A Study of the Relationships of Diapause Phenomena and Other Life History Characters in Temperate Butterflies

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Abstract
A correlation coefficient matrix and 2 way contingency tables reveal multiple associations among the life history characteristics of diapause, voltinism, phagism and distribution. Diapause is at the hub of numerous intercorrelations, a position shared by voltinism. Diapause and voltinism are significantly correlated with phagism and frost-free day (FFD) numbers and range, each of which, in turn, is correlated with 1 or more of the other characters. When these data are treated to a PC analysis, the latent principal components of the intercorrelations become apparent. The major influence on the variations in the patterns of the characters in this study is a result of thermal habitat differences (measured by number of FFD). The niche width or resource diversity of the species (measured by breadth of the thermal range of distribution and diversity of acceptable host plants) and foodplant growth forms (the factor least implicated by simple univariate methods) are also principal components of the patterns of variation of these characters. Discernible patterns emerge with respect to thermal habitats and foodplant growth form and the stage at which diapause occurs. Species which fail to undergo any form of diapause during their life cycle are confined to warm habitats and are most frequently associated with herbaceous host plants. Associations with warmer habitats and woody host plants are apparent for species which undergo reproductive diapause as adults. The species which undergo diapause as pupae are relatively diverse with respect to these factors, but show definite clustering associated with woody host-plant species and relatively warm habitats. Species that undergo diapause as larvae are relatively diverse in relation to the 3 principal components, although a large number of these species are associated with colder habitats and herbaceous host-plant species. In contrast to species which undergo diapause as larvae or pupae, those species which undergo egg diapause are narrowly defined in both thermal habitat and foodplant-type and are associated with cooler habitats and woody host-plant species.