Sarah Ladbrook, of Balclutha School, asks :-

Why are there so many different types of worms?

Trish Fraser, a soil scientist with Crop and Food Research at Lincoln, responded.

There are lots of different types of worms, each living in different environments so that they have less competition for the food sources available. For example, there are earthworms (which live in soil), compost worms (which live in compost heaps), flatworms (which live on top of the soil) and tape worms (which usually live inside animals). Each of these creatures eat different foods and carry out different functions.

If we take a closer look at each of these worms we can divide them up further. In the case of earthworms for example we have 197 different earthworm species in New Zealand, 179 of which are natives and 18 imports, but they can be broadly described as being of three different types. Some live close to the soil surface, others live a little deeper down in the topsoil, and still others live in really deep burrows that may go as far as three metres down into the soil.

Those that live near the soil surface help to mix dead plant material and animal manure back into the soil. The ones that live within the topsoil burrow through the soil creating channels that roots can follow and mixing the soil so that plants can find nutrients to help them grow.

Those living really deep inthe soil tend to come up to the surface and pull leaves and other surface litter material down into their burrows. They use the same burrows over and over again, so their activity can, for example, have a big effect on the way in which water flows into and through the soil.