Beneficials on farmland: identification and management guidelines (HGCA Summer 2008)

Beetles (Coleoptera)

Over 4,000 beetle species are found in Britain.

Beetles are rarely confused with any other insect group. There are typically two pairs of wings. The hard, or leathery, front pair meet along the middle of the back, forming ‘wing-cases’, to protect the membranous hind wings which are usually folded away out of sight. All beetles have biting mouthparts.

Some beetles and their larvae, and weevils (distinguished by a prominent snout), may be pests, eg leaf beetles (Chrysomelidae), but can also be important as food, particularly for game birds.

The diet of beetles includes other insects, slugs, weed seeds, fungi and detritus.

Most beetles can, and do, fly. However, they spend most of their time on the ground or in low vegetation.

Ground beetles (Carabidae)

  • About 350 British species
  • Variable size (2–25mm)
  • Good runners and may climb
  • Frequently black or brown, often with metallic sheens
  • Many are nocturnal
  • Overwinter as adults under tussocky grasses or as larvae underground in fields
  • Many adults and larvae are carnivorous
  • Many feed on insects, slugs and seeds

May be confused with weevils and soldier beetles.



Ground beetle (Anchomenus dorsalis)


Pterostichus spp – present in fields all year round. Feed on slugs and other invertebrates. Overwinter as larvae in fields and so favoured by minimum tillage. Demetrias atricapillus – overwinter as adults in field margins. Fly into crops during spring to forage. Feed on cereal aphids and other prey on foliage. Partially control low aphid populations. Favoured by beetle banks and grass margins.

Rove beetles (Staphylinidae)

  • About 1,000 species
  • Variable size (1–25mm)
  • Good fliers and climbers
  • Short wing cases, unlike ground beetles
  • Overwinter as adults under tussocky grasses or as larvae underground
  • Predatory, or fungal-feeding
  • Favoured by beetle banks


Rove beetle (Anotylus mutator)
Adult rove beetles climb cereal stems at night to feed on aphids.

Ladybirds (Coccinellidae)

  • 40-50 species in Britain
  • Variable size (1–10mm)
  • Brightly coloured
  • Usually red or yellow with black markings
  • Virtually all predatory
  • Adults and larvae feed on pests, particularly aphids

Larvae may be confused with leaf beetle larvae


Larva


Eggs

Adult ladybirds lay eggs among aphids on leaves. Larvae and adults are voracious feeders and can reduce aphid populations.



7-spot ladybird (Coccinella septempunctata)

Pupa

Soldier beetles (Cantharidae)

  • Narrow elongated beetles with soft bodies
  • Variable size (1–10mm)
  • Dull, matt appearance due to short hair on wing cases
  • Frequently visit flowers, particularly cow parsley
  • Carnivorous, feed on other flower visitors

May be confused with carabids

Adult soldier beetles hibernate off the crop.



Soldier beetle (Cantharis fusca)

Leaf beetles (Chrysomelidae) – Non-beneficial species

  • Approximately 250 British species
  • Variable size (1.5–10mm)
  • Can be brightly coloured with metallic sheen and chunky legs
  • Both adults and larvae important as bird food
  • Some species are pests, eg flea beetle (Halticini spp)


Cereal leaf beetle (Melanopa spp)
Adults may be confused with weevils or carabids; larvae with ladybird larvae

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