Euphydryas

Abstract: Egg clustering is found in certain butterfly groups such as nymphalids, pierids, and acraeids, but rarely in papilionids, satyrids, danaiids, riodinids, and hesperiids. I suggest that the occurrence of butterfly species which deposit eggs in clusters is more common than the literature indicates and that data on egg deposition patterns in natural populations of nymphalids in North America, in particular for Phyciodes, Chlosyne, Euphydryas, and Nymphalis species, would support this conclusion. Egg deposition patterns are a response to the structural and ecological characteristics of the larval host plants. The advantages of egg-clustering appear to be related to aposematic coloration in butterflies (eggs, larvae, and adults), although a particular stage in the life cycle of a butterfly that lays eggs singly may be aposematically colored.

Abstract: RAPID evolution of host association is now occurring independently in two populations of the host-specialist butterfly Euphydryas editha, each of which has recently incorporated a novel host species into its diet. The reasons for these episodes of rapid evolution lie in human land use practices: logging in one case and cattle ranching in the other. In contrast to other insects that have used tolerance of human activities to expand their ranges into disturbed habitats1–3, these rare butterflies have remained at their original sites and evolved adaptations to the changes occurring at those sites. At both sites, the proportion of insects preferring the novel host has increased, in one case clearly because of genetic changes in the insect population. This process is now starting to generate insects that refuse to accept their ancestral host, foreshadowing a new problem in conservation biology. By adapting genetically to human-induced changes in their habitat, the insects risk becoming dependent on continuation of the same practices. This is a serious risk, because human cultural evolution can be even faster than the rapid genetic adaptation that the insects can evidently achieve.

Abstract: A ten-year study of the biology of the Jasper Ridge colony of the nymphaline butterfly Eupkydryas editka has combined yearly estimation of population size and structure with phenetic studies (Ehrlich, 1965; Mason, Ehrlich, and Emmel, 1967; Ehrlich and Mason, 1966). The results obtained have been clarified by behavioral (Labine, 1967), ecological (Singer, unpub.) and genetic (McReynolds, ms.: Singer and Gilbert, ms.) studies through the whole life cycle of the insect at Jasper Ridge. This work has now been expanded into a broad ecological comparison of numerous populations living in different types of community, stressing the relationships between E. editka and other organisms such as food plants, nectar sources and predators. As part of this comparison, interpopulation differences in oviposition preference have been investigated in two ways; by laboratory testing and by direct observation in the field. Where evidence as to proximate mechanisms responsible for these differences can be obtained, this can be regarded as evidence of the mechanisms involved in microevolutionary changes of oviposition preference in E. editha. Such changes in oligophagous insects are usually assumed to be changes in chemotactic response; the literature on insect food-plant preferences, reviewed by Thorsteinson (1960), stresses such chemotactic responses. This paper presents evidence that microevolutionary changes in oviposition preference may occur by means others than changes in chemotaxis. It should be noted that larval food-plant preference is not related to adult oviposition preference in any predictable way, and will be the subject of a subsequent paper in this series. The

Abstract: This paper describes a novel method of measuring host specificity and determining host rank order. As applied to oviposition behavior of the butterfly Euphydryas editha, the rank order of preference is the order in which plants become acceptable as the insect searches, while specificity is quantified in terms of the rate at which searching insects become less discriminating. The information obtained is different from that gleaned from other preference testing techniques. It is useful in helping to assess the behavioral bases of interpopulation differences in the degree of host specialization, in understanding the ways in which multiple host use is generated within a population, and in testing hypotheses about the evolution of host specialization.