The Interrelationship of the Aphid, Acyrthosiphon Pisum, and Its Parasite, Aphidius Smithi, in a Stable Environment

Abstract

The interrelationship between the aphid, Acyrthosiphon pisum (Harris) and its parasite, Aphidius smithi Sharma & Shubba Rao, was studied in two strip harvested alfalfa fields near Famoso, California in the summer of 1963. Strip harvesting had a stabilizing effect on the alfalfa environment particularly as regards micro climate. As a result both Acyrthosiphon and Aphidius remained highly active in midsummer. By contrast in previously studied solid harvested alfalfa fields both species were strongly depressed during summertime. The current studies also produced information on migration of female Aphidius and on the wasp's density dependence.