Sci: Keeping pill bugs

I apologise for the gap, but I  had two books to complete.

For several years, I had a small combination isopod-home-and-compost-heap sitting on my desk. This began as a test of an idea for my school students (if you came in part-way through this book, I was for some years a ‘visiting scientist’ in a local primary school). I wanted an easy way to set up individual pill-bug farms, and I worked with groups of three or four students to get their farms started. Let’s begin with my deluxe version, based on a clear polystyrene box that Ferrero Rocher chocolates come in.

A desktop compost heap which ran for two years.

For large-scale production in the school, we used thin plastic ‘takeaway food’ containers, and did the following, using sand from the school’s sandpit, and part of my home garden compost heap. Still, the clear chocolate box is better.

I take the box out to add extra leaves and sometimes a bit of water, but I often get the eggs or grubs of tiny flies called fungus gnats, and they can be a pest. Now you can work out why, most of the time, I leave the lid on when the box is inside.

A look inside: I used a dissecting needle to move the leaves aside to expose a resident. Inset: a clearer view

Instructions given to my students:

* Put about 6 to 10 mm of sand in the bottom and spread it out;

* Add just enough water to make the sand go dark (and note the colour difference);

* Get Peter to add some rotting litter (it may have germs, so he wears gloves);

* Using a brush and a tube, catch eight pill-bugs from the leaf litter from his garden;

* Add them to the container;

* Add some clean dead leaves for the pill bugs to eat;

* Put the lid on, and add a sticky label with your group’s names.

We also made five air holes in the lid with a needle. Those cheap containers split easily, but we drove all our holes through the label, which prevented splitting. After that, the students just needed to add water if the sand looked dry, and add leaves when the supply had dropped.

And that is how I invented the desktop compost heap. I have had one on my desk since then, and it is still doing well. At the time of writing, there is also a resident leech that has been parked there until I have time to photograph it. The pillbugs don’t seem to mind, and the leech emerges from the leaves to wave hungrily at me, each evening.

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