Acidic methanolic, whole body extracts of larval Tenebrio molitor (Insecta, Coleoptera) and other juvenile insects are highly toxic to adults of the same species and other species: injection causes instant paralysis to death. Referring to their dramatic effect in mature insects, the responsible compounds have been designated as "paralysins." Two paralysins have already been identified in the flesh fly, Neobellieria bullata, i.e., beta-alanine-tyrosine (BAY) and 3-hydroxykynurenine (3HK). We report here the isolation, from larval T molitor, of two additional paralysins, respectively, the essential amino acid, tryptophan (Trp), and the saturated beta-carboline, 1,2,3,4,-tetrahydro-beta-carboline-3-carboxylic acid (THCA). (C) 2003 Elsevier Inc. All rights reserved.