Soldier Beetles Marching On

An adult goldenrod soldier beetle

Photo: Carol Shirk

Sometimes when an unrecognized insect wanders into the landscape, it is difficult to know if it is a friend or foe. Therefore, it is hard to know how to react. Soldier beetles in general, and the Goldenrod Soldier Beetle, (Chauliognathus pensylvanicus) specifically, are one of the good guys and should be encouraged to stick around.

Beetles, the order Coleoptera, are the single largest group of animals on the earth. They make up one-quarter of all animal species and one-third of all insects. In the United States and Canada alone, there are at least 30,000 species with well over ten times that worldwide. Not all of them are beneficial. It is easy to think of the bad guys: Colorado potato beetles (Leptinotarsa decemlineata), Japanese beetles (Popillia japonica), and Emerald ash borer (Agrilus planipennis), to name just a few.

However, there are a number of beetles that are beneficial. Lady beetles (more than 450 U.S. species in the family Coccinellidae) are well known as voracious predators of aphids and are well accepted as beneficial insects. 

Perhaps not as well know, fireflies (about 125 U.S. species in the Lampyridae family), are another beneficial insect.  The larva of these childhood favorites feed on slugs, snails, cutworm larva, and other soft-bodied pest larva, helping to keep detrimental insects at bay.

One largely unrecognized beneficial insect is the soldier beetle. There are more than 450 species of soldier beetles in the U.S. (family Cantharidae), but the most common one to the Midwest is the Goldenrod Soldier Beetle. They are nicknamed “leatherwings” because of their soft clothlike wing covers that resemble uniforms. They are roughly 5/8 inches long and dull orange.  They have two distinct black spots on the elytra, the hardened forewings which protect the delicate hindwings beneath. They do closely resemble fireflies, but have no light producing organs.

These beetles are often seen on goldenrod flowers, but they will also visit a wide variety of other plants, including anything yellow, milkweed, and many natives. Adults are common from July to September, but are most abundant in August. They feed on pollen and nectar of the flowers, but will also eat caterpillars and aphids and do no damage to the plants. They lack the correct body parts to sting or bite humans, so pose no danger.

Toward the end of the summer, the adults lay eggs in clusters in the soil. The rarely seen, mini-alligator looking larva hatch and live through the winter in this stage. During the spring they feed on grasshopper eggs, small caterpillars, maggots, and other soft bodies insects. They live in leaf litter, loose soil, and plant debris until it is time to pupate and emerge as adults in July to begin the life cycle over again.

These beneficial insects are a good reason to leave some parts of the landscape undisturbed so that they can complete their life cycle without being thrown into the garbage or landfill. Many beneficial insects overwinter in leaf litter and plant debris.  By leaving some areas undisturbed, it not only will benefit the soil and the ecosystem, but will help soldier beetles and a host of other beneficial insects. So, leave the leaves this year and help the beneficials.

Carol Shirk

Certified Master Gardener