Butterfly males leave a stinky parting gift with mates that deters further suitors
The chemical compound saves the female from unwanted harassment and guarantees his paternity
Researchers have found that males of the postman butterfly, the species Heliconius melpomene, produce a strongly scented chemical in their genitals that they leave with the female after mating.
The brightly coloured butterfly is found throughout Central and South America. Males produce a compound called ocimene in their genitals, which they pass along to females as a nuptial gift with sperm during mating.
The female stores the sperm, but releases the strong, musty smell into the air. The pungent smell, which can last for weeks, deters other males from pursuing the female. This guarantees the male that he will be the father of the females offspring, and allows the female to avoid unwanted attention from males when she has already mated.
Flowers make the same chemical
Kathleen Darragh, working at the Department of Zoology at Cambridge University in England, and her colleagues identified the gene that is responsible for the production of this compound.
This was something of a surprise as the same chemical is produced by plants, and it had been suspected that the butterflies sequestered the chemical from those plants. But the team found that butterflies had evolved the capacity to make the chemical independently of plants.
Flowers make it to attract butterflies for pollination. The fact that the same compound produces a smell that repels in a mating context, but attracts for feeding presents a paradox. Darragh said how the chemical works may be 'context dependent'. The flower is producing other scents at the same time, so the butterfly is not just smelling the ocimene, but that it makes up part of a complex floral bouquet that can be attractive, despite its ingredients.