Out My Backdoor: Meet the Tiger Bee Fly

Tiger Bee Fly
Tiger Bee Fly


By Terry W. Johnson

Although this is a hard-working pollinator, it draws our ire because female carpenter bees bore holes as long as 10 inches in bare wood on our homes, decks and other structures to lay their eggs. People try a number of techniques to thwart the bees, such as swatting them out of the air, spraying areas where they are boring with citrus sprays, trying to catch them in traps, plugging their holes with aluminum foil or steel wool, playing loud music near their nests, and treating their nest cavities with insecticides.

Unfortunately, many homeowners plagued with what they perceive is an arch nemesis do not realize they have a wild ally that works diligently throughout the warm months to control carpenter bees. Mother Nature's carpenter bee control agent is an insect known as the tiger bee fly (Xenox tigrinus).

Actually, this insect is not a bee at all; it is a true fly. However, the insect's name and menacing appearance would lead you to believe this is one critter you need to avoid. It is one of the largest flies you have probably ever seen. A tiger bee fly can measure anywhere from 0.75–1.75 inches long.

When viewed from the front its long proboscis gives the insect the appearance of a really big mosquito. Fortunately, the long, slender beak is not capable of drawing blood from man or beast. Its body is black and fuzzy suggesting it is a large bee. The fly's long tapered, swept back, clear wings are decorated with intricate black patterns. The markings along the trailing edge of the wing look somewhat like tiger stripes. Its huge eyes appear to be giant versions of housefly eyes. The insect's black abdomen is marked with two white spots.

When my wife spotted the first one in our yard she aptly described it as looking like a horse fly with stained glass wings.

Unfortunately, many tiger bee flies are killed by folks that mistake them for a stinging or biting insect. In truth, the tiger bee fly is harmless and highly beneficial.

Remarkably, in spite of tiger bee fly's ferocious appearance, it is a member of a suite of native pollinators that inhabit our backyards. The tiger bee fly uses its fearsome beak to sip nectar from flowers. Consequently, this bee fly can be seen hovering in front of blossoms adorning a number of flowering plants. (It is particularly fond of coneflowers and asters.) What makes it unique among its fellow native pollinators is a mating behavior that is straight out of a horror movie.

After mating, the female hunts carpenter bee nest sites. As such, they are often seen hovering near carpenter bee nests. Once the female tiger bee fly finds a nest containing carpenter bee eggs she lays her eggs alongside the eggs left by the bees.

The fly’s larvae are parasites. On hatching, they are extremely active and move about seeking carpenter bee larvae. The tiger bee fly larvae then attach themselves to newly hatched carpenter bee larvae and methodically drink them dry. When each tiger bee fly completes this vampire-like task all that is left of the carpenter bee is an empty hull. The carpenter bee is literally eaten alive.

Although this behavior seems gruesome, it ensures the carpenter bee larvae never live long enough to leave their nest. Who would have ever thought something like this might be going on within a carpenter bee nesting cavity?

Though you might have never seen a tiger bee fly, there is a chance one is living in your backyard. My wife and I have been living in our home for more than 40 years and had never seen one well enough to make a positive identification until a week ago. That’s when my wife spotted one basking in the sun on the side of the house. Since then I have spotted a pair mating.

Once people become familiar with the tiger bee fly, it often becomes one of their favorite insects. In fact, this popularity has prompted retailers to offer a number of tiger bee fly items such as shower curtains, sheets, comforters, mugs, clothing and even phone cases.

If you are looking for an ally to help control carpenter bee damage to your home and property, it makes sense to encourage tiger bee flies to take up residence in your backyard. One of the simplest ways to do this is to stock your yard with a variety of native nectar-bearing plants that provide blooms throughout as much of the year as possible. Also reduce or eliminate the use of insecticides.

I would like to believe the reason we are now seeing tiger bee flies and a wide variety of other different kinds of wildlife is because years ago we began implementing these recommendations.

I hope you will enhance your yard for wildlife. In the meantime, do not kill a large, scary looking insect that sports wings that look like stain glass windows. Perhaps it just might be a tiger bee fly, one that will help you win your war with carpenter bees.

Terry W. Johnson is a former Nongame program manager with the Wildlife Resources Division and executive director of The Environmental Resources Network, or TERN, friends group of the division’s Nongame Conservation Section. (Permission is required to reprint this column.) Learn more about TERN, see previous “Out My Backdoor” columns, read Terry’s Backyard Wildlife Connection blog and check out his latest book, “A Journey of Discovery: Monroe County Outdoors.”