|© Robin Brickman|
There are more than 2,500 species of ground beetles in the world so the chances are good that if you have a healthy yard one or two of these beetles will call your property home. Any reference to tiger beetles is dealing with one section of the ground beetle family, so we’ve combined them here since they are so similar. Found throughout North America, ground beetles can move very quickly. Unlike most insects ground beetles live a relatively long time; sometimes as long as four years and are fiercely voracious. Ground beetles are extremely valuable in keeping down pest insects.
Unlike most beneficials ground beetles like to eat slugs and snails.
Their menu includes:
• In The Lawn – army worms, chinch bugs, sod webworms, and white grubs
• In Trees – tent caterpillars, gypsy moth caterpillars, ants,
• In The Yard – slugs and snails, , eggs and larvae of the root maggot, cankerworms, house fly maggots, brown-tailed moths, satin moths, tussock moths and many other pests that have a soil-dwelling stage,. They also eat ants, flies, small beetles, bugs, caterpillars, spiders, aphids, and grasshoppers. A single larva can eat more than 50 caterpillars
• In The Vegetable Garden – aphids, asparagus beetle larvae and pupae, cutworms, cabbage worm larvae, cabbage root maggots, cabbage looper, green peach aphid, Colorado potato beetle eggs, larvae and pupae. They are on the ground around potatoes, cole crops, onions, tomatoes, eggplants, leafy greens and asparagus plants.
Description of Ground Beetles
Most adults are blue-black or brown. They are three quarters to one inch long, usually iridescent. The defined thorax (front) is narrower than the abdomen (rear of bug). Larval ground beetles are elongated and worm-like in appearance. Most larvae live in the soil or in leaf litter and other debris. Both the larval and adult ground beetles have powerful and prominent mandibles.
Where Can We Find Ground Beetles
Different species chose to work either during the day or during the night. Their colors have something to do with the choice. Night active species are black. Those brightly colored or metallic ground beetles are active during the day. They are generally found on the ground, but they also tunnel under objects and surface debris, and search for prey on leaves and flowers. The beetles hide under stones, logs, or in soil crevices or other cover (preferably moist or damp) during the day. They like to stay under stone walkways. Ground beetles will occupy lawns if grass is at least 2 ½ inches high at all times; 3 inches is better. Overwintering adult ground beetles emerge from pupal cell and lay eggs in the soil. The larvae feed on insects and slugs for two to four weeks then pupate in soil. The adults remain in soil for the winter, emerging in the spring.
A fun project for the kids is to try to trap and identify ground beetles. They are easily trapped by sinking a soup can into the soil flush with the soil surface. Then place four small stones in a square around the trap and place a piece of wood over the trap sitting on the stones. Since ground beetles tend to hide under logs, they will move to go under the piece of wood and fall into the can. It is okay to keep them for a day or two, but then they should be returned to the yard.
Warning - do not use insect light traps. Lights at night attract tiger beetles and the ground beetle. Don’t use bug zappers!
In The House
Ground beetles occasionally become minor pests by wandering into houses and buildings by mistake. They do not damage household structures or furniture and are harmless to people and pets.
Insecticides Kill Ground Beetles
Virtually all the insecticides recommended for use in the outdoor landscape will kill ground beetles as well as the target pest insect. So use any broad spectrum insecticide with great care, limiting the target area as much as possible. An area such as a lawn, when sprayed with such an insecticide, will be without the protection of ground beetles for three to four months.
Keeping Ground Beetles Around
Give them cover - Ground beetles love mulch of any kind. Stacks of firewood, brush piles, stacks of stones or bricks, or passive compost piles all offer cover and protection for ground beetles. Mow the lawn no shorter than 2 1/2 to 3 inches. Ground beetles will inhabit the area under any ground cover plants you have on the property.
Give them water - a shallow pie plate filled with gravel and kept filled with water is an excellent water source for ground beetles, spiders and other beneficial insects. Six to ten of these watering devices can be spread around the whole yard in ground covers, under shrubs, etc. Even if you never fill them with water, the rain will be retained and help these friends survive to eat more pest insects.