Can You Identify These Pollinators? Part 1: Bees, Wasps, Flies

Written by Mary Free, Certified Master Garden

Bees

As bees feed on the nectar of flowers (particularly those that are bright white, yellow or blue or with contrasting ultraviolet patterns), their electrostatically charged and branched body hairs attract and trap pollen grains. They carry the grains from flower to flower, which makes them very effective pollinators. According to the U.S. Forest Service, “bees pollinate approximately 75 percent of the fruits, nuts, and vegetables grown in this country.” [Unfortunately, bee populations have suffered dramatic declines over the past 50 years. Read How to Celebrate National Pollinator Week: Go Native! to find out how you can help.]

European honey bee (Apis mellifera) on blue wood aster (Symphyotrichum cordifolium) © Mary Free

European honey bee (Apis mellifera) on blue wood aster (Symphyotrichum cordifolium) © Mary Free

Among the estimated 485 different bee species in Virginia (Adamson, 2009*), you undoubtedly recognize the most well known—the European honey bee (Apis mellifera)—but do you know that its ancestors first arrived in the “New World” in 1622? They were brought to the Colony of Virginia not for their pollination services but rather for their wax- and food-making abilities. Today their honey is still valued, but more important, these industrious insects pollinate U.S. crops estimated to be worth more than $14.6 billion (Morse and Calderone, 2000).

Black and gold bumble bee on MonardaC

Black and gold bumble bee (Bombus auricomus) on Monarda © Mary Free

You also probably recognize this hairy insect as a bumble bee. Among the 21 species of Eastern bumble bees−18 of which are found in Virginia—this large, 3/4 to 1-inch long black and gold bumble bee (Bombus auricomus) is considered uncommon. Photographed six years ago at Green Spring Gardens Park, it is feeding on one of its favorite flowers, Monarda.

Bumble bees are important pollinators of tomatoes, blueberries, cranberries and melons. Like honey bees, females use baskets (corbiculae) located on their hind legs to carry pollen. [To see pictures of different pollen-carrying apparatus, read Bee-havior: Gathering and Transporting Pollen.] Instead of hives, though, they live in small colonies in vacant rodent nests, tunnels and hedges.

Sweat bee on Coreopsis verticillata

Sweat bee (Family Halictidae, probably Tribe Augochlorini) on thread-leaf coreopsis (Coreopsis verticillata) © Mary Free

What would a bee named for its attraction to the salts in human perspiration be called other than a sweat bee? If this tiny bee—1/8 to 3/8-inches long—lands on you, resist the urge to swat it. Regardless, don’t sweat being bit or stung (unless you have a bee allergy). It will feel like a pin prick, or, according to the Schmidt Pain Index, “as if a tiny spark has singed a single hair on your arm.”  [Learn more about entomologist Justin Schmidt and his insect pain index.]

Virginia is home to 45 species of these (mostly) ground-nesters that range in color from dazzling metallics to a dull brown/black. They are generalist pollinators, able to extract and digest the pollen of many different types of flowers. Like bumble bees, sweat bees practice “buzz pollination” or sonication. By rapidly moving its flight muscles, a sweat bee can cause sonic vibrations that release the pollen of certain plants, like tomato.  Unlike honey or bumble bees, though, females carry pollen on dense, hind leg hairs called scopa.

Leafcutter bee on Rudbeckia

Leafcutter bee (Genus Megachile) on Rudbeckia © Mary Free

What would a bee named for cutting circles in the leaves of your smooth-leaved plants (like roses, azaleas, lilacs, or asters) be called other than a leafcutter bee? This nonaggressive and solitary bee removes leaf fragments in less than 10 seconds and carries them back to the nest to form into cells for its eggs. A valued wildflower pollinator numbering 36 species in Virginia, the females use scopa located on the underside of their abdomen instead of their hind legs to carry pollen.

Wasps

When you hear the word wasp, you probably cringe and think of yellow jackets chasing you away from your picnic food (or attacking en masse if you disturb their nest). These ornery—yes waspish—creatures become more aggressive in the fall as they scavenge for human food when their local food supply dwindles just as their population peaks. It is right to be wary of them. Schmidt’s description of their sting tells you to “imagine W. C. Fields extinguishing a cigar on your tongue.”

Yellow jackets, however, give wasps a bad name. Most wasps are solitary, nonaggressive, beneficial insects, doing double duty as both pollinator and predator. They are more interested in stinging their insect pest prey than in stinging humans.

Blue-winged wasp (Scolia dubia) on hyssop-leaf thoroughwort (Eupatorium hyssopifolium) © Mary Free

Blue-winged wasp (Scolia dubia) on hyssop-leaf thoroughwort (Eupatorium hyssopifolium) © Mary Free

For instance, as you gaze across your lawn in mid-to-late August, you may observe Scolia dubia flying low in a figure-8 pattern searching for the grubs of destructive green June and Japanese beetles. When a female senses a grub, she burrows into the ground and stings and paralyzes it. Grubs, on which she lays an egg, will feed her developing larva. (Don’t worry; scolid wasps rarely sting people unless you step on or handle them. Instead, you should be more concerned with the damage a significant grub population can inflict on your lawn.) You can find these wasps feeding on the nectar of flowers like Boltonia asteroides, Eupatorium hyssopifolium, and Solidago canadensis.

Scolia dubia wings gleam an iridescent blue, depending on the lighting, which accounts for its common name, blue-winged wasp. It also is called a digger wasp since it digs into the soil to find grubs. However, as is true with some common names, it shares the latter name with another wasp species in the genus Sphex.

Flies

Syrphid fly, probably Eupeodes, on New England aster ‘Purple Dome’ (Symphyotrichum novae-angliae) © Mary Free

Syrphid fly, probably Eupeodes, on New England aster ‘Purple Dome’ (Symphyotrichum novae-angliae) © Mary Free

Is it a bee? Is it a wasp? No, it is a syrphid fly. Flies have only two wings, stubby antennae and big compound eyes. Syrphid flies do not sting but since they look like bees or wasps, predators avoid them. Also called hover flies, they can hover and fly backwards, unlike most insects. Adults frequent flowers earning them another name: flower flies.

Not only are some syrphid flies better pollinators than native bees (for crops like apples and mangoes), but some, in their larval form, rival ladybugs in consuming aphids. The University of California (Publication 8285) informs us that “on California’s Central Coast it is primarily syrphid larvae that enable organic lettuce growers to produce harvestable crops (Smith and Chaney 2007).” So the next time you eat a salad, think of these insects, and by whichever name you use, celebrate these important pollinators/predators and call them friends!

*The numbers for various bee species found in Virginia are from an April 18, 2009 presentation, Non-Apis Bees Important for Crop Pollination in Virginia and Other States, by Nancy Adamson.

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