RESPONSE OF THE PINE WEEVIL HYLOBIUS-ABIETIS L (COL, CURCULIONIDAE) TO HOST VOLATILES IN DIFFERENT PHASES OF ITS ADULT LIFE-CYCLE

The response of adult Hylobius abietis L. before and after the spring flight period and in autumn to host volatiles was studied in field experiments using pitfall traps and trapping billets. In spring and early summer, pitfall traps baited with alpha-pinene + ethanol caught more pine weevils than traps baited with pine stem pieces. In autumn, the reverse was true. In autumn, newly emerged prereproductive females were caught in pine baited traps and at trapping billets, but not in traps baited with alpha-pinene + ethanol. In spring before the flight period, traps baited with alpha-pinene + ethanol caught similar numbers of prereproductive and reproductive females, whereas nearly all females caught in pine baited traps and at trapping billets were prereproductive. The differences in responses to olfactory stimuli between phases of the adult life cycle reflect seasonal differences in behaviour and should be taken into account in trapping methods based on olfactory orientation, particularly methods for population estimates.