Robberflies are keen-sighted insects that often fly around in small circles and snatch other insects out of the air, including bees. A caption under a beautiful photo of a robber fly by Runstedt B. Rovillos, says, “The short, strong proboscis is used to stab and inject victims with saliva containing neurotoxic and proteolytic enzymes which paralyze and digest the insides; the fly then sucks the liquefied meal through the proboscis.” Although the beaklike projection, or proboscis, they use to pierce insects could pierce even human skin, the critters don’t seem inclined to do so. One national park service website said you should not handle robberflies, that they can deliver a painful sting. Can and do are two different things, however, and I have never experienced any difficulty when handling robberflies. Others agree. The portion of their anatomy toward the rear that may look like a stinger but it is actually an ovipositor, or a depositor for their eggs. Thus I suggested my four-year old daughter put her finger out for one to fly to and land on. And she succeeded in attracting one. She was both happy and amazed. Robberflies don’t seem particularly nervous about making contact with humans.
One might be inclined to fear certain robberflies, as some varieties resemble bumblebees (Laphria Thoracica) and others even resemble wasps! The ones mimicking wasps are especially convincing. It may take an expert to distinguish that particular sort of robberfly, so perhaps it is wise not to touch what appears to be a wasp. It may be one! You don’t want to find out the hard way, don’t you agree? Consider this URL: http://www.brisbaneinsects.com/brisbane_robbers/WaspMimicRobberFly.htm
A robberfly has a total of five eyes. Two large complex eyes, with three simple eyes in between the complex ones. Robberflies have only a single pair of wings. In addition, they are hairy, many even appearing to have something resembling a moustache. The saliva of the robberfly has the ability to paralyze its victim and digest its insides. Although they don’t seem to mind approaching humans of their own volition, if you come across a robberfly and disturb his resting location, he will likely fly away in a somewhat awkward fashion, buzzing at you as if angry that he has been disturbed. You are most likely to find one in a warm, sunny, dry area with lots of weedy vegetation.
Galveston County, Texas Master Gardener (website) describes their life cycle thusly:
“An adult female lays whitish eggs in a mass that she then covers with a chalky protective covering. Eggs can be found on low plants, grasses or in crevices within soil, bark or wood.
Robber fly larvae are seldom seen… They resemble long, slender, light-colored worms…Living in the soil or decaying wood, this immature stage consumes organic matter, white grubs, beetle pupae, grasshopper egg masses and other soft-bodied organisms.
Robber flies… pupate in the soil. … the puparia migrate to the surface and emerge as adults.”*
The robberfly, though oftentimes considered ugly, is a very useful creature to the farmer, even eating things like grasshoppers, and becomes beautiful, once you get to know him. What a boon to the farmer, who loathes munching crop pests. If one is a beekeeper, though, this fuzzy insect may not be on their most wanted list. Yes, robberflies are even so bold as to snatch bees out of the air to eat! All things in all, though, the robberfly should be viewed as yet another example of a beautiful part of this earth, our home sweet home, and a boon to man. Why not spend a lovely summer’s day, one day, looking to spot our neighbor, the fuzzy robberfly?
* http://aggie-horticulture.tamu.edu/Galveston/beneficials/beneficial-27_robber_flies.htm
