AGRAULIS AND PASSIFLORA I. CONTROL OF SPECIFICITY

¹ Department of Biological Sciences, University of California, Santa Barbara, California 93106

1. Prior to an investigation of the sensory modalities and behavior involved in host-plant selection by Agraulis vanillae incarnata (Riley), experiments were conducted to evaluate the relative influence of larval feeding behavior, adult ovipositional behavior, and host-specific butterfly mortality in determining the infestation of various species of host-plant in the genus Passiflora.

2. The larvae demonstrated induced feeding preferences for some, but not all, species of Passiflora upon which they had previously been raised.

3. The adult females exhibited definite, fixed ovipositional preferences among six species of Passiflora available in Santa Barbara County. These preferences were not affected by either larval diet or induced feeding preference.

4. The food plant suitability of the six local species of Passiflora varied considerably as indicated by several aspects of Agraulis growth, development, and reproduction. With a few notable exceptions this food plant suitability broadly correlated with the adult ovipositional preferences as predicted by Wiklund's model for the evolution of ovipositional preferences. The exceptions are discussed in terms of what they may reveal about the development of the Agraulis-Passiflora association in southern California.

5. The results of a field survey of host-plant infestation by Agraulis did not entirely fit predictions based on the above experimental results. The levels of infestation of the various species of Passiflora appear to correlate more closely with the ovipositional preferences of the adult females than with any of the other parameters studied.

6. The ovipositing females primarily determine the degree to which each species of Passiflora in Santa Barbara County becomes infested. The influence of larval behavior is negligible. The distribution of Agraulis among its host-plants is the result of an active process and is not, except in an evolutionary sense, determined by passive factors such as mortality on unsuitable food plants.