METABOLISM AND ELIMINATION OF INGESTED ALLELOCHEMICALS IN A HOLOMETABOLOUS AND A HEMIMETABOLOUS INSECT

Experiments were conducted to test the hypothesis that hemimetabolous insects such as Orthoptera utilize physical barriers in the gut to provide protection from ingested toxins, whereas homometabolous Lepidoptera metabolize such toxins more efficiently. Migratory grasshoppers, Melanoplus sanguinipes Fab. (Acrididae), eliminated the thiophene alpha-terthienyl in their feces more quickly and metabolized it to a lesser degree than did variegated cutworms, Peridroma saucia Hubner (Noctuidae). Xanthotoxin, a phototoxic linear furanocoumarin, and digitoxin, a cardiac glycoside, underwent similar metabolic modification in both species. Rates of fecal elimination of xanthotoxin were similar, whereas digitoxin was voided more rapidly by P. saucia. Overall, our results fail to provide convincing evidence in support of the test hypothesis because the two species investigated do not differ markedly in the manner in which they metabolize and eliminate the allelochemicals utilized in these studies.