Moths

One of the wonderful things about moths is a lot of the beautiful ones can be seen in your own back garden, which is unsurprising when you consider there are around 2,500 species of moth in the UK! All you have to do is take the time to attract them.

Attracting moths

There are several ways of doing this and not all involve staying up all night! For example pheromone lures can be used. Pheromone lures are synthetically made in labs and are designed to fool male moths into thinking there is a female around. Many male moths such as emperor moths will be attracted to the female’s pheromones during the day, so placing a pheromone lure in your own back garden can attract males from miles away. Assembling can also be used. This is where a female is reared and taken out in a net bag. The male is then attracted to the pheromones the female is releasing. Of course this takes a lot more effort than using laboratory made pheromones!

Moths are also attracted to fermented fruit or sap runs, this can also be synthesised by using a technique called sugaring. This is where mixtures based on black treacle are boiled up and painted on trees. Rum or beer can also be added to these mixtures to help attract moths from further away.

Wine roping is another technique. Rope is soaked in a solution of red wine and white sugar and hung on foliage at dusk.

Of course the most widely used method of attracting moths is light-trapping. Not all species of moth will come to light but many will, enough to keep you interested at any rate! Light-trapping is relatively inexpensive and very easy. A light trap is switched on at dusk and turned off again at dawn. The moths that have fallen into the trap overnight settle down on the egg boxes in the bottom of the trap and are mostly easy to catch the next morning when the trap is checked. These moths can then be identified and released unharmed. We find it is best to leave them in the trap during the day and let them fly away of their own accord the following evening. This leaves them less vulnerable to predators.

Why moths are attracted to light

One of the most frequently asked questions about moths is “why are they attracted to light?” Unfortunately there is no definitive answer to this question. Although scientists around the world have come up with a handful of theories.

One theory is that they use the moon to navigate and the presence of artificial lights disrupts their navigation. However some entomologists say this would only make sense in species which migrate. Many moths do not attempt to migrate and therefore would not need to use the moon to navigate the distances they fly.

Another theory is the escape route mechanism. If they are disturbed they fly towards the light (usually up out of a bush) rather than towards the dark (usually down towards the ground). However this would result in moths only flying towards light when disturbed and this does not seem to be the case.

Another theory is that moths mistake artificial light for the light given off by female pheromones. Moth pheromones are luminescent, which means they glow very faintly. A US entomologist, Philip Callahan discovered that some of the frequencies of light given off by a burning candle are the same as the frequencies given off by the female’s pheromones. However, UV light does not share these frequencies and they also attract moths, so in the case of UV light this must not be true.

Moths and bats

Moths are predated by a variety of species. However, their most interesting predator-prey relationship is with bats. Bats and moths have been locked in an evolutionary arms race which has lead moths to develop interesting ways to avoid predation by bats.

Some moths can hear the echolocation calls from bats allowing them to hear when a bat is close by and avoid it. Some bats have been found to use lower frequencies. This is believed to be because moths are not as sensitive to these frequencies giving the bats the upper hand once more. Other moths can click in a way that mimics bat echolocation, this disrupts the bat’s echolocation and allows the moth to escape. Other less advanced species simply use erratic flight patterns to make themselves harder to chase.

What can you do?

Making your garden moth-friendly is very easy, and is also good for other wildlife as well.

• Leave fallen leaves and other plant debris at the back of borders where moths can hide away over winter
• Use fewer pesticides and herbicides in the garden
• Make space for a wild area where the grass can be left to grow long over the winter and self sown weeds will provide breeding habitat for many moths
• A small tree or shrub as well as a lawn and flower beds will make the garden better for moths
• Keep your garden green. Moths can’t live on decking or gravel
• Do some moth trapping in your back garden and send the information to your county moth recorder