MALE PERIODICITY AND THE TIMING OF MATING IN THE SPRUCE BUDWORM (LEPIDOPTERA, TORTRICIDAE) - INFLUENCES OF POPULATION-DENSITY AND TEMPERATURE

Male spruce budworm diel trapping periodicity using artificial polyvin yl chloride (PVC) lures, virgin female baited traps, and blank traps w as examined from 1988 to 1990 at sites having different population den sities. The diel periodicity of female emergence and mating initiation were also determined. Patterns of male trapping periodicity differed substantialy by density and lure type but not by temperature. Virgin f emale baited traps detected unimodal male periodicity at all densities . PVC traps detected unimodal trapping pattern in the low density site s and bimodal patterns (1 morning and 1 evening peak) in high-density sites. No significant temperature effect on male trapping periodicity was detected. The upper and lower male flight temperature threshold wa s 11.5 and 27.5 degrees C, respectively. Female emergence was dependen t on the thermoperiod and peaked around 1300 hours. The pattern of mat ing initiation (beginning of copulation) differed significantly with d ensity and coincided with peak PVC trapping periodicity. In low-densit y populations the majority of matings were initiated by 2100 hours, du ring the known female calling period; in high-density populations, the majority of matings were initiated by 1300-1900 hours, before the kno wn female calling period. The coincidence of earlier mating and male c atches at PVC-baited traps (but not at virgin female baited traps) sit uated in high-density areas, together with the coincidence of later ma ting and later catches in PVC and virgin female baited traps in low-de nsity areas cannot be explained by differences in the thermoperiod or differences in the timing of female attractiveness. An appetitive, mal e mate-searching strategy not requiring calling females is discussed.