Campaign Diary: Caterpillars turned my cherry tree into a ghost | Insects

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FOn the other side of the vegetable garden is a ghost tree, a solarized photograph of a tree against a green background of sycamore and hawthorn. Every year the leafy tips of this bird cherry are covered with the stretched spun tents of the caterpillars of the ermine moth, Yponomeuta evonymella. This year, the entire tree is encased in pale, shiny opaque cling film.

I look at its trunks and they are silver all the way up. The work of caterpillars encased leafy lichens, imprisoned fallen budding cherries, and wrapped trunks in poisonous silk. It’s weird and fascinating, and more of a spectacle than most years; moths reproduce in cycles of boom and bust.

The approaching twin trunks have formed a cleft, and this is filled with white pupae in neat parallel lines, like schools of fish swimming in the same direction. I press the taut silk with my fingertips and it bounces, a few bodies still moving below, turning as they go. Where I break it are layers and layers of gauze. Caterpillar droppings collected in tide lines, peppercorns colored dark brown to tan to buff.

Under the tree, a table and chairs have been wrapped together and a row of rosemary bushes are entangled in film. Blue tits smash their way through the bare branches above, picking off any unprotected caterpillars. Flying between birdhouse and cherry tree, they raise their brood on this easy bounty.

Inside their web, the caterpillars pupate. In a week, a wave of leaves will appear on the ends of the branches. No longer chewed, the tree recovers unscathed; it would not be in the butterflies’ interest to kill their host. After a short pupation, several thousand moths will emerge, their thin white wings dotted with five rows of black dots.

Adult moths have another defensive strategy. Because they are deaf, they cannot listen to approaching bats, so they produce a continuous series of ultrasonic clicks from their hind wings, mimicking those of poisonous butterflies.

Soon the adults will emerge and when I do my weekly light trap moth count there will be a dramatic increase in the number recorded.

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