BIONOMICS OF THE 4-EYED SPRUCE BARK BEETLE, POLYGRAPHUS-RUFIPENNIS (KIRBY) (COL, SCOLYTIDAE) IN NEWFOUNDLAND .2. HOST COLONIZATION SEQUENCE

The four-eyed spruce bark beetle, P. rufipennis, is a phloeophagous ba rk beetle restricted to Abietineae hosts in northern and mountainous a rea of North America. Projected wood shortages in Newfoundland have fo cused attention on the bark beetle and its role in contributing to bla ck spruce mortality. Our findings disclosed that colonization on felle d and standing trees by P. rufipennis followed the typical host select ion sequence of scolytids, notably, emergence, dispersal, selection an d establishment. All brood stages except eggs overwintered in black sp ruce, however, the majority of overwintering stadia consisted of larva e and callow adults. Adult mortality was significant during winter, es pecially in standing severed and felled trees. In Newfoundland, P. ruf ipennis had 1 generation and produced a spring and summer brood. Four weeks after establishing a first brood, parent adults re-emerged to es tablish a second brood. Development from egg to adult took approximate to 2 months. P. rufipennis of either sex initiated attack at mean den sities per 100 cm(2) of 8.1 and 9.3 on felled and standing-severed tre es, respectively. Densities were significantly lower at 4.7 per 100 cm (2) on standing unsevered trees. Following copulation, males stayed wi th the females and exhibit guarding behaviour by occupying the entranc e hole. Significantly higher numbers of galleries were established on trees felled in shade than in full sunlight. Black spruce attacked by P. ruipennis were often secondarily attacked by Dryocoetes affaber and Crypturgus borealis. Other associates included Medetera sp. and the c ylindrical bark beetle, L. intricatus.