One of the things I enjoy about burning wood to keep my home warm is the added enjoyment I have watching who and what falls out as I put the wood in the wheelbarrow.
When I'm burning mixed conifer, wood-boring beetles seem to be the most abundant insects that fall out of the firewood, and among them the flat-headed borer—which becomes the metallic wood-boring beetle at maturity.
Wood-boring beetles usually get their start from fire. A fire in the forest is one of the most wonderful things that can happen to woodpeckers and the smaller competitors known as "gleaners," including nuthatches, chickadees and the like.
Adult wood-boring beetles go berserk when they sense smoke in the air. The urge to reproduce takes over and they go on a sex frenzy, following the smoke to its source.
As soon as—and at times even before—the trees cool off, introduction of the elements that will break down the wood begin the process of rotting. That makes the burned tree perfect substrate for food for juvenile beetles that hatch from eggs laid into and under the bark.
One of the most abundant and showy beetles to utilize our forests are the "jewel beetles," aka metallic wood-boring beetles; also called the Buprestidae. The elytra (hard covering on the beetle's back) is metallic green, red, orange, brown and other hues. In India, Thailand, Japan and other Asian countries, these beetles are used as living jewelry, highly prized by insect collectors.
There are over 15,000 species of jewel beetles known worldwide. One from Cooktown, Australia, Temognetha alternata, will knock your eye out. It's about 2 inches long and a living rainbow; the head is metallic green and the elytra has stripes of yellow, blue, red and azure.
This isn't something that just happened last week: there are fossilized jewelry beetles millions of years old that will also knock your eye out, and you don't have to go that far to find them.
The Green River Formation—covering a great deal of the Rocky Mountains—is rich in fossil insects millions of years in age. They're in the Eocene geologic formation, an enormous salad of fossil-laden rock that records the sedimentation in a group of intermountain lakes in three basins in present-day Colorado, Wyoming and Utah.
The sediments are deposited in very fine layers. Each pair of layers is called a varve, and represents one year; that's sediments representing a continuous fossil record of six million years. If fossil hunting is something you and your family enjoy, the Green River Formation fossil insects and fish will keep you so busy you'll even pass up your afternoon naps.
But back to the process. The larvae hatch and immediately begin chewing (ingesting) rotting wood which, with the chemicals they contain, make up the perfect food. It's those hundreds of beetle larvae growing inside the rotting wood that bring woodpeckers (and also shrews) to individual trees by the hundreds.
White-headed, black-backed woodpeckers and other wood blasters will be hammering away on the tree, digging out beetle larvae. Eventually, if the tree is of the correct texture, and there's a need for a home, the woodpeckers will excavate a nesting cavity which, when the original builder is through raising babies, it will be used—year-after-year—for nesting by nuthatches, chickadees, swallows, small owls and other smaller birds. In summer, migrating bats will also use the cavities for day roosts, and in winter adult mourning cloak and brush-footed butterflies will hibernate in them.
Wood-cutters occasionally miss seeing the nesting cavity and will cut a "wildlife tree" for firewood. That can sometimes be a disaster as the tree may have an active woodpecker nest with eggs and/or babies. But for sure, it will be loaded with beetle larvae that end up coming home with the woodcutter and stacked in the wood shed.
It's quite a sight to watch juncos, chickadees, nuthatches and small woodpeckers going in and out of the wood shed, searching for insect larvae on the outside of split pieces of firewood. If your wood shed is like mine, with a windbreak on the southwest side, the birds that hang out in your yard will have a safe and comfortable place to spend winter nights and plenty of insects and spiders to fill their bellies during the day.
Unfortunately, most of the larvae living in firewood never have the opportunity to make it to their adult lives. The big pine borers, for example, can take up to five years to make it from egg to larva to adult, and not many people's firewood supplies last that long.
Be that as it may, sometimes there are surprises that drop out of a piece of firewood. If that should happen to you and you don't know who you're looking at, please take a moment and place it into a container and give me a call, 541-480-3728, or just send me an email: email@example.com, and we'll have a good chinwag about your discovery.