Nikonian72 wrote:
Monarch caterpillars eat only milkweed, concentrating the milkweed toxin in their skin, which has to be replaced every time they molt. The adult Monarch also has toxin in its skin. This toxin acts like natural Ipecac, causing birds to retch almost immediately after eating caterpillar or butterfly. Birds learn quite quickly to avoid brightly striped caterpillars and orange colored butterflies.