Family structured patterns of mortality in the false Colorado potato beetle

Abstract. 1. The distribution of mortality within and among groups of immature Leptinotursu juncta (Germar) (Coleoptera: Chrysomelidae) was studied in the field at three points in the life‐cycle in order to test whether the fates of individuals occupying the same host plant were non‐independent. 2. Studies were conducted on eggs subject to cannibalism and predation, on newly hatched larvae subject to predation, and on older larvae subject to parasitism by Myiophurus doryphorue (Riley), a tachinid fly. 3. At all three points in the life‐cycle the variance in group‐specific survivorship rates was demonstrated to be significantly greater than expected when individual deaths are distributed randomly among groups, with standardized variances ranging from 42% to 52% of the maximum possible. 4. A statistically significant positive correlation was shown between the number of individuals in a group and the group‐specific survivorship rate at all three life stages. 5. The distribution of genetic variants within and among groups of larvae showed the groups to be mixtures of full and half siblings, with an average coefficient of genetic relatedness, r , equal to 0.38.