Seven species of Onagraceae, Tribe Onagreae, occur at sites in Konza Prairie Research Natural Area and Tuttle Creek Reservoir Dam area, controlled by the Kansas Army Corp of Engineers. Three species bloom in the Spring and four species bloom from mid-Summer into Fall. The Spring group displays flowers in an unstratified pattern with fewer, but larger, flowers per stem per day, while the mid-Summer group displays several smaller flowers per day on numerous inflorescences in a stratified, three dimensional pattern on tall plants. Both groups demonstrate high fruit set in three breeding systems. Self-pollinating and self-compatible <italic>Calylophus serrulatus</italic> (Nutt.) Raven attracts a diverse forager assemblage, but only small bees less than 10mm. carry adequate pollen loads. Outcrossing vernal species include <italic>Oenothera macrocarpa </italic> Nutt., and <italic>O. speciosa</italic> Nutt. Both species open at night and attract night-flying moths, but <italic>O. macrocarpa</italic> is the preferred nectar reward source for Sphingidae, of which six species foraged in a three tiered, niche-partitioning group. Samples of pre and post-forager levels of nectar reserves indicate that in 1995 and 1996, shorter tongued sphingids were the major or foragers. <italic>O. biennis</italic> L., was weedy and cleistogamous, <italic>Gaura longiflora</italic> Spach, was weedy but outcrossing, and attracted small to medium sized bees in the morning. <italic> G. parviflora</italic> Dougl., was a self-pollinating and self-compatible weed, and <italic>Stenosiphon linifolius</italic> (Nutt.) Heynh. was an outcrosser pollinated mostly by small bees less than 6mm long