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Soldier beetles

Also known as Leatherwings, Cantharidae

Beneficial or harmlessBeneficial
Soldier beetle (Rhagonycha) on goldenrod, dusted with pollen Photo: BruceDavidC · CC0

In short

Soldier beetles are soft-bodied, often orange-and-black beetles found on flowers, where many eat pollen and nectar and some also hunt aphids. Their velvety larvae live on the ground and prey on insect eggs, small insects and snails. They are harmless to plants and help keep soft-bodied pests in check.

How it looks

Adults are long and straight-sided, 1.5–28 mm, with soft, flexible, velvety wing covers; they are usually dark brown to black with orange, red or yellow. They sit openly on flowers in sunshine. Larvae are elongated, flattened on top, dark brown or yellowish and covered in fine hairs (hence "velvet worms"), reaching about 18 mm, and live in soil and leaf litter.

Signs

Orange-and-black beetles on flower heads, often in pairs; velvety dark larvae in leaf litter.

Life cycle

Egg, larva, pupa and adult; larvae can live one to three years in the soil and there are one or two generations a year.

What favours it

Flowering plants for adults and undisturbed ground or leaf litter for larvae.

Prevention

  • Keep flowering plants and some leaf litter or mulch.
  • Avoid broad-spectrum sprays, particularly on flowers.

Treatment

Start with the first step and move down only if the problem persists.

  1. No control needed.

Pros and cons

Pros

  • Some species (for example Cantharis) hunt aphids and other soft-bodied insects; adults are often seen on aphid-infested leaves.
  • Larvae eat eggs, larvae and pupae of other insects, plus snails.

Cons

  • Some species eat only pollen, nectar and honeydew and give no pest control.
  • Adults, larvae and pupae can release noxious defensive chemicals from abdominal glands if handled.

Look-alikes

Blister beetles
Some blister beetles (Meloidae) look similar; avoid handling orange-and-black beetles you cannot identify.
Fireflies
Some fireflies (Lampyridae), a related family, look similar.
Ground beetles
Ground beetles have hard, shiny wing covers and hide on the ground by day.

Where you find it

Outdoor flowering plants, especially umbellifers, daisies and goldenrod-type flower heads.

Sources

  1. Soldier beetles — UC IPM Natural Enemies Gallery
  2. Soldier beetle — Wikipedia

Written in our own words from these sources. Check a product label before using any treatment.