The digestive system of Monarch butterflies protects them from poisonous milkweed latex eaten to make themselves poisonous to predators.


"Milkweed gets its name from a poisonous latex that exudes from its broken stem. This is so toxic that it can give a small animal a heart attack. The monarch butterfly, however, has developed an immunity to it. Its caterpillars nibble away at the leaves with impunity. But they do not digest the poison. Instead, they appropriate it and use it for their own purposes. In some way they are able to separate the toxin in the latex and store it unaltered in their bodies. This not only prevents them from succumbing to it, but makes them poisonous to any predator that might swallow them." (Attenborough 1995:70-71)

The Private Life of PlantsBBC BooksOctober 28, 2016
David Attenborough

MonarchDanaus plexippusSpecies