Biology and benefits of balloon and dagger flies in field crops

There are 208 species of balloon and dagger flies (Family: Empididae) in the UK, of which six are important for biocontrol.

Balloon and dagger flies are distinguished by a small, round head, large eyes and a hump-backed thorax. Shapes vary from slender to robust and they vary in size from tiny to large (1–12 mm).

The life cycle of these flies is poorly understood. There is probably one generation per year.

Larvae predate other insects in the soil or dead wood, or are aquatic.

Adults are typically predatory, with strong, piercing mouthparts. They predate aphids, psyllids, whiteflies, coccids, midges, thrips and mites.

Adults of some species feed on pollen and nectar.

Six species are considered important for biocontrol.

Balloon and dagger flies are very abundant in field boundaries and some crops.

Techniques to encourage balloon and dagger flies include:

• Providing field margins with a variety of flowering shrubs and herbaceous plants
• Avoiding cutting margins in summer
• Preventing pesticide drift into margins