Apion rostrum Say (Coleoptera: Apionidae) is the major seed predator of the wild indigo congeners, Baptisia alba and B. bracteata in the Russell Kirt Tallgrass Prairie, a reconstructed prairie located at College of DuPage, Illinois. This study, conducted during 2006, investigated factors attracting A. rostrum to each congener. The two Baptisia differ in developmental period, stature, and patterns of dispersion. B. bracteata flowers and initiates pods usually along a single raceme during late spring, and is a shorter plant that grows in clusters. In contrast, B. alba flowers and initiates pods beginning a month after B. bracteata, produces a tall central raceme with often several satellite racemes, and does not grow in dense clusters. Mating and ovipositing A. rostrum were observed on B. bracteata during the first half of June, and with greater abundance on B. alba from early June through mid July. Results of stepwise multiple regression showed a positive relationship of weevil counts per plant to raceme counts per cluster for B. bracteata and to inflated pod counts per plant for B. alba. The developmental synchrony between A. rostrum and pods of B. alba is evidence of a closer evolutionary relationship than the seed predator has with B. bracteata. This can explain the greater number of reproductive weevils seen on B. alba as well as the higher levels of pod infestations
