robber fly

any of numerous swift-flying, often large, dipterous insects of the family Asilidae that are predaceous on other insects.

[1870-75]

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or assassin fly

Any of about 4,000 species of predatory dipterans in the family Asilidae, found worldwide.

Robber flies are the largest of all dipterans; some species are 3 in. (8 cm) long. Most have a dull-coloured, stout body resembling that of a bumblebee and a moustache of bristles between the large-faceted eyes. They use their long legs to capture insects in flight and hold them while eating; a fluid injected into the victim breaks down muscle tissue. A few species are serious pests of apiaries.

Robber fly (Asilidae)

William E. Ferguson

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▪ insect

also called  assassin fly 

  any of about 6,750 species of predatory insects, worldwide in distribution, in the fly order, Diptera. Robber flies range in length to almost 8 cm (3 inches), making them the largest of all flies. Most are dull in colour, and their stout, often hairy, bodies resemble those of bumble bees. Between the large-faceted eyes is a moustache of bristles. The long legs are adapted to capture prey in flight and to hold it while eating.

      The robber fly is a predator of almost all flying insects. It injects a fluid into its victims that breaks down the muscle tissue. A few species of the genus Promachus are serious pests of apiaries because they feed on bees. Each species has a characteristic habitat—e.g., tree trunk, foliage, grass, low plant, dead twig, gravel, or beach sand.

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