Soldier Beetles

Nearly 500 species in North America north of Mexico
Family

Cantharidae (soldier beetles) in the order Coleoptera (beetles)

Description

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. 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. Seen from above, the head is fairly visible (not covered by a platelike structure, as it is in fireflies). Soldier beetles fly well.

The larvae are segmented, wormlike grubs with 3 pairs of legs. They are usually rather velvety, and whitish, tan, brown, or black.

Size

Length: most from ¼ to just over ½ inch.

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A yellow beetle with black spots sits on the end of a yellow flower petal
Soldier beetle in Springfield, MO
Habitat and conservation

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. One genus, Chauliognathus, prefers goldenrod and other members of the sunflower family. As the adults feed, they also find opportunities to mate, and mating pairs are often seen on flower heads in late summer. The larvae live in fallen leaves and other debris on the ground, under rocks and logs, under loose bark, and similar protected places.

Foods

The larvae are predators that suck the juices out of other insect larvae (such as maggots, earworms, and borers) and insect eggs. The adults of many soldier beetle species eat pollen and nectar from flowers, often pollinating the flowers in the process. Some species of soldier beetles prey on aphids and other insects.

image of Soldier Beetles Distribution Map
Distribution in Missouri

Statewide.

Status

Common. The name “soldier beetle” apparently arose from the red-and-black patterns of many species, which resembled the bright red uniforms of soldiers (before armies used camouflage). With a little imagination, the long wing covers, when open loosely at the end, look something like the tailcoats soldiers used to wear, too. The family name Cantharidae is from the Greek for “blistering fly,” and likely refers to the noxious chemicals these beetles often secrete in self-defense.

Life cycle

The life cycles of this family of beetles are similar to those of other beetles. Like other beetles, they all undergo a complete metamorphosis, which means they have four growth stages: egg, larva (grub), pupa, and adult. As the larvae grow, they shed their skin a number of times until they are large enough to pupate. The adult (beetle) stage is the life stage when they are sexually mature. This is basically the same process that butterflies, flies, and bees go through.

Human connections

Soldier beetles are beneficial to agriculture, since they pollinate plants, and some feed on aphids and other insects injurious to crops. The larvae, by feeding on eggs and other larvae, kill insects before they can reproduce. Plus, it is just fun to watch them visit flowers in early fall.

Ecosystem connections

As pollinators, soldier beetles help plants to reproduce. As predators, they help maintain the natural balance of insects in an ecosystem. Although many species use foul or pungent chemicals to ward off attackers, the larvae and eggs are vulnerable to many predators.