Thursday, July 16, 2009
Many of the Common Ragwort plants in Ampthill Park are being decimated by these voracious brightly-coloured beasties at the moment. They are the larvae of the Cinnabar Moth (see 28th June post). It's well known that Ragwort causes destructive liver damage in horses and cattle when consumed in reasonable quantities. The animals will only eat them in the field if they're all but starving, but they can't detect the plant when it's been dried and incorporated in hay. The damage is caused by the presence of poisonous pyrrolidizine alkaloids. The great news for these caterpillars is that they are immune to these toxins which accumulate in their tissues as they devour their host plant. It means that many potential predators are going to give them a wide berth, which begs the question....when a single female Cinnabar Moth can lay up to 300 eggs, what is eating them? Why are we not being over-run by plagues of the things? Answers on a postcard.....!!