Oviposition and developmental performances of the gregarious hyperparasitoid Cheiloneurus nankingensis in relation to host age

Abstract

Native generalist hyperparasitoids may not take long to exploit non-native parasitoids as hosts. The gregarious obligate hyperparasitoid Cheiloneurus nankingensis (Hymenoptera: Encyrtidae) was recently found in China as a new species to science and it attacks the non-native parasitoid Aenasius arizonensis, which is a potential biocontrol agent accompanying its host the cotton mealybug Phenacoccus solenopsis during the invasion into Asia from North America. To determine the developmental strategy of this hyperparasitoid in relation to host age, we exposed A. arizonensis at varying ages developing in solenopsis mealybugs to hyperparasitism by C. nankingensis females. We found that female hyperparasitoids tapped their antennae with decreasing frequency and duration on middle-aged hosts compared to the younger and older ones. Female hyperparasitoids decreased the frequency of ovipositor insertion into middle-aged hosts compared to the younger and older ones, while the total duration of ovipositor insertion overall increased with host age. The probability of hyperparasitism success to production of offspring adults showed a dome-shaped curve with host age with a plateau between host ages of about 5 and 10 days. Realized brood was large around the age of 5 days and declined with younger and older hosts. Egg-to-adulthood time did not vary with host age. Sex ratio stayed alike around 0.3 (male proportion in a brood) across host ages. Body size and longevity of offspring adults did not vary with host age. Our results suggest that while a wide range of ages of A. arizonensis larvae are susceptible to hyperparasitism by C. nankingensis the middle-aged larvae are of higher quality.