Population structure of pierid butterflies : III. Pest populations of Colias philodice eriphyle.

Mark-release-recapture techniques were used to study alfalfa pest populations of Colias philodice eriphyle. Two new methods for estimating relative catchability and residence rates were used to compare males to females. The results show that: (1) both sexes had limited dispersal, with mean individual ranges less than 100 m; (2) males were more abundant than females; (3) males and females had similar residence times; (4) males were more catchable than females in uncut fields, but not in cut fields. Explanations for the differences between the sexes are considered. Females may be less catchable in uncut fields because they spend less time in flight than males. Males may be more abundant than females because they develop faster, and may have lower pre-adult mortality. The differences between the sexes are discussed with respect to reproductive strategy. Comparisons with non-pest C.p. eriphyle show differences between pest and non-pest populations. Pest C.p. eriphyle were more sedentary. The residence times were similar for pest and non-pest populations, but pest C.p. eriphyle probably have longer "reproductive life-spans". Mid-summer broods of the pest population were partially overlapping; the non-pest population has discrete broods. Pest population density varied less between years than non-pest population density. The differences between pest and non-pest C.p. eriphyle support the idea of ecological diversity among conspecific populations.