A crane fly is a large insect with a short lifespan. The immature larvae can eat up your lawn, but they’re generally not considered a pest. There are a few simple ways to get rid of them.
What Are Crane Flies?
A crane fly, insect family Tipulidae, is a large fly with long, slender legs that looks like a giant mosquito. They’re sometimes called mosquito hawks or skeeter eaters because they’re said to eat mosquitos, though this is untrue.
There are lots of species of crane flies in the United States, but a few types are common and invasive.
Marsh crane fly. The marsh crane fly, species Tipula oleracea, is native to Europe and Africa but is now widespread across North America. These flies are also called the common crane fly.
European crane fly. The European crane fly, species T. paludosa, is also native to Europe and Africa, though popular across North America.
Winter crane fly. This type of crane fly, species Trichocera annulata, is a cousin of the common crane fly but belongs to a different family. It’s smaller and often called daddy long legs, not to be confused with the spider.
What Do Crane Flies Look Like?
A crane fly lays eggs in low-lying areas near water, which hatch as larvae. These larvae are called leather jackets and are brown or gray and cylinder-shaped. They have finger-like projections on one end, no legs, and don’t have a head. Eventually, they become pupae in the soil and emerge as adult crane flies, leaving the casing behind in the lawn.
A crane fly has a body about ¾ inches long, legs about 4 inches long, and a single set of clear wings. They also have antennae called halteres behind the wings that help them fly, though not very well.
Female flies have thicker bodies with pointed tips, and males have pincers. You can tell these flies from mosquitoes by the mouth and wings. Crane flies have snout-like mouths, while mosquitoes have piercing, tube-like mouths and scales on their wings.
What Do Crane Flies Eat?
Leatherjackets, or crane fly larvae, burrow into the soil and feed on your lawn, though some species eat mosquito larvae. Common and European crane flies of the Pacific Northwest eat shoots, roots, and leaves in your lawn.
Adult crane flies sometimes feed on nectar but mostly don't eat anything. They spend their adult life mating and laying eggs and then die.
What Do Crane Flies Do?
Crane fly larvae are part of the natural ecosystem, which means they’re food for some animals and insects like skunks, birds, ground beetles, and fungi. Crane flies can cause significant damage to your lawn, turf, and other grassy areas.
The larvae leave brown patches in the grass as they feed on the roots and cause the grass to diet. Weeds might take over the dying patches, too. Once you have an infestation in your soil, animals like skunks migrate to your lawn and dig for these critters, leaving holes everywhere.
Are Crane Flies Dangerous?
Crane flies aren’t dangerous to humans. Adult flies don’t bite or sting, and they don’t transmit any diseases. They can be a nuisance, though. These flies are attracted to lights and will enter your house at night or get stuck in your screens.
They only have one set of wings, so they’re not great at flying and often flutter around and bump into things. In this sense, crane flies are more annoying than dangerous. While they can quickly damage your lawn, they aren’t harmful to your health.
The chemicals you use to treat your lawn can be dangerous, though. These are poisonous chemicals if ingested and can be especially dangerous for pets and children that play on grass. This might be the most harmful thing about crane flies.
How to Get Rid of Crane Flies
Proper lawn care is the best way to get rid of crane flies. Insecticides are an option but should only be used after you’ve tried everything else. To get rid of crane flies, try these steps.
Soap test for larvae. The first step to getting rid of crane flies is to test your soil and confirm an infestation. You can take some warm, soapy water and pour it over dead patches in your lawn. The soap irritates the larvae and forces them to surface.
Another simple method is to cut out a dead patch of lawn, break apart the soil, and count any larvae. You have an infestation when you have 15 or more larvae in a square foot.
Mow your lawn. One of the best ways to manage crane flies is to keep your grass at 3 to 4 inches in height. A dense lawn encourages other insect communities that will help keep pests at bay.
Drain your soil. Crane fly larvae or leatherjackets thrive in damp lawns. Draining your soil can help remove some of the water and make it harder for them to survive.
Some eggs hatch into larvae in the fall, go dormant over winter in the soil, and then come back to life again in the spring. Watering your lawn less in the spring can help control the larvae.
Treat with nematodes. A nematode is a parasite or worm. One species called Steinernema feltiae feed on crane fly larvae. Adding these species to your lawn can kill 50% of your infestation.
Treat with insecticide. You can use an insecticide, like chlorantraniliprole, carbaryl, or clothianidin, if nothing else works. Apply it in the fall and winter months for the best results. Follow your local state guidelines for safe application.
Use window screens. Adult crane flies might enter your home and be a nuisance. Make sure your doors and windows have screens to keep them out and fix any cracks or holes they might get in.
Bottom Line: Crane Flies Are Harmless to Humans
Crane flies might look big and scary and can destroy your lawn, but they are medically harmless to people. With good lawn care, you can get rid of most crane flies. Keep insecticides out of reach of pets and children and protect your skin and eyes during application.