Adult phenology, relative abundance, and reproductive status of feral moths of the stalk borer, Papaipema nebris (Guenee), were investigated in Iowa, from 1980 to 1983, using collections from blacklight traps. Males constituted 89.2% of trap collections. In all 4 years the first moth was collected between 10 and 21 August and 50% flight occurred between 8 and 14 September. Multiple matings by female moths were common, with the mean number of spermatophores being 2.0, but total numbers ranging from 0 to 7 spermatophores per female. The mean number of spermatophores per female increased throughout the season to 3.0, suggesting that individual female moths are long lived. Although the dates of flights in this study agreed with Illinois dates, the thermal-unit model proposed in previous literature failed to predict satisfactorily adult phenology in Iowa, suggesting that factors other than centigrade degree-day accumulations influence adult stalk borer emergence and subsequent flights.