COMMON NAME

Robber fly

Order

Suborder

Family

Genus

Species

Alias

Diptera

Asilidae

Assassin fly

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Description

Their typical shape is a long tapering body although there are some species that are fatter and rounder. Some species mimic wasps or bees and will be more colourful but mostly they are grey, brown or black. Generally the thorax is short and squat with bristles over it. They have strong spiny legs with a pair of claws on each one for catching other, sometimes quite large, insects. The larvae live in the soil and are a pale yellow, quite small and grub-like.

Adult size: 1.7mm - 75mm

Out and about

Robber flies are active during the hottest part of the day over spring through to autumn when their prey is most abundant. They like dry, warm climates and open space; they do not do well in forested areas. . They are found all over the world and in various habitats apart from Antarctica, but the majority of species live in tropical or subtropical regions as well as arid and semi-arid climates. In Australia they occur throughout most of the continent but are most concentrated on the east coast with many species native to the country.

Reproduction and Life cycle

The female will lay her eggs in the soil, beneath bark or in rotting wood, often in clusters and then produce a protective coating over them. The larvae will remain in this environment feeding on any eggs, larvae or other insects they come across. They will pupate in the soil, emerging as adults in the spring. The duration of the life cycle depends on the species and environmental conditions ranging from one to three years.

To deter

To control

Plants to repel

Plants to attract

Caraway / Marigolds / Calendula / Sunflowers

Predators

Why they are Beneficial

Robber flies wait and ambush their prey, catching them mid-flight. They attack wasps, bees, dragonflies, grasshoppers, other flies, ants, moths, butterflies, spiders; in fact just about anything. They inject a poison into their prey which enables them to digest the insides of the insect with only the exoskeleton left behind when they have finished. The larvae are also predatory, feeding on small insects on the ground.

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