<jats:p>The chemical defensive system of the ladybird Cryptolaemus montrouzieri consists mainly of three related alkaloids. Two of these have been identified as cis-1-(6-methyl-2-piperidyl)propan-2-one (3) and 1-methyl-9-azabicyclo[3,3,1]nonan-3-one (2); the third is very unstable and readily isomerizes to (3).