Issue 10, September 11, 2020

Hover Flies

Hover flies (aka syrphid flies or flower flies) are likely buzzing about any nectar-producing flower in your garden this summer. They are excellent fliers, capable of flying backwards, forwards and hovering over their beloved flowers. They were abundant on my recent camping trip, likely because our camping site was near agriculture fields. They annoyed us as they constantly swarmed and landed on us, presumably looking for moisture and salts on our skin.

Hover flies are yellow and black, and commonly mistaken for bees. They mimic bees and or wasps for protection against predators such as birds. 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, while wasps have four. 

Hover fly Photo Credit: Phil Nixon

Hover flies are one of the most prolific pollinators in Illinois gardens. They feed on pollen, nectar, and honeydew (frass of phloem feeders like aphids). In addition to their pollinator services, their larvae are voracious meat-eaters, feeding on aphids, thrips, scale, caterpillars, and mealy bugs.

Hover fly larva

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. The larvae, which are technically maggots, hatch within two to three days. The larvae are muted green, legless, worm-like, and can be found on the undersides of leaves. 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 mealybug infestation in your garden, be sure to turn over the leaves to look for these beneficial maggots before you spray. 

Kelly Allsup

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