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Do One Thing - Summer Term 2010

Field Studies Council has been working with the BBC and other partner organisations as part of the BBC Breathing Places campaign to provide help for schools to create space for plants and wildlife in school grounds.

Each term BBC Breathing Places Schools will provide you with a Do One Thing activity to help your pupils will learn about wildlife and plants and create a place where they can enjoy and explore nature. Once your school is registered, you will receive your free 'Do One thing' pack which includes materials and guidance. Help and advice will be available throughout the project.

The Do One thing this term is on ladybirds. This page looks at the life-cycle and food chain of another insect - the holly leaf-miner. It contains background information on the life-cycle and food chain plus worksheets for younger and older pupils. There is also more information about carrying out surveys of plants and animals.

Holly leaf-miners are widely distributed throughout the UK. Summer is an excellent time to look for the holly leaf-miner because their leaf mines will have reached maximum size and the adult flies are starting to emerge.

The food chain of the holly tree

Next time you walk past a holly tree look closely for leaf mines. They have been made by the holly leaf-miner. These insects feed by making a tunnel (called a mine) and eating the leaf from the inside. You can't see the leaf-miner from the outside of the leaf, but you can tell if they are alive by looking for mines on the upper surface of each holly leaf.

Look closely to see if there are any holes on the leaf mine. They give clues to what has happened to the insect inside.

Leaf mine with no hole
No hole - insect still inside
Leaf mine with large emergence hole
Large hole - adult has emerged
Leaf mine with tiny emergence hole
Tiny hole - eaten by wasp
Leaf mine with bird damage
Large flap - eaten by bird

Holly trees are producers. They capture the energy of the sun through the process of photoynthesis. Holly leaf-miners are primary consumers, as they eat holly leaves. Look out for a raised area on the surface of the holly leaf. Mines are mostly white and green in colour in the autumn, but they become more brown in the spring.

Some holly leaf-miners are eaten by birds, including blue tits. These birds are secondary consumers. Birds feed on the larvae by pecking the insect out of the mine. Look for a leaving a v-shaped tear on the leaf created by the beak of a bird.

Competing with blue tits are a number of parasites. For example, a parasitic wasp called Chrysocharis gemma inserts a single egg through the leaf into the body of the miner. The female adult wasp has a long spike on her abdomen which she uses to pierce the surface of the holly leaf and the soft body of the larva. She inserts each egg directly into the body of a holly leaf-miner. When the wasp larva hatches out, it eats the holly leaf-miner larva from the inside, and eventually kills it. The wasp larva then forms a shiny black pupa which lives in the mine. Later on the adult wasp emerges from the holly leaf. Look for very small neat hole on the mine.

Holly leaf-miner life cycle

Life cycle of the holly leaf-miner

Like ladybirds, holly leaf-miner flies go through four stages in their life cycle

  • egg
  • larva (plural = larvae)
  • pupa (plural = pupae)
  • adult fly

Female adult holly leaf-miner flies lay their eggs on holly leaves in June and July. Soon the eggs hatch and the larvae crawl out. They feed by making a tunnel (called a mine) and eating the leaf from the inside. You can't see the larvae from the outside of the leaf, but you can tell if they are alive by looking for mines on the upper surface of each holly leaf. The larvae carry on eating throughout the autumn and winter until the mines reach maximum size in March.

Larvae turn into pupae between March and May. Before it turns into a pupa, the larva prepares a thin triangular area on the underside of the leaf. In late May and June, the insect presses against this thin area, and the adult fliy emerges from the leaf. This leaves a large emergence hole (more than 1mm wide) underneath the leaf. The life cycle starts again as the female adult fly lays her eggs.

Not all holly leaf-miner larvae become adult flies. Some larvae are eaten by birds. Other larvae are killed by parasites.

What happened to the holly leaf-miner?

Holly trees are common in city squares and urban parks. In this investigation, students collect evidence of the food chain of the holly leaf-miner, studying energy flows through population numbers.

Animals are usually so transitory in feeding that it is impossible to assess the ecological impact of each species on its food source. However, the holly leaf-miner food chain provides an opportunity to study living organisms in the field and gain experience of ecological interactions in greater detail. Take care when collecting holly leaves - consider eye protection and gloves for pupils. For more background information for teachers, there was a useful article in School Science Review in 2006: What happened to the holly leaf-miner? (pdf, 1.6MB).

Learning resources for older pupils

Download all learning resources for older pupils (pdf, 457 kb)

Download Holly Leaf-Miner Food Chain PowerPoint presentation (268 kb)

Learning resources for younger pupils

Download all learning resources for younger pupils (pdf, 305 kb)

Download Holly Leaf-Miner Food Chain PowerPoint presentation (268 kb)

Carrying out surveys of plants and animals

For more general information on carrying out surveys, see the KS3 Science Fieldwork site. Advice on carrying out investigations in grassland and woodland can be found on the Urban Ecosystems site.