Aphid Midges

A midge is a small fly. Most midges are food for frogs and swallows. Many of them eat debris and help with nutrient cycling. Two of them, sand flies and black flies, bite and are vectors for disease. But, aphid midges deserve our notice and appreciation. They eat aphids. They eat a lot of aphids. Once you see how tiny these predators are, you may wonder how they do it. Let’s find out.

A midge feeding on the knee of a mantis, while the mantis eats a bee (JonRichfield) CC BY-SA 3.0.jpeg

Aphid midge description

Adult aphid midges (Aphidoletes aphidimyza) are only 1/8 inch long. This means that you could line up half a dozen of them across the face of an American dime. Aphid midges can be mistaken for large fungus gnats or small mosquitoes. This is understandable since they are all members of the Diptera (two-winged) order, but mosquito wings are thinner than aphid midge wings.

Aphid midge (James Lindsey at Ecology of Commanster) CC BY-SA 3.0

Fungus gnat (B. Schoenmakers) CC BY 3.0

Female mosquito (USDA) CC BY 2.0

Aphid midge larvae look like tiny orange slugs.

Aphid midge diet

Aphid midges feed on more than 70 different aphid species, including the dreaded green peach aphid. And it is the larvae who eat the most. They do this by injecting a paralyzing toxin into the leg of their prey. Then they suck the life juices out through a hole they have chewed in their prey’s thorax, the middle portion. Because their prey is paralyzed, aphid midge larvae can kill insects much larger than themselves. In fact, aphid midges are known to kill more prey than they can eat, but we won’t hold that against them. Aphid midge larvae kill up to 65 aphids each day.

Orange predatory midge larvae among pea aphids (Whitney Cranshaw, Colorado State University) CC BY 3.0 US

Working with aphid midges

February may feel too early to consider aphids (unless you live in the Southern hemisphere). But it’s never too soon to learn how to help your garden plants stay healthy. As temperatures rise, you may want to buy aphid midge pupae to help in your fight against aphids. Pupae arrive in the mail in containers filled with moist vermiculite or peat. Depending on the temperature, pupae emerge as adults in 3–7 days. This is important. You’ll want to time your aphid midge release to coincide with newly emerging aphid populations. If you release them too early in the season, they’ll run low on food.

Before you squish another cluster of aphids, you may want to take a closer look to see if aphid midges aren’t already at work.