Pollinator gardens have become trendy in recent years, particularly since honey bee losses due to Colony Collapse Disorder started making headlines. Many gardeners and farmers are making an effort to support native bees and attract butterflies to their properties. But people often overlook the other insect pollinators that also deserve our attention. We need to consider rolling out the green carpet in our gardens for these additional 7 insect pollinators (that aren't bees or butterflies).
1. Wasps (Order Hymenoptera)
Although some wasps do visit flowers, as a group they are generally thought to be less efficient pollinators than their bee cousins. Wasps lack the body hairs that bees have to trap pollen, and so aren’t as well equipped for carting pollen from flower to flower.
Still, there are some hard-working pollinators among the wasps. Wasps in the subfamily Masarinae (family Vespidae) are called pollen wasps, and are known to provision their young with nectar and pollen. An orchid called the broad-leaved helleborine (Epipactis helleborine) relies on two Vespula species of wasps – common wasps (V. vulgaris) and European wasps (V. germanica) – for their pollination services. Researchers recently discovered this orchid releases a chemical cocktail that smells like a caterpillar infestation to lure the predatory wasps to their flowers. And perhaps the most notable wasp pollinators of all are the fig wasps (family Agaonidae), which pollinate the tiny flowers inside the developing fig fruit. No fig wasps, no figs.
2. Ants (Order Hymenoptera)
Pollination by ants is relatively rare, but it does occur. Most 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. In addition, ants produce an antibiotic called myrmicacin, which is thought to reduce the viability of the pollen grains they carry. So overall, ants may not be the most effective pollinators.
Still, ant pollinators exist. Formica argentea worker ants have been observed carrying pollen grains between flowers of Cascade knotweed (Polygonum cascadense). Other species of Formica ants distribute pollen among the flowers of elf orpine (Diamorpha smallii, a compact herb that grows on granite outcrops. In Australia, ants pollinate several orchids and lilies effectively.
Photo originally published in Microorganisms transported by ants induce changes in floral nectar composition of an ant-pollinated plant, American Journal of Botany 100(4): 792-800. DOI: 10.3732/ajb.1200626
3. Flies (Order Diptera)
Believe it or not, flies aren't all about landing on dog poop or ruining your Labor Day barbecue with their germy feet. Many flies prefer to feed on flowers, and in doing so, provide essential pollination services to the plants they visit. Nearly half of the 150 Diptera families include flies that visit flowers, so there are bound to be quite a few pollinators among them. Flies are particularly important and efficient pollinators in environments where bees are less active, such as in alpine or arctic habitats.
Among the pollinating flies, hover flies (family Syrphidae) are the reigning champions. The roughly 6,000 species known worldwide are also called flower flies, for their association with flowers, and many are bee or wasp mimics. Some hover flies even have modified mouthparts (called a proboscis) made for siphoning nectar from long, narrow flowers. And as an added bonus, about 40% of hover flies bear larvae that prey on other insects, providing pest control services. Hover flies are the workhorses of the orchard, where they pollinate a variety of fruit crops: apples, pears, cherries, plums, apricots, peaches, strawberries, raspberries, and blackberries.
And hover flies aren't the only pollinating flies out there. Other pollen-toting flies include some carrion and dung flies (which pollinate pawpaws), tachinid flies, bee flies, small-headed flies, March flies, and even blow flies.
4. Midges (Order Diptera)
This may be the most important thing you learn today: no midges, no chocolate. Midges – specifically midges in the Ceratopogonidae and Cecidomyiidae families – pollinate the tiny, white flowers of the cacao tree, enabling the tree to produce fruit. These midges are essential to the production of cocoa, without which we would have no chocolate. And yes, technically midges belong to the order Diptera with the flies listed above, but any insect that is responsible for making chocolate deserves its own mention.
5. Mosquitoes (Order Diptera)
Surprised? Mosquitoes do feed on blood (at least the female mosquitoes do), but they are also partial to nectar. Males drink sugary flower nectar to energize themselves for their swarming flights, when they search for mates. Females also drink nectar prior to mating. And any time an insect drinks nectar, there's a good chance it's going to collect and transfer a little pollen. Mosquitoes are known to pollinate certain orchids, and it's possible they pollinate other plants as well.
6. Moths (Order Lepidoptera)
We tend to give butterflies all the credit as pollinators, but moths do their share of carting pollen between flowers, too. Most moths are nocturnal, of course, and these night-flying pollinators tend to visit white, fragrant flowers, like jasmine. Hawk and sphinx moths are perhaps the most visible moth pollinators. Many gardeners are familiar with the sight of a hummingbird moth hovering and darting from flower to flower. Other moth pollinators include owlet moths, underwing moths, and geometer moths.
Charles Darwin was way ahead of his time when he predicted that a certain orchid with an exceptionally long nectary would require the aid of a moth with an equally long proboscis. Although he was mocked for this hypothesis, Darwin was proven correct when a hawk moth named Xanthopan morganii was discovered using its foot-long proboscis to sip nectar from the comet orchid (Angraecum sesquipedale).
Perhaps the best known example of a moth-pollinated plant is the yucca plant, which requires the help of yucca moths to pollinate its flowers. The female yucca moth oviposits her eggs inside the chambers of the flower. She then collects pollen from the anthers, forms it into a ball, and shoves it down the flower's stigma. The pollinated flower can now produce seeds, Just in time for the yucca moth larvae to hatch and feed on them.
7. Beetles (Order Coleoptera)
Beetles were among the earliest prehistoric pollinators, and they continue providing pollination services to flowers today. Fossil evidence suggests beetles first pollinated cycads. They began visiting flowering plants about 150 million years ago, a good 50 million years earlier than bees. Living beetles seem to prefer pollinating the close descendants of those ancient flowers – magnolias and water lilies, primarily. Although there aren't many plants pollinated primarily by beetles, the flowers that do depend on Coleopteran pollinators are called cantharophilous plants. Cantharophilous plants are often fragrant, giving off spicy or fermented scents that attract their beetle pollinators.
Most beetles that visit flowers aren't there to sip nectar. Beetles often chew and consume parts of the plant they pollinate, and leave their droppings behind. For this reason, beetles are referred to as mess-and-soil pollinators. Beetles believed to provide pollination services include members of many families: soldier beetles, jewel beetles, blister beetles, long-horned beetles, checkered beetles, tumbling flower beetles, soft-winged flower beetles, scarab beetles, sap beetles, false blister beetles, and rove beetles.
- Encyclopedia of Entomology, 2nd edition. Editor John L. Capinera.
- Attracting Native Pollinators, Xerces Society.
- Fig Wasps, US Forest Service.
- The Ecology and Evolution of Ant-Plant Interactions, by Victor Rico-Gray, Paulo S. Oliveira.
- Flies –Pollinators on two wings, The Diptera Site.
- True Flies & Pollination, Texas A&M University Extension Service.
- Pollinating Insects, Idaho State University.
- Animal Pollination, US Forest Service.