Net of the Bird-Cherry Ermine (Yponomeuta evonymella)

Dear Readers, I’ve written about the Bird-Cherry Ermine moth before, but during a walk with my friend L today I finally saw some of the tiny moths emerging. We were in Cherry Tree Wood in East Finchley – it used to be known as Dirthouse Wood because  nightsoil and horse manure used to be collected at the site of the Old White Lion pub just across the road, but Cherry Tree Wood, presumably referring to the Bird Cherry trees, is obviously much more inviting.

Bird Cherries in Flower

I love the way that the flowers of the Bird Cherry look like fireworks exploding out of the tree, but I honestly don’t begrudge the Ermine Moth caterpillars their meal. Some years there are a lot of them, but in other years they’re barely there. And just look how pretty they are when they hatch.

Here’s a rather clearer photo:

Bird-Cherry Ermine (Photo Ivar Leidus, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0&gt;, via Wikimedia Commons)

These tiny moths are nocturnal, and at this time are subject to predation by bats. Furthermore, they’re completely deaf, so aren’t able to hear any incoming predators. However, an interesting study has shown that Bird Cherry Ermine moths, and some other closely-related species, produce ultrasound clicks during flight that are similar to those used by tiger moths. But why? Tiger moths contain compounds which are distasteful to birds and bats. During the day, their bright colouration means that birds avoid them, but at night they produce clicks that warn bats not to eat them. The Bird Cherry tree that the caterpillar feeds on contains compounds that can be converted to hydrogen cyanide during the digestion process, so it appears that the Bird Cherry Ermine moths are also producing warning sounds. Furthermore, these sounds are faint enough so that they won’t advertise the presence of the moths to the bats, but loud enough that the bat can hear them before it actually chomps the moth.

You can read the whole paper here, and very fascinating it is too (plus it’s rather more accessible to the non-specialist than many research articles). As the authors say, we know so little about the acoustic arms race between bats and flying insects that’s going on in the skies.