OLFACTORY ORIENTED MIGRATION THROUGH SOIL BY ROOT-LIVING HYLOBIUS-ABIETIS (L) LARVAE (COL, CURCULIONIDAE)

The pine weevil Hylobius abietis (L.) is known to oviposit in the inner bark of roots of recently killed coniferous trees, where larvae develop as subcortical feeders. In laboratory experiments we demonstrated that many H. abietis larvae abandoned a crowded host substrate and migrated through sand to a previously unoccupied substrate 100 mm away, where they established themselves. Ethanol and the host monoterpene alpha-pinene were shown to act synergistically in attracting the larvae. Larval migration towards fresh host material was demonstrated also in first instar larvae hatching from eggs laid in sand more than 50 mm away from the host substrate. Oviposition in the sand was induced by denying the ovipositing females access to the host material by covering it with nylon mesh. We suggest that the facultative migratory behaviour shown by H. abietis larvae in the two situations reported here can play an important role in increasing their survival as well as their ability to utilize available host material in the field.