PYRROLIZIDINE ALKALOIDS IN ARCTIID MOTHS (LEP) WITH A DISCUSSION ON HOST PLANT RELATIONSHIPS AND THE ROLE OF THESE SECONDARY PLANT-SUBSTANCES IN THE ARCTIIDAE

Pyrrolizidine alkaloids (PA) have been identified in six species of Arctiidae reared on Senecio and Crotalaria. These include senecionine, seneciphylline, integerrimine, jacobine, jacozine, jacoline, jaconine and a metabolite (C15H25NO5) from Senecio, and monocrotaline, trichodesmine and crispatine from Crotalaria. The all‐red aberration of Tyria jacobaeae (var. conyi) contained much less of the metabolite than normal examples of this species. Female Spilosoma lutea reared on the same plants of S. jacobaea contained markedly more jacobine and jacoline than die males. Host plant relationships and secondary plant substances are discussed. It is suggested that the Arctiid moths' own deterrent secretions, directed against vertebrate predators, pre‐adapts them for feeding on foliage likewise protected against large herbivores by toxic secondary plant substances such as cardenolides and pyrrolizidine alkaloids. These latter substances are more toxic to vertebrate than to insect herbivores, and their dual function of deterrent and insect aphrodisiac puts a premium on their sequestration and storage once a species has achieved the initial steps, and occupied the plant niche concerned. It is further suggested that the polyphagous habits of the Arctiidae result in a more equitable distribution of die secondary plant substances within the Mullerian complex concerned, thus providing a generalized warning message for the potential vertebrate predator. Copyright © 1979, Wiley Blackwell. All rights reserved