BRIGHT colours in the natural world are often a warning. In the case of tiger snakes, blue-ringed octopuses, arrow-poison frogs, hornets and many other species, the warning is that the animal carries toxins that will sicken or kill. Thus it was that Alfred Russel Wallace, co-inventor of the theory of natural selection and an avid insect collector, proposed that the beautifully coloured Pachyrhynchus weevils of eastern Asia and Australia were dangerous.
Yet, after spending hours trying to pin the weevils onto wooden boards in his collection and eventually having to use a drill for the chore, he suggested that the threat the beetles were warning of with their colours was not poison, but the presence of body armour that would be impossible for predators to chew. Now, 150 years after Wallace proposed this idea, Chung-Ping Lin and Lu-Yi Wang of the National Taiwan Normal University, in Taipei, have tested it. They show, in a paper in…Continue reading