Identification and benefits of soldier beetles in field crops

There are 41 species of soldier beetles (Family: Cantharidae) in the UK, of which five are important for biocontrol.

Larvae are dark brown or grey, sometimes with a velvety appearance, highly segmented; almost worm-like.

Adults are narrow, elongated beetles (2–15 mm long), with soft bodies. Their name arose from the similarity of the red-coloured species to military uniforms. The wing cases are long, thin and covered with short dense hair, which gives them a dull, matt appearance. The adults can be brightly coloured, either yellow or red (as in red soldier beetles), or are dark brown or black (known as sailor beetles); sometimes with yellow-tipped wing cases.

Adults are good fliers and larvae can move from margins into fields.

One or two generations are produced each year. Adults feed predominantly on nectar, pollen and honeydew, but can be carnivorous, feeding on live and dead soft-bodied insects, such as caterpillars, spider mites and aphids. At mating time, they are often seen on the flower heads of umbellifers.

Larvae feed on vegetation but are rarely pests and, when larger, prey on fly larvae, caterpillars and earthworms.

Adults are carnivorous and feed on other flower visitors.

Five species are important for biocontrol; three are abundant on farmland.

Abundant in meadows and flower-rich field margins, they are frequently observed visiting umbellifer flowers, such as cow parsley.

Larvae prefer dense vegetation; cover crops in winter may encourage larvae into arable fields from field boundaries. Flower-rich habitats, especially those containing umbellifers, will attract adults.