By: Mary Ellen Ellis
Gardeners love a pollinator. We tend to think of bees, butterflies, and hummingbirds as the major critters carrying pollen, but can a fly be a pollinator? The answer is yes, several types, in fact. It’s fascinating to learn about the various pollinating flies and how they do what they do.
Do Flies Pollinate for Real?
Bees don’t have a monopoly on pollinating flowers and responsibility for fruit development. Mammals do it, birds do it, and other insects do it too, including flies. Here are some interesting facts:
- Flies are second only to bees in terms of importance for pollination.
- Flies live in nearly every environment on earth.
- Some flies that pollinate do so for specific species of flowering plants, while others are generalists.
- Flies help pollinate more than 100 types of crops.
- Thank flies for chocolate; they are primary pollinators for cacao trees.
- Some flies look a lot like bees, with black and yellow stripes – like hoverflies. How to tell the difference? Flies have one set of wings, while bees have two.
- Certain species of flowers, like skunk cabbage, the corpse flower and other voodoo lilies, give off the scent of rotting meat to attract flies for pollination.
- Flies that pollinate include many species of the Diptera order: hoverflies, biting midges, houseflies, blowflies, and lovebugs, or March flies.
How Pollinating Flies Do What They Do
Fly history of pollination is truly ancient. From fossils, scientists know that flies and beetles were the primary pollinators of early flowers, at least as long ago as 150 million years.
Unlike honeybees, flies don’t need to carry pollen and nectar back to a hive. They simply visit flowers to sip on the nectar themselves. Carrying pollen from one flower to the next is incidental.
Many fly species have evolved hairs on their bodies. Pollen sticks to these and moves with the fly to the next flower. Sustenance is a fly’s main concern, but it also has to stay warm enough to take flight. As a type of thank you, some flowers evolved ways of keeping flies warm while they dine on the nectar.
The next time you’re tempted to swat a fly, just remember how important these often-annoying insects are to flower and fruit production.
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How Mosquitoes Pollinate Flowers
Although bees are the best known insect pollinators, other insects also are constantly at work transferring pollen from one plant to the next. Flies, moths and even the annoying mosquito are vital links in the reproductive chain of flowers. Little research has been done on the specifics of mosquito pollination, but they have been observed pollinating a few plant species.
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Some wasps do visit flowers. As an insect group, on the whole, they are generally thought to be less efficient pollinators than their bee cousins. Wasps lack the body hairs that bees have to carry pollen and so are not as well equipped for carting pollen from flower to flower. There are, however, a few wasp species that do get the job done.
- There is a hard-working pollinating group among the wasps, the subfamily Masarinae (also called pollen wasps), that are known to feed nectar and pollen to their young.
- Two species of wasps, common wasps (V. vulgaris) and European wasps (V. germanica), provide pollination services to an orchid called the broad-leaved helleborine, also known as Epipactis helleborine. Researchers recently discovered this orchid releases a chemical cocktail that smells like a caterpillar infestation to lure the predatory wasps to their flowers.
- The most notable wasp pollinators are the fig wasps, which pollinate the tiny flowers inside the developing fig fruit. Without fig wasps, there would be a very low likelihood of figs in the wild.
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Pacific Southwest Region USFWS from Sacramento, US/Wikimedia Commons/CC BY 2.0
Pollination by ants is relatively rare, but it does occur. Most ant pollinators can fly, enabling them to distribute pollen grains over a wider area, and thus promote genetic diversity among the plants they visit. Since ants walk from flower to flower, any pollen exchange conducted by ants will be limited to a small population of plants.
Formica argentea worker ants have been observed carrying pollen grains between flowers of cascade knotweed, also known as Polygonum cascadense. Other species of Formica ants distribute pollen among the flowers of elf orpine, a compact herb that grows on granite outcrops. In Australia, ants pollinate several orchids and lilies effectively.
Overall, as a family of insects, ants may not be the best pollinators. Ants produce an antibiotic called myrmicacin, which is thought to reduce the viability of the pollen grains they carry.
I-Pollinate is a citizen science research initiative, through the University of Illinois, Urbana-Champaign, designed to collect state-wide pollinator data. I-Pollinate enlists citizen scientists to participate in three research projects and collect data on monarch egg and caterpillar abundance, pollinator visitation to ornamental flowers, and state bee demographics. Read below to learn more about each pollinator research project and participation requirements. If you are interested in participating and want more information, please fill out our information sign-up form .
Monarch response to garden variability
An important resource for monarch butterflies in their breeding range is milkweed plants, which their larvae need to feed on before they develop into adults. Monarch butterflies in the Midwest experience a wide variety of habitats, and many questions remain about how they respond to the different areas. We are interested in how monarch egg laying and caterpillar growth responds to different garden and landscape variables. We would like citizen scientists to collect data on garden monarch egg and larva abundance in order to better understand how much gardens contribute to monarch conservation.
Pollinator attraction to ornamental flowers
Home and community gardens commonly include a wide array of ornamental and native flower species, and these flowers may provide a variety of floral resources to pollinators. Unfortunately, there is limited information on pollinator attraction to different garden flowers, particularly ornamental annuals. Dr. Harmon-Threatt’s lab at UIUC is currently investigating which ornamental flower species attract pollinators and help create the best environment to host butterflies, bees, and flies. The lab hopes to enlist citizen scientists to observe ornamental flower species and collect pollinator visitation data to evaluate pollinator ornamental floral preferences.
Bee demographics and distributions
Many bee species have experienced population declines over the past decade, and long-term monitoring programs are essential in order to collect baseline bee population data and evaluate changes in bee abundance. This project is part of the larger BeeSpotter program and aims to establish long-term monitoring of Illinois honey bee and bumble bee populations. In order to perform statewide monitoring, we hope to engage citizen scientists across Illinois to take pictures of honey bees and bumble bees. With the help of citizen scientists, we can collect data which will help monitor and conserve honey and bumble bee populations across the state.
Monarch distribution and pollinator attraction projects
The monarch and pollinator attraction projects are done in conjunction, and data collection for these projects requires the installation of a small I-Pollinate research garden . Once the research garden has been set up, participants will need to register their bed online. Then, between June and September participants will spend a week each month collecting flower and pollinator data. Each month, participants will be asked to perform multiple 3- minute pollinator visitation surveys, examine milkweed plants for monarch eggs and caterpillars, and perform a flower survey. Ideally, participants would spend at least 2 hours each month collecting flower, monarch, and pollinator visitation data. However, participants do not need to perform a set number of pollinator or monarch surveys, and participation each month is not required. After data collection, participants will then submit data online or by mail.
Bee distribution and demographics
Participation in BeeSpotter can be done independently or in union with the monarch and pollinator attraction projects. Participants will need to create a BeeSpotter account and then take and submit photographs of honey bees and bumbles bees. More information about getting started with BeeSpotter can be found on the BeeSpotter website .
- In clusters and provide landing platforms
- Brightly colored (red, yellow, orange)
- Open during the day
- Ample nectar producers, with nectar deeply hidden
- Nectar guides present
- May be clusters of small flowers (goldenrods, Spirea)
Many butterflies produce scents that attract the opposite sex. Many of these scents often smell like the flowers that they are attracted to and visit. The scent of these butterfly-pollinated flowers might have evolved as an adaptation that made use of the existing attractiveness of these scents.
Checkerspot butterfly on a cone flower. Photo by Wayne Owens.
Pollinator of the Month: Hoverfly
Despite their tiny size (¼ to ½ an inch) and other anatomical differences from bees including two not four wings and stubby instead of long antennae (see image above… bee on left, fly on right), hoverflies mimic the color patterns of bees and wasps to scare off predators. There are thousands of hoverfly species, all helping to pollinate, yet they don’t sting or bite, and their larvae eat garden pests including aphids and small caterpillars making them beneficial to have around your garden.
Preferred Habitat: Hoverflies are commonly seen in flowering landscapes across the world. They live in decaying wood, on plants, and sometimes in other insects’ nests when food sources are available to the larvae.
Favorite Plants: Fennel, Daisies, Queen Anne’s Lace, Alyssum, Cosmos, Lavender, Zinnias, mint, and other small, flat flowers that allow easy access to nectar.
How They Pollinate: Hoverflies are “incidental” yet crucial pollinators. The adults hover – as their name suggests – like hummingbirds over flowers to drink nectar. When their hairy bodies brush against the flower’s stigmas, pollen is transferred between the fly and flower and vice versa. Although they carry less pollen on their bodies than bees, hoverflies compensate by making a greater number of flower visits. Like bumblebees, most hoverflies are generalists and will visit many different types of plants, however their preference is thought to be for yellow and white flowers.
Superpowers: Hoverflies have the ability to “turn on” and “turn off” their reproductive capabilities based on odors present in nearby plants. The odors hoverflies seek out seem to be related to whether or not there is prey available for the larvae – aphids and other soft-bodied pests. Even in contained environments pregnant females will refuse to lay eggs on non-infested plants. The number of eggs they lay also appears to be connected to how many aphids are present on the plant the hoverfly chooses. Unlike bees and wasps, hoverflies do not supply their larvae with food, and the larvae do not feed from flowers which may explain this unique egg-laying process.
How You Can Help: Hoverflies have stronger populations in places where people plant for all types of pollinators, from butterflies to bees and birds. This helps to build an ecosystem with natural predators and prey for the garden’s inhabitants, and limits the need for insecticides and other harmful pesticides. Cultivating an array of flowering plants will ensure that nectar and pollen are available to pollinators throughout the growing season. You can also try planting different crops in proximity (companion planting) to increase pollination and productivity, while also providing unique habitat for beneficial creatures, including hoverflies.