acetylcholinesterase and heat shock protein 70 response in larval brain tissue of lymantria dispar l lepidoptera limantriidae upon chronic exposure to benzoapyrene the effects of different concentrations of benzoapyrene bap 2 10 20 100 200 and 2000 ngg dry food weight on the activity of acetylcholinesterase ache and concentration of heatshock protein 70 hsp70 in fifth instar lymantria dispar brain tissue were investigated inhibition of ache is a general effect biomarker at the individual level we observed the most efficient inhibition of this enzyme at medium and high bap concentrations 20 100 200 and 2000 ngg dry food weight western blot analysis revealed the presence of two hsp 70 isoforms with changed amounts depending on the bap concentration a fluctuating response in hsp70 concentration to ingested bap was observed with decreased levels in the groups fed 2 and 100 ng bapg dry food weight but increased concentrations in the groups given 10 and 2000 ngg dry food weight even though we detected changes in ache activity and hsp70 concentration in l dispar brain tissue upon exposure to different bap concentrations we cannot characterize them as sensitive and reliable biomarkers for this xenobiotic in l dispar caterpillars