Two species of ants, Formica obscuripes Forel and Dolichoderus (Hypoclinea) taschenbergi (Mayr), attended species of Cinara, mainly C. gracilis (Wilson) on Pinus banksiana Lamb., in the Sandilands Forest Reserve, Man. The aphids occurred only on trees near ant hills. Removing the aphids by spraying had no serious effect on the ants. Destruction of an ant colony was followed by the disappearance of the aphids. The trees benefited through removal of defoliating insects by the ants.
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Bradley et al. (1968) studied this question.
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