Last month I featured some wonderful wasps that share our landscapes with us. Continuing on with this theme, this month I want to show you some of the many fantastic flies that call our wildlife gardens home, and why we should appreciate them more.
Flies belong to the very large insect order Diptera, which means having two wings. This is one way to differentiate them from bees who have four wings, especially the fly ‘bee mimics’. They are considered important secondary pollinators, most preferring shallow flowers where they can reach nectar easily. Some pollinating flies, like the bee flies, have longer mouthparts allowing them to reach nectar in complex or tubular flowers.
Flies help keep other insect populations in balance through predation and parasitism. They are used as biological control of agricultural pests such as corn earworm or to pollinate food crops such as carrots.
These tachinid flies are frequent visitors to flowers and feed on nectar with their long, elbowed proboscis. Most lay their eggs on caterpillars where they develop internally feeding on the host, until ultimately, the host dies.
Tachinid flies often have large bristly hairs sticking up from their rear ends. These tachinids also use caterpillars as hosts for their larvae.
Look for these flies in late summer visiting goldenrods, Eupatorium (Joe Pye) species and culver’s root.
Some are considered important pollinators, others feed on the flower resources without transferring pollen to other plants for pollination. Their modified mouthparts allow them to ‘sponge up’ nectar and pollen.
Syrphid fly larvae are voracious predators, predominantly feeding on aphids. Considered an excellent beneficial insect, they help keep aphid populations in balance.
Many syrphid flies are excellent mimics of bees and wasps, helping them avoid predation by birds. If you look and act like a stinging insect, birds will think twice before attempting to eat you for lunch. An excellent survival strategy.
These are also flower visitors, usually seen in late summer.
These flies are common visitors to woodland natives in early spring and are typically found on white flowers. They feed on both nectar and pollen.
This fly resembles a thread-waisted wasp, with an over-sized rear femur. Larvae develop in water-logged wood as well as under wet bark which provides tasty, protein-rich larvae for woodpeckers.
Look for these syrphid flies on bishop’s cap, tall meadowrue, marsh marigold and goat’s beard in the spring.
Both of the next two flies occur on native plants growing close to water where their larvae develop.
Feeds on pollen of Canada anemone. Common near fresh water, where its larvae develop in decomposing plant material and dung.
This shiny blue fly with large red eyes is a frequent visitor to Canada anemone. Larvae develop in water; they have a modified breathing tube which they use to pierce through aquatic plants for an air supply.
Female thick-headed flies are aerial acrobats, some with the ability to parasitize their host (bees and wasps) as they fly through the air, or as they visit plants such as culver’s root.
The larvae hatches and feeds as an internal parasite (usually in the host’s abdomen). The host dies sometime before the larva is ready to pupate; the larva uses the shell of the host as a shelter as it finishes pupation.
Thick headed flies visit culver’s root to feed on nectar.
Bee Fly ~ Family Bombyliidae
Bee flies visit flowers for nectar, their long mouthparts allow them to easily reach into tubular flowers. They hover much like syrphid flies, darting back and forth. They are hairy, resembling small bees.
Look for bee flies in March, hovering around the first bloodroot flowers as well as into the summer months on a variety of native plants.
Bee flies follow their hosts (bees and wasps) back to ground nests where they lay their egg at entrance. Females have a modified abdomen to allow them to scoop up sand into their abdominal chamber where the eggs get coated in sand for protection from the elements. Bee flies also lay their eggs on grasshopper eggs, beetles, flies, butterfly and moth caterpillars. Larvae can be both internal and external parasites, feeding on the host.
March flies have characteristic enlarged front legs or ‘big biceps’. You will find them in early spring visiting flowers or resting on foliage. They are considered good secondary pollinators of fruit trees which flower in early spring.
Their larvae typically develop in vegetation that is decaying, breaking down plant fibers and adding nutrients back to the soil.
Excellent bee mimics, often resembling bumble bees. Robber flies are voracious predators of other insects. They will perch on leaves waiting for their prey to fly by. They have been known to catch insects much larger than themselves such as dragonflies.
A huge and diverse genus of flies, often attracted to “oozing substrates, including fungi, flowers and fruit” (Flies: The Natural History and Diversity of Diptera)
Larvae feed on decaying wood and leaf litter. The small-headed adults visit fruiting fungi. Pictured here in the hyphae of stink horn fungus.
You will find these flies around dung or dead animals. Wonderful recyclers and an important agent in the biological control of forest tent caterpillars, which it lays its eggs on.
Long-legged Fly ~ Condylostylus sp.
These tiny iridescent flies perch on leaves and then run across the leaves in a darting habit. They are predators of smaller insects and like having their photo taken.
What kind of flies do you see in your wildlife garden?
References and Further Reading
Hahn, J. (2009). Insects of the north woods. Duluth, MN: Kollath + Stensaas.
Marshall, S. A. (2012). Flies: The natural history and diversity of diptera. Buffalo, NY: Firefly Books.
Marshall, S. A. (2006). Insects: Their natural history and diversity. Richmond Hill, Canada: Firefly Books.
McAlpine, J. F., Peterson, B. V., Shewell, G. E., Teskey, H. J., Vockeroth, J. R., & Wood, D. M. (Eds.). (1987). Manual of nearctic diptera (Monograph No. 28, Vol. 2).Ottawa, Canada: Agriculture Canada.
Arnett, R. H., Jr. (1993). American insects : a handbook of the insects of America north of Mexico. Gainesville, FL: Sandhill Crane Press.
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