IT'S THE APHID-EATING LADYBUG THAT comes to mind when we think of a beneficial insect. Colorful, cute and almost cuddly, gardeners cherish this industrious little beetle. The subject of neckties, aprons, sun hats, T-shirts and statuary, the ladybug is treated like a god in the garden world. But other good beetles, like the soldier beetle and the common ground beetle, inhabit local yards. Since they lack the pulchritude of the lady beetle, many ignorant gardeners fear their appearance and often mistake them for pests. These scrappy beetles consume a wide array of detrimental pests and deserve to be recognized.
To discover soldier beetles (also called downy leatherwings) scampering about the garden is like finding gold. These valuable beneficials greedily consume aphids, spider mites, small caterpillars, grasshopper eggs and cucumber beetles. Soldier beetles are a curious looking lot. A typical beetle on the West Coast has a reddish orange head, black eyes, long wiggling antennae and a half-inch long, narrow body covered with velvety black elytra. Elytra are the thick wings of a beetle that cover the delicate, functional wings lying next to the beetle's body. Wingless larvae, also about a half-inch long, feed on insects lurking in the soil and under bark and thick mulch.
Soldier beetles may look wiggly and creepy, but they will not harm you. They are just as cuddly as ladybugs. Adults are attracted to flowers that produce nectar and pollen like milkweed, hydrangea, goldenrod and nectar-laden roadside weeds. They like to deposit eggs in rotting bark and plant material. Compost piles and areas thick with decomposing mulch are ideal habitat for soldier beetle larvae. The larvae hatch in mid-May, just when aphids begin to congregate on the buds of roses.
You could say the common ground beetle and its cousin, the fiery searcher, are the shy bullies of the garden. Feeding only at night, they run for cover if dislodged from the daytime hiding places. You may have come across them when pulling tall weeds, moving old pieces firewood or dislodging garden debris. Their heavily armored bodies move quickly, albeit clumsily, across lumpy ground.
Ground beetles are almost black and shiny. About an inch long, they possess intimidating pincer jaws that look menacing, leading the unsuspecting gardener to want to squash them. Fiery searchers, a ground beetle also, have thick, metallic green elytra. When frightened, these beetles will point their rumps upward and give off unwelcome secretions, which can put off the unaware gardener.
Despite their frightfulness, ground beetles are a treasure to have in the garden. They ferociously consume caterpillars, cutworms, root maggots, slugs and snails. Hungry larvae are narrow brownish-black, about 3/4-inch long. Their fearsome pincers grasp maggots and cutworms and other soft-bodied soil insects.
While good sanitation is always desirable in a garden, it can be overdone when creating habitat for beneficial insects like the soldier beetles and ground beetles. Allowing patches of wild grasses, weeds and native pollen-producing flowers around the fringes of the garden creates a meadow effect. This attracts soldier beetles. Old wood piles, thick grassy areas and unturned compost piles are ideal habitat for ground beetles. Larvae like to hide out in thick lawn turf.