Mate choice in the polymorphic African swallowtail butterfly, Papilio dardanus: Male-like females may avoid sexual harassment

Papilio dardanus, the African swallowtail butterfly, is a species with a female-limited polymorphism for wing colour pattern. Females of the subspecies P. dardanus tibullus on Pemba Island, Tanzania, occur as three genetically distinct morphs; a black and white Batesian mimic (hippocoonides), a black and yellow male-like morph (trimeni) and a morph that is similar to trimeni but with orange wing-patches (lamborni). Male mate choice was studied by recording the responses of wild males first to simultaneously presented pairs of pinned dead females, second, in sequential choice tests where only a single female was presented at a time, and third, during focal follows of wild females. From a distance males consistently preferred the Batesian mimic, hippocoonides, above the andromorph, trimeni, and trimeni above the third morph lamborni. Preference correlated both with the frequencies of the morphs and their colour, the more common brighter morphs being preferred. It is proposed that the hippocoonides, trimeni and possibly also lamborni morphs are maintained in a stable polymorphism by different frequency-dependent selective advantages. The morph hippocoonides supposedly have low predation because of Batesian mimicry (frequency-dependent) but suffer costly harassment by males, whereas trimeni avoid this harassment through male mimicry (possibly also a frequency-dependent advantage) but are not protected from predators. The third morph, lamborni, which suffers the lowest levels of harassment, may gain this advantage by mimicking the orange coloration of ageing males. © 1994 The Association for the Study of Animal Behaviour.