Up by the car park at the entrance several ragwort plants are in bloom. They are covered in these bright yellow and black striped caterpillars which are munching away in an alarming fashion.
The charity Buglife says that many insects - bees, moths, butterflies, wasps and other invertebrates are totally dependent on ragwort for food.
Looking them up I found out that they are the caterpillars of the cinnabar moth. We know that ragwort is poisonous to horses and cattle, though they would have to eat 25% of their body weight in ragwort to make them seriously ill, but as we're not keeping animals we didn't see any reason to remove them. I was very interested to find out how the cinnabar moth makes use of the ragwort poison to protect itself,
The cinnabar moth lays its eggs in large batches on the lower leaves of ragwort and when the caterpillars emerge (June to August) they eat their way up the plant. In their early stages the caterpillars are prone to attack from many insects but as they progress they store poison from their host plant in their bodies making them unpalatable to birds and they advertise this fact with bold orange and black stripes.
In August, the mature caterpillars leave the host plant and spin a cocoon in which to hibernate in the soil, at this stage they are sometimes eaten by moles.
They emerge the following summer (May to July) as adult moths when their red and black wings still advertise the poisons they contain making them safe from attack by birds.
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| Cinnabar moth - photo by David Chapman |
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