DIFFERENTIAL POSTALIGHTMENT OVIPOSITION BEHAVIOR OF MONARCH BUTTERFLIES ON ASCLEPIAS SPECIES

The monarch butterfly, Danaus plexippus L., oviposits mainly on plants in the Asclepiadaceae, particularly within the genus Asclepias. We st udied postalightment oviposition behavior of monarch females on three host species-Asclepias curassavica, A. incarnata, and A. tuberosa. Aft er landing on the host, they used their forelegs, midlegs, and antenna e to assess plant suitability. When these appendages were examined by scanning electron microscopy, contact chemoreceptor sensilla were foun d. In choice tests, A. incarnata was most preferred, while A. tuberosa was least preferred. However, the use of appendages varied for the di fferent host species. Antennae were most frequently used during postal ightment behavior on A. curassavica, whereas forelegs were used more o ften on A. incarnata, and all three appendages were used extensively o n A. tuberosa. Use of the midlegs was generally followed by use of the antennae. Tasting with either forelegs or antennae apparently may lea d to egg laying on some host species. Rupture of the plant surface by midleg spines was also observed. The behavior and host preference of i ndividual females varied significantly and may reflect differences in receptor sensitivity.