Oral secretions of seven different species of caterpillars, feeding on natural and artificial diets have been analysed by liquid chromatography mass spectroscopy. The compounds present in the caterpillar regurgitates were identified as a structurally diverse group of conjugates of glutamine and glutamic acid linked via an amide bond to saturated and unsaturated C14-, C16- and C18 fatty acids. Proportions of different compounds in regurgitants were species specific.