Laboratory and Field Observations of the Behavior of <Emphasis Type="Italic">Eustenopus villosus</Emphasis> while Feeding and Ovipositing on Yellow Starthistle

The feeding and oviposition behavior of postdiapausal Eustenopus villosus (Boheman) on young and late stage buds, respectively of yellow starthistle, Centaurea solstitialis L., was documented in the laboratory and field. Postdiapausal adult feeding on young buds took over an hour to complete in most cases and was conducted by both sexes. Feeding bouts generally occurred in the sequence of explore, feeding, and budwalk. Oviposition included a feeding phase to prepare an oviposition cavity within the bud; thus, oviposition bouts included some of the same behavioral elements as postdiapausal feeding. The standard sequence of behavioral elements involved with oviposition included exploring, feeding, turning, ovipositing, and budwalking. The feeding element during the oviposition bout often lasted 2 h and was similar in the field and in the lab. Postdiapausal adult feeding on young capitula and stems, and larval feeding on developing ovaries and achenes, makes this weevil especially destructive on a per insect basis.