Biology and benefits of bugs as natural enemies of field pests

Bugs include true bugs (Heteroptera), aphids and whiteflies (Sternorrhyncha) and hoppers (Auchenorrhyncha). However, only Heteropteran species are natural enemies, and their contribution to pest control is unknown. Of the carnivorous families, only the flower and pirate bugs and damsel bugs, occasionally assassin bugs, occur on farmland.

There are 33 species of flower and pirate bugs (Family: Anthocoridae) in the UK. They are highly effective predators of field pests such as aphids

Bug identification

Flower and pirate bugs are difficult to identify to species level. They are small (2–6 mm) and generally flattened, oval or long, with a head that has a parallel-sided snout. The end antennal segment is coloured.

Bug life cycle

There are one to three generations per year and they overwinter as adults. Eggs are laid singly, just beneath the surface of their prey’s host plant. Each female typically lays 50 or more eggs and there are five nymphal stages. Adulthood is reached in about 50 days.

Benefits of flower and pirate bugs

Each predatory nymph consumes up to 240 aphids. Most adults are highly mobile and seek out their prey, making them effective predators. They are most found on trees and shrubs, where the larvae and adults feed on eggs and the immature and adult stages of immobile insects, such as thrips, aphids, mites and whiteflies. Some are specialised and feed on leaf-mining caterpillars.

Status

Unknown.

How to encourage flower and pirate bugs

They may benefit from floristically diverse field margins and non-crop habitats that contain alternative prey.

There are 12 species of damsel bugs (Family: Nabidae) in the UK. They are mobile and aggressive predators that feed on other insects, including field pests.

Bug identification

All species are brown, slender with long legs and a four–segmented beak. They are approximately 6–12 mm long.

Bug life cycle

Damsel bugs have one generation per year, although they are capable of producing hundreds of eggs laid in rows of 5–10 on plant stems. They have either four or five nymphal stages, overwintering as eggs or adults.

Benefits of damsel bugs

The adults are frequently flightless, but they are still mobile, aggressive predators that feed on a variety of insects. They are found on plants on the ground and in margins, shrubs and trees.

Status

Unknown.

How to encourage damsel bugs

They may benefit from floristically diverse field margins and non-crop habitats that contain alternative prey.

There are eight species of assassin bugs (Family: Reduviidae) in the UK. They predate flies, beetles and catapillars.

Bug identification

Assassin bugs can be large (4.5–18.0 mm) and have a short, curved rostrum.

Bug life cycle

They have one to two generations per year, although they sometimes take more than 1 year to reach maturity. Assassin bugs overwinter as eggs, larvae or adults.

Benefits of assassin bugs

Larvae and adults are predators of immature and adult stages of flies and beetles, as well as caterpillars. They inject lethal saliva for extra-oral digestion. They may also bite humans.

Status

Unknown.

How to encourage assassin bugs

They may benefit from floristically diverse field margins and non-crop habitats that contain alternative prey.