Laboratory and Field Observations of the Behavior of Eustenopus villosus while Feeding and Ovipositing on Yellow Starthistle

Abstract

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.

Evaluation of the Impact of Eustenopus villosus on Centaurea solstitialis Seed Production in California

“…The difference between puncture rates and larval infestation rates may be due to the lack of deposition of eggs. Punctures in mature capitula result from either simple feeding or oviposition [ 31 , 33 ] and, in a separate study, we found that 63% (range 60–67%) of punctures resulted in egg deposition (unpublished data). Another possibility is that eggs and young larvae experience high rates of mortality.…”

“…Adult weevils emerge in late spring and undergo a period of host feeding. Adults of both sexes feed on young flower buds (<3 mm in diameter) [ 30 , 31 , 32 ]. This early bud feeding can be severe and many plants can lose all initial flower buds.…”