Hypolimnas bolina (L.), a mimic of danaid butterflies, and its model Euploea core (Cram.) store cardioactive substances

Abstract

Hypolimnas bolina is a sexually dimorphic nymphalid butterfly with a west to east distribution from Madagascar to Easter Island, and north to south from Japan to Australasia. To the west the female is monomorphic, mimicking species of the oriental and Australasian danaid genus Euploea¹. Eastwards H. bolina is frequently polymorphic and most forms are then non-mimetic. In areas where it resembles Euploea the butterfly has usually been designated a Batesian mimic. The supposed model feeds on Asclepiadaceae and Moraceae only, two families of plants of which various species possess emetic, toxic and purgative properties, whereas the foodplants of Hypolimnas include examples from eleven families, only a few of which are irritant or toxic². We now report that when the larva of H. bolina feeds on Ipomoea batatas, the butterfly stores cardio-active substances. Dried specimens of this butterfly, reared on Asystasia gangetica, a plant which does not contain these substances (Table 1), evoke no reaction on isolated rat heart, but living specimens produce a slight response. This indicates that in addition to material sequestered from foodplants, the butterfly itself secretes some type of cardioactive substance. A loss of intrinsic toxic qualities after death has been demonstrated in almost all aposematic model Lepidoptera³, whereas stored secondary plant substances can usually be recorded from an analysis of dried material.