Repeated probing of hosts: An important component of superparasitism

Abstract

Parasitoids that encounter a previously parasitized host inspect it externally and internally, sometimes eventually laying additional eggs (superparasitism). The fitness effects of increased clutch sizes generated through superparasitism are widely studied, whereas the consequences of multiple host probings during the inspection received less attention. To address this issue, we offered a host to 1-5 females of the encyrtid wasp Copidosoma koehleri consecutively, or presented it 1-5 times to a single female. We noted whether the hosts died before pupation of either host or wasp, produced parasitoid pupae, or developed into moth pupae. Additional hosts were dissected after varying numbers of probings to determine their parasitoid egg loads. Host rejection rates prior to ovipositor insertion did not differ between treatments. Host rejections after ovipositor insertion, characterized by brief (<10 s) probing durations, were more common in the single-than in the multiple-female treatment. This could reflect avoidance of self-superparasitism, or increased selectivity by host-experienced females. Egg number per host increased with the number of prolonged probings in both treatments. Some hosts that received 1-2 probings (brief or prolonged) yielded moth pupae, while no hosts with five probings survived to pupation. Hosts probed three times (corresponding to <1 and 2.2 eggs in the single-and multiple-female treatments, respectively) produced the largest proportion of parasitoid pupae. The parasitoids' success is thus strongly affected by the number of host probings. Overcoming host defenses through repeated probings is a previously overlooked potential benefit of superparasitism. © 2012 The Author.