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U.S. Forest Service

Fly Pollination

The two-winged insects (flies, gnats, mosquitos) is a very large group. Many of them specifically visit flowers, such as the Syrphid flies or flower flies. They are not as hairy as bees and as efficient in carrying pollen, but some are good pollinators.

Fly Flowers

The flowers that are pollinated by flies are typically:

  • Pale and dull to dark brown or purple
  • Sometimes flecked with translucent patches
  • Putrid order, like rotting meat , carrion, dung, humus, sap and blood
  • Nectar guides not present
  • Produce pollen
  • Flowers are funnel like or complex traps

green bottle fly on a pink flower. Blow fly or green bottle fly. Photo by Beatriz Moisset, 2002-2004.

Tachinid fly on catnip flower. Tachinid fly on catnip. Photo by Beatriz Moisset 2002-2004.

Mosquito on a white flower. Did you know that mosquitoes are pollinators? Mosquitoes are known pollinators of bog orchids, Habenaria obtusata. Photo by Beatriz Moisset.

Hairy-legged fly on a yellow flower. Hairy-legged fly (Trichopoda pennipes). Photo by Beatriz Moisset.

Bee Mimics

Some flies, such as syrphids, masquerade as bees and wasps. However, the pollinating flies can be distinguished with a sharp eye. The flies have only one pair of wings while bees and wasps have two pairs of wings. Comical, robust and extremely hairy are the bee flies (bombylids), some with tongues as long as their bodies!

syrphid fly on a yellow flower. The syrphid fly is a bee mimic. Photo by Beatriz Moisset 2002-2004.

tachnid fly on a yellow flower. The tachnid fly is similar in general appearance to bees or wasps. Photo by Beatriz Moisset 2002-2004.

A bee fly on a yellow flower. A bee fly, a good bee mimic. It lays eggs near bee nests and its larvae feed on bee larvae. Photo by Beatriz Moisset.

Putrid Odor

Putrid smelling blossoms are an adaptation to attract certain fly pollinators. Even male mosquitoes (relatives of flies) get in on the act since they pollinate certain orchids. Long-tongued flies (e.g., syrphids, bombylids) feed on same flower types that bees do. Short-tongued flies feed on flowers that imitate the main source of food for flies. Flies may be trapped for a time in the flower while they feed; e.g. Stapelia, Dutchman’s pipe.

Pawpaw flower. Jack-in-the-pulpit flowers have a fungus-like smell that attracts many tiny insects, particularly fungus gnats. Photo by Steve Baskauf.

Pawpaw flower. The meat-colored petals and fetid aroma of pawpaw (Asimina triloba) attract flies and beetles. Photo by Steve Baskauf.

A bee fly on a yellow flower. Skunk cabbage's strong smell and dark color attract carrion flies that lay their eggs thinking that it is rotting flesh. Photo by Beatriz Moisset.

Rotten Meat?

Red Trillium is a beautiful flower with a less than beautiful odor. Many wildflower enthusiasts claim that this flowering beauty smell like rotting flesh. Although humans may not find this smell attractive, flies are drawn to these brilliant red blooms.

The deep red color and putrid odor resemble decaying meat and attract flies who feed on pollen of these flowers. Typically, no nectar is produced in fly-pollinated flowers. This carrion-scented flower is also known as “Stinking-Benjamin” or birthroot.

red trillium flower. Red trillium (Trillium erectum). Photo by Thomas G. Barnes, USDA PLANTS Database.

A Fly’s Worst Friend

Dogbane is a common pink flowered shrubby herb that flowers in July and August. Dogbane flowers are designed to attract butterflies. When these long-tongued pollinators visit the flowers of dogbane, their tongues become coated with a pollen and cement like mixture from the flower. Flies and weaker insects are not so lucky. These lightweight pollinators often become glued to the flower and die a slow death from starvation.

Dogbane Dogbane. Photo by Brother Alfred Brousseau.

The Midge and the Chocolate Lover

By Beatriz Moisset

What does a midge have to do with chocolate? More than you think. Chocolate comes from cocoa trees. that grow in the tropics. These trees look quite different from most other plants. Instead of having flowers in the most conspicuous places, they have them on the trunk and lowest branches. These flowers are small and white and face down, the reason for all this is that they attract tiny flies, known as midges rather than bees or other better-known pollinators. The midges are ordinarily attracted to fungus; cocoa flowers smell somewhat mushroomy too. In essence, for the cocoa tree to bear fruit, first it has to be pollinated by midges.

Think about it next time that you eat a bite of that marvelous thing known as chocolate. Visit Beatriz Moisset's "The Web of Life" blog…

A candy shop display case stocked with various kinds of chocolate candies. Photo by Beatriz Moisset.