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If you have ever watched a rather large wasp-like insect as it quickly flies out to catch another insect in mid air, you have probably seen a robberfly. Amazingly, most people do no realize that this type of behavior is in no way related to the way a wasp hunts for food. Robberflies are often mistaken for various different species of bees or wasp but are the only insect of the three that hunt in this manner. Insect lovers who desire to observe the robberfly should find a wooded area that borders a meadow in the early part of summer. Sit at the edge of the woods and watch for a rather large insect with long legs to zoom out of the trees to catch another flying insect. If you can follow the path of this insect back to its perch you will notice that this behavior is repeated over and over until the robberfly has eaten its fill or made enough passes at insects to ensure that none of its choice are available. When it is possible to get a closer look at the robberfly you will notice that the body has tiny hair like appendages that give this insect a rather bristly appearance around the head area. You might also notice that as any possible prey comes close, the eyes of this insect follow its progress intently. Interestingly, the robberfly does not snatch every insect it flies out at. In some cases this insect is merely investigating to see if the possible food source is acceptable. It prefers bright sunny areas to hunt in, only regressing into the shadows to eat.
One of the largest flies in the Asilidae family this busy insect has many interesting habits. Even though it may appear that the robberfly is chasing its prey, this is never the case. Since its vision is considered excellent the robberfly simply flies out to check out anything that moves. Occasionally these insects have been observed even flying out to check out a leaf falling from the tree they were perched on. Interestingly, this insect is capable of gauging the distance and speed of the object moving out in front of it. As it flies out it intercepts the object and if it is acceptable prey the robberfly stab it in mid air with its piercing mouth appendage. It will then return to its perch and busily eat its catch. This process begins with the robberfly injecting a fluid into its prey that liquefies the internal parts of the insect so it is easily sucked out. With close to 4,000 species of robberflies found throughout the world this highly predatory insect preys on most flying insects included some species of bees and wasp. In many areas the robberfly is considered an acceptable insect and commonly called the assassin fly since it often eats various different plant pest. But in some locations certain species of the robberfly are considered a pest, preying on beneficial bees.
Robberflies mate shortly after emerging during the early summer weeks. The mating rituals of these insects include aerial displays and buzzing sounds that are different from their normal buzz. Once the female has been fertilized she will deposit her eggs in the soil. During the winter months the eggs will hatch with the larvae remaining under the soil. These minute worms begin moving about under the soil and feeding just as spring arrives. Pupation occurs while the larvae are still in their protective soil burrows but shortly afterward they will move to the surface and emerge as adults.
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