Robber flies, known in Thai as malaeng wan hua boob, have stout, spiny legs, a dense bristle of hairs on the face, and three simple eyes in a distinctive dent between two larger compound eyes, and short antennae.

They posses a bristle-like structure and a short, strong proboscis, used to stab victims, which they then inject with saliva containing neurotoxic and proteolytic enzymes, that paralyze and digest the internal organs, allowing the robber fly to suck up the liquefied insides.