Soldier beetles, often seen on flowers, are a common sight in summer gardens across much of North America. Also known as leatherwings, these insects are beneficial to gardens. They are pollinators and predators of several garden pests. One genus, Chauliognathus, prefers goldenrod and other members of the sunflower family.
Identifying Soldier Beetles
Soldier beetles (family Cantharidae) have soft wing covers and elongated bodies. There are around 470 different species worldwide, many of which are in the genus Chauliognathus. Like other beetles, soldier beetles have protective wing covers (elytra) that meet in a straight line over the abdomen. Those of soldier beetles are more leathery than shell-like. These are fairly flattened, elongated beetles with parallel sides.
The family gained the common name of soldier beetles because one of the first members of the family to be described was bright red, reminding the discoverer of the British red coats.
Many soldier beetles are colorful, marked with yellow, orange, or red, plus black or brown. They are soft-bodied with long legs and long, threadlike antennae. Some species look a lot like fireflies. Seen from above, however, the head is fairly visible (not covered by a platelike structure, as it is in fireflies). The adults are mostly diurnal (active during the day) are most numerous in spring, late summer, and fall, when they are abundant on flowers and foliage. As the adults feed, they also find opportunities to mate, and mating pairs are often seen on flower heads in late summer.
Life Cycle and Habitat
Each soldier beetle passes through four life stages during its life cycle and undergoes a complete metamorphosis. Like all larvae of beetles, the larvae of leatherwings look nothing like the adults. Soldier beetle larvae have a felt-like exoskeleton. They have almost a suede-like look to them and are black to gray in color. Their shape looks a bit like the Very Hungry Caterpillar because they have a rippled look to them due to each of their body segments being separated by an indentation.
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Overwintering takes place as dormant larvae under debris. In spring, the larvae become active, feeding on insects in the leaf litter and top layers of the soil. They pupate in early summer with the adults emerging in July. You’ll find the adult beetles in your garden from late summer through fall, during which time the female soldier beetles mate and then lay eggs into the soil. Females lay eggs in soil or leaf litter.
The larvae live on the ground beneath fallen leaves and in damp soil, as well as under mulch and other organic debris. The dark-colored, long, slender, worm-like larvae are covered with tiny dense bristles, giving a velvety appearance. They spend their time in the soil, where they are are predators of other insects, eating grasshopper eggs, small caterpillars and other soft-bodied insects. Also soldier beetle larvae tend to be terrestrial although they do climb plants sometimes.
Adults may be seen from July to September but are most abundant in August. They can be found in meadows, fields and in gardens.
Diet: Pollen, Nectar, and Pests
The adults are mostly diurnal (active during the day) are most numerous in spring, late summer, and fall, when they are abundant on flowers and foliage. As the adults feed, they also find opportunities to mate, and mating pairs are often seen on flower heads in late summer.
The adults of many soldier beetle species eat pollen and nectar from flowers, often pollinating the flowers in the process. Soldier beetles mainly feed on pollen and nectar. Because of their frequent contact with flowers, soldier beetles are important pollinators. They do not damage flowers or other plants and are harmless to people.
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Soldier beetles are considered beneficial for two reasons. First, the adults are important late-season pollinators. They move pollen from one flower to the next as they feed on the nectar. Secondly, the adults of some species eat prey such as aphids and other small insects. In addition, their predatory larvae feed on grasshopper eggs and the eggs of other insects, snails, slugs, newly hatched grasshoppers, and the caterpillars of various moths, among other pest insects. Soldier beetle larvae feed on the eggs and larvae of beetles, grasshoppers, moths and other insects.
The larvae are predators that suck the juices out of other insect larvae (such as maggots, earworms, and borers) and insect eggs. Larvae primarily eat eggs and larvae of beetles, moths, grasshoppers, and other insects. Adults are frequently found on a variety of flowers, where they feed on pollen and nectar in addition to insect prey such as aphids and mealybugs.
Species of Note
Goldenrod soldier beetles, Chauliognathus pensylvanicus, are also called Pennsylvania leatherwings. They are often abundant on goldenrod, roses and other flowers. They are our most common soldier beetles in North Carolina.
The Pennsylvania leatherwing is a half-inch-long, with tannish-orange wing covers that have an elongated black spot at the base of each of them. This margined leatherwing was spotted in my garden a few years ago. In the west, the brown leatherwing is more common. Other species include the margined solider beetle (C. marginatus), which is active earlier in the season and has more of a black streak than a black spot on their wing covers. The larvae of the margined soldier beetle is known to prey on corn earworms and corn borers, making it a friend of backyard gardeners and farmers alike. The Colorado plains soldier beetle (C.) This Colorado plains solider beetle is common in the central states.
Attracting Soldier Beetles to Your Garden
There are a few different things you can do to support a healthy population of soldier beetles in your garden. First, provide plenty of nectar sources. If you can keep the bees and butterflies happy, you can keep these predators happy, too. Late-blooming plants are key to the survival of leatherwing beetles since they are in bloom during breeding and egg laying. Goldenrod, asters, Joe Pye weed, Boltonia, Coreopsis, and other late-season perennials are excellent additions to the garden.
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In addition to providing a food source for the adults, you can help support larval soldier beetles by leaving the leaves in place throughout your flower beds. Instead of conducting a fall clean up, let the garden stand through the winter and keep the fallen leaves in place over the soil as a mulch year-round.
It is important to the life cycle of soldier beetles (and many other beneficial organisms) that they have undisturbed, mulched soil in which to pupate, so include permanent perennial plantings in gardens. A fragile and important community thrives at the interface between soil and organic matter.
You’ll also want to eliminate the use of synthetic chemical pesticides that could bring harm to these wonderful creatures. In addition to soldier beetles, there are thousands of other types of predatory beetles you should encourage in your garden, including ladybugs, fireflies, and rove beetles. Most of these feed on nectar and pollen from the same plant species as soldier beetles, so you’ll be benefiting lots of good beetles in addition to the leatherwings. Populations can be increased by gardening with good pollen and nectar plants.
Any habitat garden must include a water source; soldier beetles are particularly known to frequent moist habitats. Choose suitable flowers to bloom over a long season.
Defense Mechanisms and Mimicry
Both adult and larval soldier beetles of some species can exude foul defensive chemicals when they are threatened by other predators (or hapless humans who accidentally mishandle them!), but they do not bite people or animals. Their yellowish color is thought to signal that they don't taste good. Larvae, pupae, and adults all produce defensive secretions that discourage predators. Several insect species mimic the appearance of soldier beetles, taking advantage of the bad taste of soldier beetles to protect themselves.
Soldier beetles do not eat plants, mar foliage, or bring harm to the garden.