When I noticed, a few days ago, that some leaves on a young cherry were being grazed, I didn’t give it much thought. It’s the time of year when caterpillars are everywhere and leaves are naturally heading into decline.
But, later on, a slimey black splodge on one of the cherry leaves made me look a little closer. And there was my first cherry slug worm. I’d learnt about cherry slug worms being a pest almost all over the world, but I had never seen one in the flesh, so to speak.
Cherry slug worms are the larvae of a sawfly – Caliroa cerasi. They coat themselves in shiney bluish-black gloop to put birds off from eating them. This gloop works so well that the slug-worms confidently feed in broad daylight on the upper surfaces of leaves. There they eat away all the flesh, just leaving a skeleton of leaf veins.
Cherry slug worms are also supposed to be quite happy eating hawthorn leaves, so after these two had had their photos taken, I moved them to a hawthorn bush. If they’re unlucky, they’ll be parasitised by a wasp; if I’m unlucky, they’ll pupate in the litter under the bush and emerge as flies to lay eggs and make more slug-worms next year!