Impact of superparasitism time intervals on progeny survival and fitness of an egg parasitoid

Abstract

1.Superparasitism influences the fitness of female parasitoids and their progeny, and increasing time interval between oviposition bouts generally reduces survival probabilities of the second clutch. However, the timing of superparasitism may, under certain conditions, favour the second clutch.2. This study investigated the effects of superparasitism time intervals on survival and fitness of both clutches, allowing the egg parasitoid Trichogramma euproctidis to parasitise previously parasitised Ephestia kuehniella host eggs at different time intervals.3. In short intervals (0–1 h), a significant advantage was found for the second clutch over the first clutch (93.1% survival). In contrast, the second clutch was outcompeted by the first clutch in 17–19 h and 27–29 h intervals. Females deposited their eggs into larvae (intraspecific hyperparasitism) in a 39–41 h interval with a probability of survival of 57.1%. Females mostly refused to hyperparasitise pupae (∼80% rejection at 124–126 h), and when they did, their progeny never survived.4. Hyperparasitism significantly increased parasitoid mortality in both clutches from less than 20% (superparasitism only) to over 35%.5. Except on newly laid eggs (0–1 h), superparasiting females were frequently observed attempting to stab immatures of all stages (from 36.4% to 89.4% of all ovipositions depending on treatment), but infanticide only appeared to succeed on larvae (39–41 h).6. When the second clutch survived, emerging parasitoids were smaller than control individuals, probably due to resource depletion.7. These results suggest that T. euproctidis females can detect that a host has been previously parasitised but they cannot perceive superparasitism time intervals.