THE INSECT ECOLOGY OF RED PINE PLANTATIONS IN CENTRAL ONTARIO: V. THE COCCINELLIDAE (COLEOPTERA)

Abstract

Thirteen species of Coccinellidae were found to occur in adjacent red pine plantations of five different ages near Thessalon, Ont. These populations fell into two major ecological groups corresponding to the two plantation age classes. One group (the old-field species) inhabited young plantations up to 16 years old, and the other (the old-stand species) inhabited older stands. Each group was characterized by different dominant species, Coccinella transversoguttata Falder-man and Scymnus lacustris Lec. in the younger stands, and Mulsantina picta (Rand.) and Anatis mali Auct. in the older stands. Species diversity decreased as the stands aged.As the red pines increased in size, they became less favourable for coccinellids in general because prey density decreased. As a consequence, the predator’s search area per unit prey capture increased necessitating an increased searching capacity and mobility. Coccinellid population fluctuations were synchronized with those of the woolly pine needle aphid, Schizolachnus piniradiatae (Davidson), the major food source, due to compensative movements to and from the plantations of the adult coccinellids and the dependence of the larvae on the aphid. Starvation and cannibalism during the larval stages appeared to be the major mortality factors. Inclement weather and predation were of minor direct importance to coccinellid populations and parasitism was rare.All species, with the possible exception of S. lacustris, were univoltine.