Soldier beetles
Yes, it is helping you, or at worst doing no harm. Soldier beetles (leatherwings) are long, soft-winged beetles, usually orange, yellow or red marked with black, that gather on flowers in summer. The common goldenrod soldier beetle is about 1/2–5/8 in (13–16 mm) long and lives mainly on pollen and nectar; Wisconsin Extension says it may also eat small insects, though UC IPM says Chauliognathus adults eat only honeydew, nectar and pollen. Several other species eat aphids, and UC IPM notes they are very common on roses. The larvae live in leaf litter and soil, where they hunt insect eggs and larvae. Soldier beetles do not damage plants, and they neither bite nor sting. There is no need to control them.
At a glance
- Kind
- Wild — attracted, not bought
- Adult
- Most 1/4 to just over 1/2 in; family range 1.5–28 mm
- Larva
- Velvety, dark, up to 3/4 in (18 mm)
- Eats
- Adults: pollen, nectar, some aphids. Larvae: insect eggs and larvae
- Generations
- One a year; winters as a larva
- Seen
- Mostly spring to early summer in California; goldenrod species July–September, peak August
How it works
Soldier beetles are the family Cantharidae, with nearly 500 species in North America. The adults are flattened, parallel-sided beetles with soft, leathery wing covers, long legs and long, threadlike antennae. The one most people meet is the goldenrod soldier beetle, or Pennsylvania leatherwing (Chauliognathus pensylvanicus): orange, with a dark spot on each wing cover, on goldenrod, Queen Anne's lace, milkweed and other late-summer flowers from July to September. Its relative the margined soldier beetle (C. marginatus) flies in May and June.
The adults feed mostly on pollen and nectar. The sources differ on the goldenrod species: Wisconsin Extension says it may also eat small insects such as caterpillars, eggs and aphids, while UC IPM says Chauliognathus adults feed only on honeydew, nectar and pollen. Other species are predators of aphids and other soft-bodied insects, and some are very common on roses. The real hunters are the larvae. They are dark, velvety and worm-like, and live in leaf litter, plant debris and loose soil. There they eat insect eggs and larvae, including grasshopper eggs and small caterpillars. Most gardeners never see them.
The adults protect themselves with defensive chemicals, and their bright colour is thought to warn predators that they taste bad. In Minnesota they spend the winter as larvae, pupate in early summer and emerge from late July, so there is one generation a year. Mating pairs are a common sight on flower heads in late summer.
What it is confused with
Soldier beetles are sprayed because they look like two other soft-winged beetles, one of them a real pest. Look at the head and the shape of the body.
- PestBlister beetles — A blister beetle's head is broad and joined by a narrow neck, the section behind it is narrower than the head, and the wing covers curve round the body. Soldier beetles are flatter and parallel-sided. Blister beetles chew leaves and flowers in clusters, and their body fluid raises blisters on skin, so do not handle them.
- Also goodFireflies — Close relatives that also have soft wing covers. From above, a firefly's head is hidden under a plate-like shield; a soldier beetle's head is clearly visible. Soldier beetles have no light organ.
- Also goodWasps and bees — Soldier beetles fly readily and move fast between flowers, so they can pass for wasps. Look for wing covers meeting in a straight line down the back; wasps and bees have no wing covers, only clear wings.
How to keep it around
Adults feed at flowers, and the larvae need undisturbed ground. Extension sources suggest:
- Late-summer flowers: goldenrod, yellow composites, Queen Anne's lace, milkweed and rattlesnake master (Eryngium yuccifolium)
- Yellow flowers in general, which Minnesota Extension says attract the adults most
- Leaf litter and plant debris left under shrubs and in borders, where the larvae live and hunt
- No spraying for them: they are harmless, and Minnesota Extension says to ignore them and they will go away on their own
When to choose something else
Soldier beetles are a welcome bonus, but they turn up for a few weeks and the goldenrod species eats mostly pollen. Look elsewhere when:
- Aphids are building on roses in spring — UC IPM advises knocking them off with a strong spray of water early in the day and keeping ants off the canes; see rose aphid
- Aphid colonies need predators whose larvae feed inside them — UC IPM finds hoverfly larvae within aphid colonies, and lists lady beetles and their larvae among the natural enemies of rose aphid
- Long beetles are chewing leaves in clusters on tomatoes or potatoes — those are blister beetles; wear gloves
Soldier beetles by target
What it eats and when it turns up differ by pest. Each page below is the picture for one target.