FACTORS INFLUENCING THE RESPONSE OFIPS CONFUSUS(COLEOPTERA: SCOLYTIDAE) TO MALE ATTRACTANT

Abstract

Various aspects of the behavior of I. confusus (LeConte) relating to the production of and response to male attractant were studied. Storage at 8.0 °C and 100% R.H. had no adverse effect on survival, response to male attractant, or predisposition to fly. Low humidity and high temperatures (21 °C) adversely affected behavior and survival. Beetles conditioned either in natural or constant environments responded at high levels throughout a 24-hour period. Female response to male frass reached a low of 24.2% in January and February and rose to a peak of 76.6% in May and June. Response to benzene extract of male frass fell moderately during autumn and winter, indicating a lowered response ability for overwintering populations. Male response was lower and more erratic but followed the same seasonal trends.After brief exposure periods, even previous nonresponders oriented to male attractant at significantly higher levels than the total original population. Long-term confinement in an atmosphere containing male frass odor caused a reduction in response of both sexes to male frass extract, presumably because of adaptation of olfactory receptors.Flight attempts by both sexes occurred between 25° and 40 °C but were severely inhibited at these extremes. Light intensities below 431 luxes suppressed flight. Optimal take-off temperatures were 30 °C for males and 32.5 °C for females. Both contact with male frass and with attractive air reduced the take-off attempts of both sexes to near zero. Attractive odor in the air still suppressed flight significantly after beetles had been conditioned up to 4 hours in contact with male frass.Teneral males produced attractant after a long maturation period. Single, mature males produced attractant up to 18 days, but after mating, productivity declined in direct correlation with the number of females per male. Single males produced frass throughout the day but maximum production was coincident with peak female emergence and flight. Male frass was significantly less attractive 15 minutes after exposure to open air and after 1 hour, very little attraction remained.No trends in the ability of newly emerged adults to respond to male attractant were noted over a 30-day period. Emerging brood and re-emerging parent adults are responsive to flight stimuli, but darkened callows and parent adults removed from galleries could not be induced to fly. Reproducing females show a greatly reduced response to male attractant.