American researchers have discovered that a chemical exuded by the colourful skin of poison frogs is a superb mosquito repellent.

Paul Weldon, from the Smithsonian Institution, Virginia, and his colleagues investigated the effects on mosquitoes of a highly toxic alkaloid, one of a class of pumiliotoxins, which they extracted from the skins of tropical poison frogs (dendrobatids).

The team found that most yellow fever mosquitoes steered clear of membranes or wires coated with the pumiliotoxin, and some of those who landed subsequently rolled onto their backs and died. Very little mosquito repellent was required to have a toxic effect, far less than is naturally found on the frog’s skin, and the natural pumiliotoxin was far more toxic to invaders than its synthetic enantiomer, the mirror image form of the molecule.