather conditions. Relatively higher s kipper densities occurred in drier, undegraded prairie vegetation in sites with diverse rather than uniform topography. Patterns of relative density a lso varied among species with respect to management by idling, grazing, hay ing or burning. Nectar visits by species, and by sex if possible, are repor ted. More instances of courtship rejection than mating were observed. On la ter dates in the flight period, female Dakota skippers proportionately incr eased and the sex ratio became more variable. With increasing relative dens ity, the sex ratio of Dakota and Pawnee skippers became less variable and t ended toward values in the range of about an even ratio.