Ovipositional Behavior and Site Selection by a Sunflower Stem Weevil, Cylindrocopturus Adspersus (Coleoptera: Curculionidae)1

Abstract

Initial oviposition sites of Cylindrocopturus adspersus (Le Conte) were in the glabrous zones around the cotyledonous (first node) and second nodes, but they moved up the main stalk below successive leaf axils as the growing season progressed. Female C. adspersus oviposited at a mean height of 4.5 cm above the first node area in 1980 and 20.7 cm above the first node in 1981, which encompassed utilization of the lower 6 and 17% of the stems in 1980 and 1981, respectively. Oviposition a greater distance above the cotyledonous node in 1981 than in 1980 probably was due to increased weevil populations, and to increased competition for egg deposition sites. Fifty percent of oviposition occurred on a date separated by only 5 days in successive years.