Creature Feature
Ground Beetles
by Gary Winans
In the Fall/Winter 1995 issue of The Riparian Zone, I wrote about midge flies and how they have adapted to the loss of wetlands habitat in our neighborhoods. This time I want to tell you about another cool insect that has also survived urbanization, the European ground beetle Ground Beetle sketch
Related to whirligig and tiger beetles, the European ground beetle is among
the 1000 species of beetles found in the Seattle area. What's cool about these
critters is that they are easy to find and fun to observe. They may be the most
common beetle around here—it sure is in my neighborhood—and one of the largest:
adults are about 3/4" long.
The adult European ground beetle is shiny black, tinged with hues of violet
or greenish bronze. If you look closely, you'll see they have three rows of pits
along each side of their back.
Juvenile or larval ground beetles look entirely different and look more like
worms. The larvae live in tunnels in loose soil. They are predators and eat
insects and other small critters that wander by their tunnels. Eventually, the
larvae will seal off their tunnel and undergo a quiet or pupal stage during
which time they "morph" or change into adult beetles.
Adult beetles hide during the day under logs, rocks, and in crevices. By night, they roam your backyard looking for insects, cutworms, and grubs to prey upon. I've discovered many ground beetles in my backyard while tilling soil. And I've seen them under fallen logs along Longfellow Creek and at Camp Long. In the summer, armed only with flashlights, we take family slug hunts in the garden. Not infrequently we have discovered a ground beetle moving through the lettuce patch with one of those 1/2" long slugs trapped in its mandibles.
According to one source, ground beetles and their relatives have been around for tens of millions of years. But like other beneficial insects that have survived through the ages, they are very susceptible to pesticides used around home and garden. Using chemicals sparingly or not at all will help protect this natural predator in your backyard. I still have lots of unanswered questions about ground beetles. For example, how far does a beetle range every night while hunting, and where does it hide and sleep by day in my garden? So when I see this cool critter scuttling across my path, its shell glistening in my flashlight beam, I bend down and, for as long as I can, watch this backyard predator of grubs, cutworms, and slugs.
For more information about ground beetles and their relatives, get a copy of the Peterson's Field Guide to Beetles and the WSU Cooperative Bulletin EB1447. Both have nice color photographs.