What’s more fun than a “barrel of monkeys”? How about a log filled with squiggly bugs and slimy slugs?
Fallen trees and dead branches in your garden make great places for kids to explore a new world filled with many-legged mini-beasts and occasional larger ones. Turn over a log and what do you see? Can you hear the mini-beasts at work? What does the log feel like to the touch? Open your eyes and ears and get ready to explore the living world in a dead tree.
Some of the first bugs to move into fallen trees are wood-boring insects. Female beetles bore little tunnels into the wood and lay their eggs. Later, the larvae burrow outward with their strong jaws. Although the beetles are chewing through the wood, it is actually the bacteria and fungi on the tunnel walls that provide nutritious food for the beetles.
How do the fungi and bacteria get there? The beetles “plant” it in their tunnels in the form of their droppings. The combination of wood-boring beetles, fungi, and bacteria helps the wood to decay. Do you see any tunnels or openings from wood-boring beetles? Other tunneling dynamos are carpenter ants and termites. They carve extensive mazes of tunnels far into the wood. Knock on the wood and listen with your ear up close. Do you hear a rustling sound? Carpenter ants make this sound with their mandibles (jaws). If you hear a “ticking” sound, then you may have discovered termites.
The vast tunnels of beetles and ants become “highways” into the log for moisture, fungus, bacteria, and other small creatures. With such enticing pickings, is it any wonder that a fallen tree becomes a banquet table for other animals? Hungry centipedes prowl the dark recesses of the log, looking for worms, slugs, spiders, and even other centipedes to dine on.
The many-legged millipede, which is related to the centipede, isn’t a predator, but rather feeds on rotting wood and decaying leaves. The millipede, if it is not careful, can easily become dinner for a shrew – a furry, four-legged creature that is our smallest mammal.
From above, small female wasps, called ichneumons, land on the log. Using very long ovipositors, (egg-laying organs), they can lay their eggs into beetle larvae far below. The eggs hatch into wasp larvae that eat their hosts, the beetle larvae. Woodpeckers also visit fallen logs where the wood-boring larvae provide a year-round source of food. After drilling into the wood with his strong beak, the woodpecker slurps up the juicy larvae with his long tongue. What a yummy meal!
A dead log is more than just “litter” on the forest floor. Approximately one-fifth of woodland creatures depend upon dead trees for their homes. Dead trees also provide moist places for ferns, mosses, fungi, and tree seedlings to grow. They harbor insects, spiders, and other little animals that either eat the log or are eaten by other animals. The health of the forest itself is dependent upon the life in decaying logs.
Through decomposition, nutrients in the log are slowly returned to the soil for new plants to grow. Thus, a dead log is part of the cycle of life. You have probably seen a nurse log on your woodland walks and thought it was just a long mound of soil. A nurse log is a fallen tree that in time becomes completely enveloped with new vegetation – mosses, ferns, fungi, and sprouting seedlings. Keep an eye out for these shapes now that you know how they formed.
Barbara Bray is president of the Oakland (MI) Chapter.
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Updated: Oct 20, 2006.