Tom Turpin
Professor of
Purdue University







Compost Piles are Alive With Arthropods

Any gardener worth their spinach or their creeping phlox possesses a compost pile. The compost pile is not the centerpiece of most gardens, but it does play a very important role. That is where the spent blossoms, pruned branches and pulled weeds are consigned.

But the compost pile does more than get things out of sight. It recycles them. This year's broccoli leaves become nutrients for next year's black-eyed Susans.

Good compost piles are more than a heap of dead plants. They are alive with the sounds of chewing. At least, they would be if we could hear the sounds of tiny mouthparts chowing down on discarded plant tissue. You see, compost piles are filled with tiny creatures that make their ecological living by feeding on dead stuff.

Most of these inhabitants of the compost pile are arthropods, creatures with exoskeletons and jointed legs. To be sure, earthworms are also common in compost and play an important role in breaking down the plant tissue. But by sheer numbers the arthropods dominate the compost heap.

Any sharp-eyed gardener turning over the compost will notice these creatures that shun the light. First there are literally millions of little white or gray things that seem to pop from place to place. These are tiny, wingless insects called collembola.

Collembola are sometimes called springtails. That name is based on a tail-like spring device that they use to catapult themselves from place to place. Collembola are the most common insects on the Earth, but because of their size and reclusive habits they go mostly unnoticed.

Sowbugs also are common in the heap. They are sometimes called roly polies or pillbugs. Sowbugs aren't insects, although most people regard them as such. They are crustaceans, as are crayfish, lobsters and crabs. Most crustaceans live in the water, but sowbugs can be found on the land doing the same thing as their water cousins - eating dead stuff.

Millipedes also find the compost pile to be a wonderful home. With two pairs of legs on each body segment, they have a lot of appendages. Not quite a thousand, as the name millipede suggests, however. Millipedes are also recyclers, feeding on decaying vegetable matter.

Everything that shows up in compost isn't feeding on dead material. Take that many-legged cousin of the millipede, the centipede. It has two pairs of legs on each segment and moves very fast. Its speed suggests it doesn't feed on decaying matter. In fact, it is a predator and makes it living feeding on other arthropods.

Black beetles can sometimes be seen running from the light when the compost is turned over. These beetles are known as carabid or ground beetles. They sometimes feed on decaying plant material, but some are predators, preferring to chow down on other arthropods.

This is also the case with the spiders that hang around the compost pile. The spiders, including the granddaddy longlegs, are happy to make a meal out of some of the creatures that live there.

The compost pile might be where gardeners consign their dead plants, but it is not a dead place. Arthropods by the millions are busy working day and night turning that plant tissue into compost. It's one of nature's dirty little jobs, but someone or some arthropod has got to do it.


Writer: Tom Turpin
Editor: Andrea McCann