Oviposition behavior and response to the oviposition scars occupied by eggs in Monochamus saltuarius (Coleoptera: Cerambycidae)

The oviposition behavior and response of Monochamus saltuarius females to already-made oviposition scars were investigated in the laboratory. The females gnawed at the bark surface of Pinus densiflora bolts to make a wound, turned the bodies 180 degrees to position the ovipositors over the wounds and inserted the ovipositors under the bark through the wounds. About 7 min later, the females withdrew the ovipositors from the bolts. In most cases, the ovipositor-inserted small holes of the oviposition scars made in this way were plugged with jelly, and the females left the scars after rubbing them with the abdomens. When females searching for an oviposition site encountered oviposition scars occupied by single eggs, they stopped walking and then palpated the surface of the oviposition scars with the maxillary and labial palpi. Eighty-five percent of the females left the scars after the palpation. In contrast, when the females encountered oviposition scars containing no eggs, 73% of them began to gnaw at the scars after the palpation and 48% deposited eggs singly. The response to artificial, mimic oviposition scars was the same as that to Vacant oviposition scars made by the females. The results of observations and experiments showed that the females could discriminate oviposition scars occupied by single eggs from Vacant scars and suggested that the palpation of oviposition scars was closely related to the discrimination, indicating mediation by chemical and/or physical cues.