Capsaicin β-glucoside was isolated from the feces of Helicoverpa armigera, H. assulta and H. zea that fed on capsaicin-supplemented artificial diet. The chemical structure was identified by NMR spectroscopic analysis as well as by enzymatic hydrolysis. The excretion rates of the glucoside were different among the three species; those in the two generalists, H. armigera and H. zea, were higher than in a specialist, H. assulta. UDP-glycosyltransferases (UGT) enzyme activities measured from the whole larval homogenate of the three species with capsaicin and UDP-glucose as substrates were also higher in the two generalists. Compared among five different larval tissues (labial glands, testes from male larvae, midgut, the Malpighian tubules, and fatbody) from the three species, the formation of the capsaicin glucoside by one or more UGT is high in the fat body of all the three species as expected, as well as in H. assulta Malpighian tubules. Optimization of the enzyme assay method is also described in detail. Although the lower excretion rate of the unaltered capsaicin in H. assulta indicates higher metabolic capacity toward capsaicin than in the other two generalists, the glucosylation per se seems to be insufficient to explain the decrease of capsaicin in the specialist, suggesting H. assulta might have another important mechanism to deal with capsaicin more specifically.