Robber flies

Definition

A family of predatory true flies (Diptera: Asilidae), also called assassin flies, characterized by a stout, bristly body, large compound eyes, strong raptorial legs, and a short, rigid proboscis used to pierce prey and inject paralyzing saliva. Adults are active aerial predators that typically perch in open habitats to ambush flying insects, seizing them in flight and carrying them to a perch to feed. Larvae are generally found in soil or decaying organic matter, where they prey on other invertebrates or act as scavengers.

Etymology

From the predatory habit of seizing prey in flight, likened to robbery; 'assassin flies' emphasizes their lethal ambush tactics

Example

The large, bee-mimicking robber fly Promachus bastardii waits on bare ground in open fields, darting upward to capture honey bees, wasps, and other flying insects, which it immobilizes with neurotoxic saliva before sucking out the liquefied tissues.

Synonyms

• assassin flies
• Asilidae

Related Terms

• Diptera
• raptorial legs
• Proboscis
• ambush predator
• aerial predation
• mimicry
• Entomophagy
• predatory behavior

Usage Notes

Strictly refers to family Asilidae, not to be confused with other predatory flies such as dance flies (Empididae) or stiletto flies (Therevidae). The vernacular 'assassin flies' is increasingly preferred in technical literature to avoid confusion with assassin bugs (Hemiptera: Reduviidae). Species range from small, slender forms to robust, bumblebee-sized predators; all share the characteristic concave mystax (bristles on the face) and predatory lifestyle.