1974 ] 
S/ansky — Temperate Butterflies 
249 
viewed as a means of utilizing tender, nutritious plant tissue in the 
spring, is seen as an adaptive strategy (c.f. Morse, 1971; Schoener, 
1971). Of course, it is not suggested that the nutritional quality of 
the larval food-plant is of sole importance in determining voltinism 
patterns. For example, larvae of both the Tawny crescent, Phyciodes 
batesii, and the Pearl crescent, P. tharos, feed on Aster; the former 
exhibits one brood and the latter two or three (Table 1). Larvae 
of two Bolaria species and of four Speyeria species all feed on 
Viola; the former exhibit two to three broods, the latter one brood 
(Table 1). There may be differences in the nutritional quality of 
different species of plants within these genera, but other factors 
appear to be causing these differences in voltinism patterns. The 
Least skipper, Ancyloxipa numitor, larvae of which feed on what 
might be characterized as ‘nutritionally poor’ grass plants, exhibits 
two or three broods while the Eastern black swallowtail, Papilio 
polyxenes, larvae of which feed on what might be characterized as 
‘nutritionally adequate’ plants in the Umbelliferae, exhibits but two 
broods (Table 1 ). 
Obviously, the interaction of several other factors (e.g. larval size, 
larval mortality rates, and the presence of adult nectar sources) 
with the nutritive and secondary chemical contents of the larval 
food-plants influences the voltinism patterns. For example, the slow 
growth rates of larvae of P. glaucus may only be ‘permitted’ because 
the combination of the patchy distribution and warning coloration 
of the larvae may reduce mortality losses from predators and para- 
sitoids (J. M. Scriber, personal comm.). On the other hand, the 
rapid growth rates of larvae of P. rapae may be a ‘necessity’ because 
of the nature of its food-plants (i.e., mostly early successional 
species) and because of the high mortality losses of the larvae to 
predators, parasitoids, and disease (Richards, 1940; Pimentel, 1961; 
Dempster, 1969; Parker, 1970). The more rapid growth rates of 
lepidopterous larvae from ‘geographical races’ occurring in regions 
with short growing seasons in comparison to those of larvae from 
regions with longer growing seasons (Goldschmidt, 1940) provides 
another example of the ecological importance of differences in larval 
growth rates. 
Such considerations of the interrelationship of life history phe- 
nomena and population dynamics (e.g. Cole, 1954; Murdock, 1966; 
Istock, 1967; Gadgil & Bossert, 1970; Morse, 1971 ; Schoener, 1971 ; 
Willson, 1971) raise a number of ecologically relevant and as yet 
insufficiently answered questions, such as : 
