The Delightful December Moth

The December Moth, Poecilocampa populi, is found all over the UK. Because it is more resistant to cold than most other moths, the adults are common in parks, gardens and woodland during late autumn and winter.

Marvellous Moths

Many people don’t give moths a lot of thought. Most have incredible camouflage and they often fly at night, so we don’t tend to see them. When we do think of moths, it may be just as a kind of drab butterfly that sometimes eats our clothes. In reality, there is much more to the world of moths than we might think, and they are very important to our world.

Moths, together with butterflies, belong to the group of insects called the Lepidoptera (“scaly wings”) There are over 2,500 species of moth in the UK and only a very few will eat our clothes. Many of these moths are beautiful, either because of their spectacular colouration or because of the way their camouflage enables them to blend into their habitat.

Moths are important in ecosystems. Both adult moths and their caterpillars play crucial roles in food chains, feeding on plants and being eaten by bats, birds and other animals. It is estimated that about 35 million caterpillars are eaten by blue tit chicks every year! Moths also play a vital part in the reproduction of several plant species because of their role as pollinators.

‘Like a moth to a flame’

December moth showing black and brown colouration.

Adult December moths are night-flying and, like other moths, they are attracted to light at night. Entomologists are still not sure exactly why this is. One theory is that moths use the moon to navigate and can mistake a light for the moon. Another is that they normally fly with the lighter sky above them and a light source near the ground confuses them into flying downwards. This would explain why they are attracted to street lights and lit windows, and also why they fly downwards into light traps.

December moth, Poecilocampa populi. Photo: Ben Sale CC-BY 2.0

Life Cycle of the December Moth

Larvae and pupae of the December moth
Larvae and pupae of the December Moth in the HOPE Collection at the Museum

While adult December Moths can be found throughout autumn and winter, each individual is short-lived and does not feed. They mate and the females lay their eggs on food plants. The eggs overwinter and the larvae only emerge the following spring. These caterpillars can be found throughout spring and summer taking advantage of the new growth of leaves. They are active voracious feeders at this time and will eat the leaves of a wide range of deciduous trees. When they have gained enough weight, they pupate, with the adult moths emerging to repeat the cycle in late summer and autumn.

Pinned adult DEcember moths in the HOPE collection.

Moths are important indicator species: their presence tells us about the overall health of the environment.  Unfortunately, what moth populations seem to be telling us is that something is wrong.

Comparing the number and type of moths found in Britain today with those recorded in historic insect collections like the HOPE Collection at the Oxford University Museum of Natural History, shows us that moths have declined by about 40% in southern Britain. Over 60 moth species have become extinct in the UK over the last century and many more are at risk of disappearing forever.

Other animal species which rely on moths as food are also suffering, including a decline in bats flying over farmland and reduced numbers of cuckoos, which specialise in feeding on hairy moth caterpillars which other birds tend to avoid.

We need to do more research to fully understand exactly why moth species are declining in Britain, but it is likely to be because of a combination of factors including loss of habitat, farming practices such as clearing hedgerows and the use of pesticides, and climate change.

Adult December moths in the HOPE Collection

Ways we can help moths

Fortunately, many moth species under threat are found in parks and gardens, so we can all do things to help:

  • Not over-tidying gardens; a more natural look is much better for insects.
  • Growing a wide variety of large and small flowering plants and, if you have room, shrubs and trees.
  • Avoiding the use of weed killers and insecticides.
  • Reducing light pollution from outdoor lights
  • Reducing your carbon footprint, for example, by driving less and walking or cycling more.

If you enjoyed reading about the December Moth, you might like this post by Ben on Raising Poplar Hawk Moths.

Insect super powers: surviving the winter

Insects have some really cool super powers and surviving extreme temperatures is one of them!  Have you ever wondered how insects manage to survive in the cold winter months? 

In the Summer, insects are all around us but in Winter they seem to disappear.  Where do they go and how do they survive the extremes of winter?  Unlike us, insects can’t put on a coat, hat and gloves or turn up the central heating!  With such a small body size, they could easily freeze as the temperature drops but they have some pretty cool ways of making sure their species continues to the next generation.

Take a look at these ideas. Who you think is right? Do you have a different idea?

Zane, Zeb, Zora and Zip are all right!

Strategy 1: Diapause

This is similar to mammalian hibernation where adults survive the winter in a state of torpor or dormancy.  Insects find suitable places to spend the winter such as holes in dead wood, under leaf litter or inside sheds and other buildings. They then become inactive, their heart rate slows right down and some insects even produce anti-freeze chemicals to stop them from freezing. 

Here are some insect species that undergo diapause:

During the Winter, only the queen bumblebee survives and amazingly all the other bumblebees die.  The queen spends the winter in an underground burrow already carrying the eggs that will be the next generation.

Butterflies such as Peacocks, Brimstones and Red Admirals shelter in garden sheds during diapause.  Sometimes you can find them inside houses – do not disturb!

Ladybirds huddle together in groups, for example, under bark of trees.

Strategy 2: Seasonal Lifecycles

The adult form of many insect species will not survive the winter but one of the other stages of their lifecycle (either the eggs, larvae or chrysalises) will survive by keeping warm in places such as leaf litter, under bark or in long grass waiting to be activated by the warmth of the sun in the spring.

The larval stage of the Stag Beetle and the Purple Emperor butterfly survive the winter, but the adults die.

Strategy 3: Migration

A few British insects such as the Painted Lady and Clouded Yellow butterflies migrate to Africa for the Winter.  Individual Painted Ladies have been recorded making journeys of nearly 2,500 miles. Unlike birds, the same individuals do not make the return journey the following year – that journey is made by a new generation.

Strategy 4:  Remain Active

Lots of insects do, in fact, remain active in the winter.  It is just harder to find them because they are keeping warm under leaf litter, amongst long grass or, in the case of aquatic insects, under water.  Most insects who do this are just feeding and waiting for the Spring when they can find a mate and reproduce but some species, such as Winter Moths and December Moths, reproduce during the winter months.

We would love to see your photos or hear about insects you have seen this Winter. What can you find in your garden or local outside spaces?  Be careful not to disturb them too much! You can tell us about it using the form on our Contact Us page, or email us at hopelearning@oum.ox.ac.uk.