Development of ovaries, allometry of reproductive traits and fecundity of Epi syrphus balteatus (Diptera: Syrphidae)

Abstract

Episyrphus balteatus only matures eggs after emergence. Ovaries develop in 4 stages. In the absence of oviposition sites, females refrain from ovipositing and their ovaries progressively fill the abdomen and then egg resorption occurs. The potential fecundity, which is expressed by the ovariole number, the reproduc tive biomass and the abdomen volume, scales isometrically with the size of females. Egg size is much less variable and does not rise proportionally to body size. In laboratory conditions, females of E. balteatus might lay between 2,000 and 4,500 eggs during their life-time at a rate of 1 to 2 eggs per ovariole per day. Both lifetime fecundity and rate of egg production are directly related to the size of females. The potential and realized fecundities are likely to be limited by the availability of fo od resources during larval and adult life, respectively.