Hoverfly: Pollinator With Superpowers

Excerpted from: hoverflies: our teeny, tiny pollinators

Hoverflies, also called flower flies or syrphid flies, make up the insect family Syrphidae. As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, while the larvae (maggots) eat a wide range of foods.

Hoverflies are often mistaken for bees. The phenomenon of harmless species mimicking unrelated harmful species as a form of protection from predators. Many hoverflies, which don’t sting, mimic bee species that do making predators think twice before grabbing them.

The superficial similarity continues since hoverflies also pollinate flowers, though not always as efficiently as bees. Hoverflies visit flowers to feed on nectar or nectar and pollen depending on the species. This gives them the energy and nutrients they need to reproduce.

Harmless hoverflies are often mistaken for bees. The phenomenon of harmless species mimicking unrelated harmful species as a form of protection from predators.

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.

Description

  Length: ¼ to ½ an inch
  Wings: 1 pair of wings, they have a isolated vein in the wing between the 3rd and 4th longitudinal veins.
  AntennaeStubby and the last segment bears a strong hair
  Coloration: Black or brown with yellow banded abdomens, resembling wasps
  Diet: Pollen and nectar
  Sting: They do NOT sting

Life Cycle

Adult females lay up to 100 eggs over the course of their lifetime and cannot reproduce unless they have access to pollen as a food source. When the larvae hatch, then feed on pests for a week to ten days or longer then drop to the soil to pupate. Adults emerge after two weeks. Typically there are 3 to 7 generations per year. The pupae will over winter in the soil or in garden debris, emerging as adults in late May or early June.

Reproduction is where hoverflies and bees diverge. Evolutionarily bees and flies diverged a long time ago. Most hoverflies have free-living predatory larvae. Hoverfly adults lay eggs on plants near aphid colonies. The maggots move within the aphid colony grabbing aphids with their mouths and eating them. These are very easy to find if you want to see them in (slow) action.

How Hoverflies Pollinate Flowers

Hoverflies are “incidental” yet crucial pollinators. The adults hover, as their name suggests, like the Ruby Throated Hummingbird 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.

Pollinator Prowess

Hoverfly larvae feed on Aphids, key crop pests. Each summer, one to two generations of larvae hatch. The hungry baby bugs devour aphids as they mature. They likely consume more than 1 million cereal aphids per hectare of arable cropland, the researchers report. That means hoverfly larvae clean up about 20 percent of the typical spring aphid population densities.

Hoverflies also provide key pollinating services to wildflowers, soft fruits and agricultural crops in the mustard family like broccoli, cabbage and rapeseed, the plant that yields canola oil. And they are quite good at it. Hoverflies are frequent flower visitors and their numbers are equivalent to the managed Honey Bbee populations that agriculture currently relies on. Hover flies do not sting.

Hoverfly 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.

Declining Pollinators

Insect populations are in trouble around the globe. But hoverflies appear to be somewhat resilient. Over the last 10 years, hoverfly populations remained fairly constant. Considering that many beneficial insects are seriously declining, our results demonstrate that Hoverflies are key to maintaining essential ecosystem.

How To Attract Hoverflies

  Plant a diversity of flowers
  Choose: alyssum, Aster, Coreopsis, cosmos, daisies, dill, fennel, feverfew, lavender, marigolds, mint, statice, sunflowers, wild mustard and zinnia.
  Provide continual blooming from the last frost til the first frost since hover flies are active throughout the growing season. Plant a variety of flowers to ensure there is always something blooming.
  Leave weeds such as wild carrot and yarrow between crop plants.