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. 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). 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.
Length: most from ¼ to just over ½ inch.
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.
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.
Some species are more common than others.
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.
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.
It is just fun to watch soldier beetles visit flowers in early fall.
The name “soldier beetle” apparently arose from the red-and-black patterns of many species, which resembled the bright red uniforms of soldiers (the beetles got their name before armies switched to camouflage uniforms). 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.
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.