Influence of Cohabitation and Resinosis on Site Selection and Survival of Pineus boerneri Annand and P. coloradensis (Gillette) (Homoptera: Adelgidae) on Red Pine

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Abstract
Density and survivorship of solitary and coexisting populations of Pineus boerneri Annand and Pineus coloradensis (Gillette) (Homoptera: Adelgidae) were studied for 3 years in 12 stands of red pine, Pinus resinosa Aiton, in Connecticut and Rhode Island. Survival of P. boerneri was higher on branches than on needles during winter but higher on needles than on branches during spring and summer. Survival of P. coloradensis was always higher on needles than on bark. The percentage of branches that were resinous (indicative of injury) increased at four coinfested pine stands from 1980 to 1982. The proportion of the P. boerneri population on needles relative to bark increased during that period; the opposite trend was observed for P. coloradensis. Decreasing density of P. coloradensis on needles was related to increasing density of P. boerneri, and was due to a combination of greater mortality on needles and greater colonization of bark, where chance for survival was even less. P. boerneri established and maintained numerical dominance over P. coloradensis in these four coinhabited pine stands and on pine seedlings in the greenhouse.