Ecological factors determining population size of Aphis varians.

Research is intended to assess the ecological factor(s) of greatest importance in determining the population size of an aphid (Aphis varians) feeding on fireweed (Epilobium angustifolium). We manipulated the host plant (by shading, watering, and fertilizing), the size of fireweed patches, the density of a leaf-feeding beetle (Altica tombacina) which also utilizes fireweed, and the presence of predators of the aphid (primarily ladybird beetles and syrphid flies) by means of cages.


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