Caterpillars may be poisonous (toxic to touch) or venomous (injecting poison through a sting). They can leak acids, have poisonous hairs, feed on poisonous plants like milkweed and store poison inside their bodies.
While most of these venomous bugs exist in more extreme climates than the UK, several of these species can be found in our own back gardens. A recent scare concerning a swarm of caterpillars ‘invading’ the UK told of the brown-tail moth, spotted in southern England, whose toxic hairs cause rashes and disrupt regular breathing with severe reactions resulting in asthma.
Another caterpillar with toxic hairs is the oak processionary moth, which is one of the few species that is poisonous to both humans and animals. The hairs along the body of this caterpillar hold toxins that cause irritation to the eyes and throat as well as rashes on the skin.
The most venomous caterpillar in the world, identified in the Guiness Book of World Records, is the lonomia obliqua, a species of moth from South America. This caterpillar has been responsible for several deaths, especially in Brazil. This is because its venom contains anti-clotting agents which can cause internal hemorrhaging in its victims. It was not known that caterpillars could produce venom capable of killing a human being prior to this discovery.
Considering this, the lonomia obliqua is not the only caterpillar with this lethal reputation.
The saddleback caterpillar, named after the green saddle-shaped patch on its back, is another species of caterpillar with venom that has extraordinary potential. Its venom targets and kills blood cells, making its sting a very real threat to a human being.
These poisonous caterpillars are quite unremarkable as fully developed moths, as they shed their poisonous hairs in the cocoon, leaving their toxicity behind them as they emerge as adult moths and fulfil their full metaphorical potential.