Interspecific Iarval competition among three egg parasitoid species on the host, Riptortus clavatus (THUNBERG) (Heteroptera: Alydidae)

Abstract

Interspecific competition among three major egg parasitoids, Ooencyrtus nezarae ISHII, Gryon japonicum (ASHMEAD) and G. nigricorne (DODD) of the bean bug, Riptortus clavatus (THUNBERG) (Heteroptera: Alydidae), was examined using the host eggs attacked at various intervals in laboratory experiments.
The outcome of interspecific competition between 0. nezarae and either of the Gryon species depended on the order and interval of attacks. Gryon species did not oviposit host eggs parasitized 7 or more days previously by 0. nezarae. 0. nezarae emerged from host eggs when it had a head start of at least 3 days on its competitor. This parasitoid seemed to be a facultative secondary parasitoid of the Gryon species when it attacked hosts 3-7 days after an attack by the Gryon species. However, Gryon species tended to be the successful competitor when the parasitoids attacked the hosts at a short interval of 1 day or less. In the combination of two Gryon species, multiparasitism by both species occurred if the oviposition interval was 3 days or less. The competition was asymmetric in this case and G. nigricorne had a consistent advantage over G. japonicum.