DO CYANOGENIC GLYCOSIDES AND PYRROLIZIDINE ALKALOIDS PROVIDE SOME BUTTERFLIES WITH A CHEMICAL DEFENSE AGAINST THEIR BIRD PREDATORS? A DIFFERENT POINT OF VIEW

It is a generally accepted concept that the secondary plant metabolites - the cyanogenic glycosides, and the pyrrolizidine alkaloids are the main chemical compounds providing Heliconiinae, Acraeinae, Ithomiinae, the day-flaying moths Zygaenidae, and other aposematic butterflies with a potent chemical defense against their main vertebrate predators, the insectivorous birds. This author does not agree with this concept and presents a different point of view. His thesis is based on (1) the limited ability of birds to taste, (2) the inability of birds to taste via ʹbeak mark tastingʹ or simple pecking, and (3) on voluminous data and arguments in the extensive literature, dealing with many aspects of interest concerning secondary plant metabolites and their role in the chemical defense of butterflies, which do not support the generally accepted concept. In this paper are assembled the most important and convincing information opposing the view that these various chemical compounds provide butterflies with a chemical defense against bird predators. A revision of the currently accepted concept is suggested.