Sequestration of lichen compounds by lichen-feeding members of the Arctiidae (Lepidoptera)

A survey for the presence of sequestered lichen compounds in 103 wild-caught imagines representing eight different genera and 16 different species of the Arctiidae was conducted. Known lichen compounds were detected for the first time in 24 of the analyzed specimens (representing five different genera and 11 different species) based on their HPLC retention times and on their UV-absorption spectra. The anthraquinone parietin, the depside atranorin, as well as a hydrolytic cleavage product of the latter were among the lichen compounds most frequently detected in wild-caught imagines. The observed variation of sequestered lichen compounds in wild-caught imagines with unknown feeding history may be due to several reasons. Lack of lichen compounds in imagines may have been caused, for example, by larvae feeding on lichens with no or only minute amounts of phenolic products. The age of the specimens analyzed may also influence the results obtained. Avoidance of lichen compounds by selective feeding on those parts of lichen thalli that have no or little lichen products may be another reason for the lack of lichen compounds in imagines. Preliminary feeding experiments conducted with larvae ofEilema complana, for example, indicated that the larvae fed exclusively on the algal layer and cortex of the lichenCladonia pyxidata, whereas the medulla, which is rich in fumarprotocetrarie acid, was avoided. As expected, imagines hatching from the larvae were free of this lichen compound. Any ecological role of the sequestered lichen compounds for the herbivores is unknown. It is possible, however, that sequestered lichen compounds may be utilized for the chemical defense of arctiid moths or against microbial pathogens.