Animals with bright colors are often a warning of inedibility to potential predators. Sometimes, as a ruse, perfectly tasty creatures look like those who don’t make a decent meal. English entomologist Henry Walter Bates called such deceivers “mockers.”
English naturalist Alfred Russel Wallace contemplated evolution at the same time Charles Darwin did. The two published their musings on natural selection contemporaneously.
Among his extensive fieldwork, Wallace avidly collected insects. The beautifully colored Pachyrhynchus weevils of eastern Asia and Australia were in Wallace’s collection.
Wallace considered these beetles hazardous: not because they were poisonous, but because their body armor would be impossible for predators to chew. (Wallace found this out firsthand when he tried to pin Pachyrhynchus weevils to one of his collection boards. Unable to do so, Wallace had to resort to a drill for the chore. 150 years after Wallace proposed Pachyrhynchus as bite-proof, researchers confirmed that these weevils were not in the least toxic.) And so they are (impossible to chew). A bite of this beetle by a bird is enough to spit the bug out like it was a stone.
Only the adults are tough as nails. Young weevils are quite digestible. Their shells only toughen after 2 months. Hence, juvenile Pachyrhynchus are mockers of their future selves.