What's this? 26th June 2016

This week my wife has been participating in a small exhibition of paintings and jewellery at a farmhouse near Swerford in Oxfordshire. A couple of evenings ago she arrived home to show me a picture on her i-phone and asking 'Do you know what this is? It was in one of the bushes in the garden where the exhibition is being held'

I had a look and was pleasantly surprised to see that there before me was the unmistakeable image of a Puss Moth caterpillar. Without much persuading I suggested I would come over tomorrow and have a look for myself as I had not seen a Puss Moth caterpillar in years.

Adult Puss Moths have a beautiful grey and white marbled appearance and are so called because of the furry coating over their head, body and legs

The next afternoon I went over to the farmhouse and surveyed the bush which was in fact a heavily pruned willow no more than five feet high. 

The Willow bush harbouring at least five Puss Moth caterpillars

At first I could see nothing but as is usual in such cases it took a little while to get my eye attuned and then as if by magic I found one of the beautifully camouflaged caterpillars and then another and in the end there were five on just this small bush of willow.

Puss Moth caterpillars or larvae if you wish to be pedantic are arguably one of the strangest, quirky and most striking of all moth or butterfly larvae, with what appears to be a large square head and two prominent spikes at the rear of the body. Prod the caterpillar and two fine red threads, called flagellae come out of the ends of the grey and black spikes whilst the front end of the caterpillar convulses so the head is raised, pointed towards you and at the same time drawn back into the thorax . The head when withdrawn is surrounded by a pinkish red square with two prominent black false eyes meant to add to the deterrent effect.

If all this is not enough of a deterrent the caterpillar, as a last resort is also capable of squirting formic acid from its thorax. Not enough to harm a human but probably enough to get into and irritate the eyes of a smaller predator such as a bird or rodent.

The larvae emerges from the egg as a tiny black caterpillar and then goes through several stages known as instars where it gradually grows until it becomes green with a prominent black saddle over its back. The two whip like grey and black spikes at the rear are really modified claspers and when threatened the caterpillar spins a fine red thread from each spike and waves them around to enhance its fierce appearance. 

When it is ready to pupate the caterpillar turns orange and then purple, before spinning a cocoon of silk and camouflaging this with bits of bark. The cocooon is one of the strongest of any moth in Britain and the adult moth will emerge next Spring to complete the life cycle