Strong decrease in egg mass on subsequent days of oviposition generates little variation in offspring performance in the pine‐tree lappet moth, Dendrolimus pini

The pine‐tree lappet moth, Dendrolimus pini (L.) (Lepidoptera: Lasiocampidae), is a pest whose natural range mostly follows that of its host, Scots pine, Pinus sylvestris L. (Pinaceae). Under natural conditions, we observed differences in larval body size, pointing to different rates of their growth and development. This study aimed to check whether differences in egg mass can differentiate the growth and development rate of D. pini larvae. We assumed that decrease in egg mass on subsequent days of oviposition can have a large impact. Our results indicate that there is an unusually strong fecundity advantage of large female mass in D. pini, but with each day of laying, the mean mass of the eggs decreases. However, offspring phenotype and development in D. pini is not clearly correlated with egg mass. We also confirmed a strong decrease in the number and mass of eggs on subsequent days of oviposition. However, egg mass decline did not correspond with the performance of the offspring in a laboratory rearing because the specimens formed from ‘medium‐mass’ eggs were characterized by the highest fitness. Although we noted a significant impact of the day of oviposition on some offspring's fitness parameters (e.g., development stage duration, pupal mass, adult mass), the variation was not large. The offspring hatched from eggs on the 3rd day of oviposition were characterized by increased values of some parameters (e.g., higher mass, heavier cocoons, faster development). Variation in the development of the larvae could be a strategy to help offspring survive under short‐term unfavorable conditions, and also reduces intra‐species competition which is generally beneficial.