What do moths eat? Feeding, life cycle and other facts

We have over a thousand moths in the UK! These fluttering insects perform an important role in our environment. But what fuels their activity?

Take a deeper look at what moths eat during their life cycle and how threats to moths affect this.

What do caterpillars and adult moths feed on?

What a moth feeds on comes down to the stage of its life cycle.

What do caterpillars eat?

Caterpillars (larvae) can feed on leaves, flowers, stems and roots. They have a labrum and mandibles that help them eat this solid material. The labrum is like an upper lip that holds the plant matter in position while the mandibles grasp and cut it.

Plants

The type of plant material that the caterpillars eat depends on the species. Some may be particular about their food source, while others are generalist eaters. They eat the outer layer of vegetation or, like the pea moth, eat the inside of plants. So it is best to shell your pea bean harvest carefully!

The oak processionary moth and pine processionary moth can strip a tree clean of leaves or needles, leaving the tree vulnerable. These are species that have been unintentionally introduced to the UK.

Underwater caterpillars feed on pondweed and waterweed. This aquatic species of moth, found in the UK, is called the water veneer (Acentria ephemerella). 

Fungi and lichens

Some moths in a family called Tineidae feed on fungi, lichens and other organic matter, such as rotting wood. Some moths, like the young gypsy moth, prefer to feed on leaves that are infected with fungal disease. 

Fabric

Moth larvae can also eat fabric. Only two species do this, namely the common clothes moth and the case-bearing clothes moth. Clothes moths eat natural fibres such as cotton, velvet, silk, wool, fur, leather and linen.

What do adult moths eat?

When a caterpillar turns into a moth, its mandibles are replaced by a  straw-like tube that coils up under the head when it isn't in use. When it's time to feed it coils out like a party blower and sucks up liquid.

Most moths have wings which give them the advantage of being able to lift off and scour a larger area for food. This food can come in the form of nectar from flowers, juices from rotting and fresh fruit or sap. 

Some moths do not feed at all because they survive for a number of days. During that time they mate and lay eggs. 

How climate change affects food chains

The life cycles of moths are carefully synchronised with those of their food plants. Mild winters can lead to flowers blooming and insects like moths emerging earlier than normal. This in turn has an impact on their predators (birds and bats) that rely on them as part of their diet.

Help us track the effects of weather and climate change on wildlife near you by joining Nature's Calendar. From leaf buds bursting to blackberries ripening, let us know what's happening near you and contribute to a biological record dating back to 1736.

Threats to UK moths

The State of Britain's Larger Moths 2021 suggests that larger moths have decreased in abundance and that, in general, ecologically specialised moths are not doing as well as generalist species. Those that were once common in gardens are in decline and include stout dart, garden tiger, blood-vein, white ermine, V-moth, golden plusia and garden dart. Moth species common in farmland and woodland are also experiencing similar losses, which in turn impacts food chains.

Moths are currently under threat and in decline due to:

• habitat loss
• intensive farming
• light pollution
• poor habitat management
• climate change and global warming
• pesticide- and pollution-induced environmental deterioration

The loss of veteran trees, wet areas, and traditional coppicing practices can lead to declines of moth species.

The expansion, protection, restoration, and creation of habitats with trees can go a long way to supporting moths. Trees planted together act as a sheltered corridor that can offer safe passage across farmland. Individual trees play their part too by providing places to lay eggs, leafy food and a supply of sugary nectar. 

You can do your bit for moths too by planting oak, hornbeam, hawthorn, apple, cherry, dogwood, birch and willow in your garden. You can also help moths and other species by tracking what's happening to nature near you.