none The parasitoid-system Pieris brassicae-Apanteles glomeratus was used to investigate the influence of low concentrations of pesticides on the endoparasite in relation to the structure during chronic feeding in the chain: food-host-endoparasite. Collectives of each 15 non-parasitized (np) and parasitized (p) Pieris -larvae per pesticide (lindane, parathion, monolinuron, hexachlorobenzol (HCB)) were fed with super(14)C-labelled pesticides on cabbage during their 6 day L5-stage. Larval and post-larval radioactivity transfer rates were determined. The beneficial organism, the braconide wasp was able to get rid of as much as 80% of the residues through cocoon-, plus silk-, plus metabolic product formation of all the four pesticides tested.