Professor Kyushu University Fukuoka, Fukuoka, Japan
Morphological traits of egg masses could limit accessibility of parasitoids that are attempting to oviposit in them. In a single layer egg mass consisting of three or more rows, for example, only the upper surface of the center eggs that are surrounded by other eggs are exposed to parasitoid’s attack, which may reduce parasitism rate. The parasitoid Paratelenomus saccharalis parasitizes eggs of the kudzu bug Megacopta cribraria, which is native to Asia and invaded southeastern United States. Like other plataspids, M. cribraria females lay egg masses that each consists of 10-50 barrel-shaped eggs laid horizontally with two rows on host’s food plants. To determine whether this egg arrangement of M. cribraria egg mass affects accessibility of P. saccharalis, we examined oviposition success (the proportion of successful ovipositions in oviposition attempts) by P. saccharalis on different ages of M. cribraria eggs. When attacking terminal eggs of 0-day-old egg masses, they drilled the exposed lateral side of the egg and successfully oviposited with 97% of times. When attacking center eggs, however, they drilled the exposed upper side of the eggs or the under side of the eggs, and oviposition success was 60%. For 4-day-old egg masses, oviposition success rate was 45% on terminal eggs and 10 % on center eggs. For 0-day-old and 4-day-old egg masses, Oviposition success by P. saccharalis was significantly lower on center eggs than on terminal eggs. These results demonstrate that M. cribraria egg mass structure reduces accessibility to eggs by P. saccharalis.
