Oviposition behavior of Anagrus nigriventris,an egg parasitoid of beet leafhopper, Circulifer tenellus

Abstract

Oviposition behavior of Anagrus nigriventris,a parasitoid of the eggs of the beetleafhopper,Circulifer tenellus, wasdescribed on sugar beet. Ovipositor probes ofrelatively long duration were accompanied by a periodof abdominal vibrations toward the end of the probe. These periods began as high frequency, low amplitudevibrations in the abdomen, and climaxed as a tremblingof the whole body in an up and down direction.Oviposition by the parasitoid was associated with theoccurrence of abdominal vibrations during a probe andwith probe durations ≥50 s; however thepresence/absence of abdominal vibrations during aprobe was considered a more reliable indicator ofoviposition than was a threshold probe duration of 50s. The majority of probes (63% of all probes) were inempty plant tissue, lasted 15 s, and were notassociated with abdominal vibrations. While probeswithout abdominal vibrations at host egg sites (14%of all probes) lasted an average of 48 s, probes withabdominal vibrations at host egg sites (23% of allprobes) lasted an average of 102 s, and all were ≥50s. It is hypothesized that the relative frequency ofthe 3 types of probes could be affected by the degreeof wasp experience, by the level of host cues on thesubstrate, and by the relative importance of ovipositor probing (vs. antennation) in the hostdetection process. Data from the study suggest thatA. nigriventris is able to discriminate againstpreviously attacked host eggs.