Are Crane Flies Beneficial or Harmful?

Chances are, you have seen large, mosquito-like insects flying around your yard or resting near a porch light.

There is no need to panic. They are probably crane flies. Adult crane flies do not bite or sting, and they do not spread diseases to people.

Crane flies are part of the natural food web. Their larvae may break down dead plant material or provide food for other animals. However, not every crane fly benefits a lawn. The larvae of a few species can feed on grass roots and cause damage.

In this article, you will learn how to identify crane flies, understand their role in nature, and make your yard friendly to wildlife without creating mosquito problems.

Identification

Adult crane flies have slender bodies, narrow wings, and six very long legs. Because of their shape, people sometimes mistake them for giant mosquitoes.

Crane flies are sometimes called tipple flies, mosquito hawks, or mosquito eaters. However, the names “mosquito hawk” and “mosquito eater” are misleading [1]. Adult crane flies do not hunt or eat mosquitoes. Many adults do not feed at all. Those that do feed may sip nectar, water, or other liquids.

Crane fly larvae are often called leatherjackets because they have tough outer skin. They are brown or gray, have no legs, and usually live in damp soil, wet leaves, decaying wood, or water.

The larvae do not all eat the same things. Many feed on dead and decaying plant matter. Some prey on small aquatic animals, while others feed on living plant tissue. The larvae of a few species can damage lawns by eating grass roots, crowns, and shoots.

Are Crane Flies Harmful?

Adult crane flies are harmless to people and pets. They do not bite, sting, or spread disease.

Despite their long legs and awkward flying, crane flies are not aggressive. They may accidentally bump into people, walls, or windows, but they will not attack you.

Although the adults are harmless, the larvae of some species can become lawn pests. They may cause thin grass or brown patches when many larvae feed in the same area. This problem is most common in cool, wet places and does not happen with every crane fly species.

This problem is most common in cool, wet places and does not happen with every crane fly species [2].

The Benefits of Crane Flies

Crane flies do not control mosquito populations, but they still have a place in a healthy ecosystem.

Many crane fly larvae help break down dead plant material. Crane flies also provide food for birds, fish, spiders, bats, frogs, and other animals.

1. Provide Food for Wildlife

Crane flies provide food for many animals. Birds, spiders, bats, frogs, fish, and other predators may eat the adults or larvae.

Aquatic crane fly larvae provide food for fish and other water animals. Some also help break down dead leaves and other plant material in streams and ponds.

2. Help Break Down Dead Plant Material

Many crane fly larvae live in damp soil, leaf litter, rotting wood, streams, or other wet places. Some feed on dead leaves and other decaying plant material.

As they feed, they help break this material into smaller pieces. This supports the natural recycling of nutrients in soil and water.

Crane flies spend much of their lives as larvae. The length of this stage varies widely depending on the species, temperature, food, and habitat.

3. May Visit and Pollinate Flowers

Some adult crane flies sip nectar from flowers. As they move between flowers, they may carry pollen and help with pollination. However, many adult crane fly species do not feed at all.

Crane flies are usually less noticeable as garden pollinators than bees and butterflies. Their role varies depending on the species and habitat.

How to Make Your Yard Friendly to Crane Flies and Other Wildlife

You do not need to create standing water or keep your lawn very wet to attract crane flies. Those steps can encourage mosquitoes or increase the risk of lawn damage.

Instead, use these safer ways to support crane flies and other small animals:

• Grow a mix of native grasses, flowers, shrubs, and trees.
• Leave a small amount of leaf litter beneath shrubs where it will not smother plants.
• Leave a small log or fallen branch in a quiet wildlife area, away from your home and other wooden buildings.
• Avoid using broad insect-killing sprays unless they are truly needed.
• If you add a pond, use a pump or fountain to keep the water moving. Remove nearby containers that collect still water, since mosquitoes can breed in them.
• Reduce outdoor lighting when it is not needed. Bright lights can attract and confuse crane flies and many other nighttime insects.
• Water your lawn only when necessary. Constantly wet soil may support high numbers of lawn-feeding crane fly larvae.

A yard with different plants and natural hiding places can support many insects and animals. You do not need to attract large numbers of one particular insect.

Anything Else That’s Worth Knowing?

Crane flies are weak and awkward fliers. They often bump into walls, windows, lights, and people by accident.

They may enter homes through open doors or damaged window screens. If you find one indoors, place a cup over it, slide a piece of paper underneath, and release it outside.

Adult crane flies usually live for only a short time. During this period, they mate and reproduce. Their exact lifespan and the number of eggs they lay vary by species. Females of some species can lay hundreds of eggs in damp soil or other suitable habitats.

There are thousands of crane fly species around the world [3]. They differ in size, color, habitat, diet, and life cycle. Their long legs and narrow bodies help people recognize them, although some smaller species may not look like the familiar giant “mosquito hawk.”

Takeaway

Adult crane flies may look like giant mosquitoes, but they do not bite, sting, or spread disease. They also do not hunt mosquitoes.

Many crane fly larvae help break down dead plant material, and both adults and larvae provide food for wildlife. However, the larvae of a few species can damage lawns.

There is usually no reason to kill an adult crane fly that wanders into your yard or home. If one enters your home, gently capture it and release it outside.

Image credit: “Primeval” by David Illig, licensed under CC BY 2.0.