Hover flies (aka syrphid flies or flower flies) were likely buzzing about any nectar-producing flower in your garden this summer. These flies, commonly mistaken for bees, are one of the most prolific pollinators in the Illinois garden, according to University of Illinois Extension horticulture educator Kelly Allsup. In addition to their pollinator services, their larvae are voracious meat eaters.
Hover flies are excellent fliers, flying backwards and forwards and hovering over their beloved flowers. Hover flies are yellow and black bee-mimics that feed on pollen, nectar and honeydew (frass of phloem feeders like aphids). They mimic bees and or wasps for protection against predators such as birds. Allsup says they can be easily distinguished from bees because they are shiny and bees are fuzzy. They can be distinguished from wasps in that they have two wings and wasps have four. Sandy Mason, state master gardener coordinator, simplifies it with the saying, “Count the wings. Two wings: fun; four wings: run!”
With many generations per growing season, hover flies are here to stay. The female hover fly will usually lay her eggs on or near aphid colonies and in two to three days the larvae will hatch. “The larva, which is technically a maggot, is muted green, legless, worm-like, and can be found on the undersides of leaves eating aphids, thrips, scale, caterpillars and mealy bugs,” Allsup says. “These larvae are great garden warriors and can be put in the same category as ladybugs and lacewing larvae in terms of the effectiveness in demolishing an aphid population. The larvae grasp the prey with their jaws, hold them up in the air, suck out their body contents and toss the exoskeleton aside.”
According to Cornell University, the larvae can eat up to 400 aphids. The larvae feed for about seven to ten days before they pupate, which takes about 10 days. “Therefore, if you see an aphid or mealy bug infestation in your garden, be sure to turn over the leaves to look for these beneficial maggots before you spray,” Allsup says.
The University of Minnesota just released a trial garden report on flowers that attracted pollinators and listed several annuals as excellent additions to lure hover flies to your garden. Zinnias were number one in attracting these fly pollinators, followed by ‘Tangerine Dream’ and ‘Bambino’ marigolds. The list also included Salvia ‘Coral Nymph,’ Rudbeckia ‘Irish Eyes,’ sunflower ‘Lemon Queen,’ and snapdragons as top attractors.