Janalee Cadwell of the University of Oklahoma, US, has been investigating South American frogs whose poisonous secretions are used to tip arrows and darts. Her researches have led to the conclusion that these amphibians are toxic not because of some biochemical synthesis within them, but because they eat a deadly diet of ants which contain alkaloids. These poisonous frogs hunt openly in the day whereas non-toxic frogs are cryptically coloured and nocturnal. The idea that these frogs generate their own poison had been in doubt for sometime as frogs raised in captivity on a mixed diet do not develop toxic skin ( The Economist , December 21, 1996).