Egg weight variation in the butterfly Lycaena hippothoe : more small or fewer large eggs?

Fecundity, egg weight, hatching success of eggs, and adult (offspring) weight were compared between three geographically separated populations (i.e., subspecies) of the butterfly Lycaena hippothoe . All these traits differed substantially between populations. Our data suggest that, on an interpopulational level, egg size is traded off against egg number, egg size varies independent of adult size, and there is (given equal egg size) a positive relationship between adult weight (body size) and fecundity. The significantly heavier eggs of the alpine population Lycaena hippothoe eurydame showed strikingly increased hatchability, especially at high temperatures, as compared to the other populations. However, the ultimate reasons favoring large egg size in the alpine population, whether as a result of direct selection on egg size, as a correlated response based on other selective pressures, or reflecting relaxed selection for maximized fecundity, remain to be discovered.