Oviposition Habit of the Japanese Pine Sawyer, Monochamus alternatus HOPE (Coleoptera, Cerambycidae) : II. Effect of Bark Thickness on Making Oviposition Scars

Experiments were carried out in the laboratory room at Kagawa University in 1991 to clarify the effect of the bark thickness on making oviposition scars of the Japanese pine sawyer, Monochamus alternatus HOPE. Females were released on the Japanese black pine, Pinus thunbergii PARL logs with different bark thickness and oviposition behavior was observed continuously. The mean number of oviposition scars on thin barked logs (2.0-2.5mm) was larger than thick ones (5.3-6.5mm), but the difference was not statistically significant. The mean number of oviposition scars in which females inserted ovipositor (scars with insertion) on thin barked logs was significantly larger than thick ones, when females were released on two logs with thin and thick bark. The mean number of scars per log became smaller with the increase of bark thickness. The rate of scars with insertion to oviposition scars in thick barked logs (more than 5mm) were significantly smaller than thin logs. The time of making oviposition scars became longer with the increase of bark thickness. Female's preference for oviposition sites in a pine tree was discussed from the results.