The miners

You wouldn’t imagine it, but the Danish insect world is full of countless miners. Not, of course, the kind that dig for gold, but the larvae of different insects that are so small that they can dig, or more correctly, chew tunnels through the flesh between the surface and the underside of a leaf – this is the way they feed. These kinds of tunnel diggers are called miners and they can be found in the leaves of hundreds of species of trees and flowering plants. Miners are usually the larvae of butterflies and flies, but beetles and other insects are also sometimes at work.

When the tunnels are formed by eating, you would think that they had a fairly random appearance, but this is not the case. The larvae eat in such different ways, that you can identify the species from their tunnels, even though the insects left them a long time ago. Some of  them are long, intricated labyrinths, others look like large galleries where it looks as if the larva has tried to excavate a ballroom.

If you look at a “mine” under a magnifying glass, you will see lots of small, black grains. This is called frass – a scientific name for larva droppings. You can also identify miners from the pattern of the droppings the larva has left in the tunnels.