Year of Soils column by Tamás Salánki, March

They look just like white earthworms and are usually one to two centimetres long. They feed on dead organic matter and are found in most places on earth including the Alaskan snow, where they can be coloured blue or red.

One thing pot worms don’t much care for is warmth. That’s handy for me to know: in the laboratory, all I have to do to tease the worms out is slowly heat the soil samples they’re in. After that, I can count and classify them at my leisure.

I use a light microscope to look at the pot worms’ milky white bodies. All organs are visible and right there for me to scrutinize, as long as the worms keep wriggling and turning. It means that while other soil organisms have to be dead before you can study them properly, pot worms can only be classified alive. This makes it extremely interesting but also rather complicated. You never know in advance what kind of day a pot worm is going to have. A lazy worm can make my work drag on for ages, while an active specimen will find itself back in the teeming melee in no time.

To find ways of classifying even the most passive among the worms more quickly, pot worm researchers from around the globe meet up every two years. There are only 15-20 researchers worldwide who can classify pot worms. This makes pot worm taxonomists a considerably rarer species than the worms themselves. In the Netherlands, we have so far identified at least 75 different species, but in a single square metre of soil in a field in the province of Drenthe we once counted the staggering number of 163,812 pot worms.

It’s always a joy to discuss problem cases from my own collection with this handful of fellow pot worm fanatics. Behind the microscope or with a drink and a snack, time flies. Before we know it, our well-deserved night’s rest has evaporated: another casualty of our addiction.