DangerMoth! – Hairy Caterpillars - Super Villains or Super Heroes?

Recent press coverage of the Brown-tail Moth may have caused you alarm at the prospect of an imminent invasion of some killer insect plague. A little caution is required, though. Of the wildlife, possibly, but also how you choose to approach it.

There are many hairy caterpillars resident in this country and have been here for thousands of years. Most are harmless, but as the caterpillar, or larval form, of butterflies, moths and sawflies they can sometimes suddenly appear in quite large numbers and cause some concern.

Usually this starts in early summer when they have emerged from eggs laid earlier by flying adults in the autumn or spring.

They can be seen feeding on hedgerows and field margins, but also they can gather on suitable plants in parks or peoples gardens in a large mass under a web like cocoon.

They have to feed and fatten up fast and try and avoid being picked off by birds in the process, hence the hairs and sometimes bright “alarm” colours to warn the birds off.

They then turn into the next, apparently dormant, stage of pupa or chrysalis. Often, these can look like a curled up leaf or a bird dropping on, or hanging underneath, a leaf.

During this time, though, enormous chemical and physical changes are taking place in which the caterpillar completely breakdowns and re-arranges its body form.

From this they will emerges later in the year as a fully formed, but short lived, adult butterfly or moth. Their task is to fly, avoid predators, find a mate and breed to begin the cycle over again.

Take a look at these fairly commonplace possible candidates to begin with.

                                                                                                                    They are hairy and completely harmless. They are working hard to turn themselves into beautiful Small Tortoiseshell or Peacock butterflies that you may well delight in finding in your garden later in the year.

You don’t have to handle them, and probably best to let them go about their business, but if you do touch them they won’t do you any harm.

The next examples are fairly common, hairy and prickly so best not to handle them if you can avoid it. But these too are otherwise harmless and will eventually, if left alone, turn into Scarlet Tiger or Pale Tussock moths.

These next caterpillars can cause some people an allergic reaction if they are handled or their cocoon is interfered with. The hairs of the Oak Processionary Moth, an occasional visitor to southern counties, and Brown-tail moths can break off and float freely when disturbed. People have reported rashes and eye irritation and, very rarely, more severe reactions.

They can be found feeding under communal webs on Hawthorn or Blackthorn hedges. So do leave them well alone until they pupate and neither you nor they should come to any harm.

We can all get unnecessarily alarmed by their seemingly strange appearance of “creepy-crawly” things, but they are just doing what they have done for many thousands of years before we all came along and started interfering with them.

Many butterfly and moth species are in decline for many reasons, not all of them understood. Some species are so rare as to be legally protected from interference during all of their life stages, including as caterpillars.

So before you panic and call in the pest controllers, take a little time to find out what it is you have seen and how best to deal with it. After all, it is not necessary to kill something just because you may have been frightened of it by alarmist coverage in the media.

Consider for a moment just how elaborate are the life stages of theses insects. How fragile is their existence at every stage, how vulnerable to predation they are and why they need their hairs as a form of self protection.

So, please put the “Shock Horror” scare stories aside this summer and take up the “WOW – Amazing” one instead and before taking out the insecticide spray consider the option of not interfering with or damaging them unless it is really necessary.

They will soon enough, in a few days or weeks, turn into pupae and eventually into attractive adult insects to help pollinate flowers, provide food for birds and in the meantime bring a little colour and delight into our lives.

Here are some ways to check out first what you may have seen: -

Try and identify and take a note of the plant on which it is feeding as this can be a favoured food plant often associated with a particular type of larva.

You can look at the numerous photographs of larvae on this useful website – What’s this caterpillar?

Another helpful site is the UK Moths search facility, which is useful if you have some idea already what you have seen and want it confirmed.

If you can’t ID the larvae from these, see if you can find a copy of Caterpillars of the British Isles by Jim Porter ISBN 0-670-87509-0 at your local library. This has many well set out photographs of nearly the entire species resident in the UK.

Failing these, contact us and send us a digital photograph using our online enquiry form, and we will try to help, but we can’t promise to get back to you immediately.

If you are still concerned about the caterpillars you have seen, or think you may have a recognised pest species in your home, try calling the Wiltshire Council for advice from their public protection department on 0300 456 0100 or visit their website