Seasonal patterns of insect damage to reproductive tissue of the legume Baptisia australis were studies for three years in native tallgrass prairie. Contrasting seasonal patters of damage were associated with the major species of insect consumers. The moth Grapholitha tristegana (Olethreutidae) and the weevil Tychius sordidus (Curculionidae), which together infested 80-100% of developing fruits (pods), consistently damaged more seeds on average in early than in late maturing pods. But while late opening flowers were less subject to attack from moths and weevils, they were more subject to attack from chewing insects, particularly blister beetles (Epicauta fabricii, Meloidae), which destroyed more than 80% of all flowers and developing young pods (including moth and weevil larval inhabitants). The blister beetle arrived late in the flowering season and fed particularly on young reproductive tissue, allowing larger, older pods that had developed from early opening flowers to escape destruction. The relative abundances and impacts of blister beetles, moths, and weevils varied from year to year. Adding to the uncertainty of reproductive success of the host plant were the large and variable amounts of damage to immature buds inflicted by insects (including the blister beetles and weevil adults) and late killing frosts. Thus, timing of flowering is critical to success in seed production for B. australis. The heavy impacts of insects and weather can result in a very narrow window in time (which shifts from year to year) during which B. australis can flower with any success. The opposing pressures exerted by insects and weather on floral reproductive success may act in concert with other features in the plant's biology to foster the maintenance of considerable diversity in flowering times among individuals in local populations of B. australis. Key words: flowering time, grassland, herbivory, phenology, seed predation