Crane Flies: Harmless Bugs With a Bad Rap
The crane fly, often called "daddy long legs," is one of the most misunderstood flying insects. Since it resembles the mosquito and is frequently found indoors, it has gotten a bad reputation as a harmful pest. Actually, these flying bugs are often a nuisance, but they do not bite nor do they spread disease. These "daddy long legs" are not to be confused with the common cellar spiders nor the arachnid opilones referred to as "harvestmen."
There are two types which inhabit our homes and gardens: the European crane fly, Tipula paludosa and the common crane fly, Tipula oleracea. The two are visually the same except to the practiced eye of an entomologist. One distinct difference is the number of life cycles per year. Typically, the crane fly emerges as an adult in the late summer/early fall when it mates and lays eggs in the soil of turf grasses. The adult Tipula oleracea also emerges again in the spring when temperatures are warm enough. The females emerge with mature eggs, ready to reproduce. Although they sip nectar, they do not eat. The sole purpose within their short 10-14 day life span is to mate and reproduce. A female will typically lay 300 eggs in the soil.
Crane flies as flying insects are harmless; however, in the larval stage, they can do damage to turf grass when populations are heavy. The leatherjacket, as the larva is known, does feed on the thatch and roots beneath our lawns where it helps with the decomposing of organic matter. Healthy lawns and environments that attract birds and wildlife can withstand this insect, but sometimes, with dense leatherjacket populations, lawns will exhibit unsightly brown spots with poor growth. How can you tell if you have a problem?
It's important to understand that brown spots can be caused by a number of things, including insects, poor irrigation practices, and fungal diseases. It is necessary to diagnose the source of the problem before trying to fix it. The application of soil and turf insect killers and fungicides should be done as a last resort since these things will indiscriminately kill all insects and fungi under your lawn, including beneficial ones.
Larval Turf Pests
How to Find and Control the Crane Fly
Follow these simple steps to check for a crane fly larvae problem:
- Choose 3–4 areas in your lawn for sampling. Observing the places where birds or wildlife are feeding can help you to pick likely spots.
- Measure an area approx 6"x6" and use a knife to remove a plug 3" thick.
- First, look in the hole for larva, then examine the mass you've removed. Larva will usually be visible in the root and thatch area. Pull the clump apart lightly. If it is easy to tear, it's a good sign that larvae have been chewing on the roots.
- Count all of the larvae and multiply x 4 to determine the number per square foot.
- Repeat these steps in the other 2–3 locations.
There are apt to be other larvae in your sod such as cutworms, beetle grubs, and sod webworms. Leatherjackets are distinctly legless.
If your lawn is healthy, and you've found between 25 to 40 per sq. ft., you really needn't worry about treatment. Birds, small mammals, frogs, and subterranean beetles help keep the populations under control. If you've counted 50–100 per sq. ft., you may want to treat the lawn. There are granular insecticides and those applied through a hose-end sprayer. Most contain imidacloprid or cyfluthrin and target these pests plus a host of other soil and turf insects including grubs, fleas, chinch bugs, mole crickets, ticks, and ants. As an organic alternative, there are beneficial nematodes which are available for home delivery through www.tiptopbio.com or other suppliers in your area.
A Word About Pesticides
Try to avoid neonicotinoid pesticides which kill our bees such as cyfluthrin and imidacloprid. Consider attracting birds and wildlife (the worm's natural predators) instead, or opt for organic controls.
It may be a nuisance to find that raccoons and skunks have been grub-hunting in your lawn, but they are actually helping. Placing garden netting with lawn staples in these areas at night will dissuade them. They don't like to get their feet tangled in it.
Remember to look at the larger picture. We share our environment with many other things, and the beauty around us is a product of a collaborative effort. Take the time to understand the presence of "pests" before attempting to eliminate them. They are usually minor inconveniences of short duration such as the crane fly which doesn't deserve its bad rap!
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
How come crane flies in my house don't move?
Craneflies often rest unless disturbed. Sometimes the wings are opened, and sometimes not.Helpful 24
Will crane flies reproduce in the carpet if indoors?
No. They mate and lay eggs in the soil where the hatched larvae eat turf grasses and roots.Helpful 3
Do crane flies kill flies in your home?
No. The only purpose of an adult cranefly is reproduction. In its short life of several days, it must mate and deposit eggs in the soil. It doesn't eat.Helpful 19
What do crane flies eat?
The only purpose of an adult crane fly is to mate and lay eggs. It has a life span of a few days and does not eat except for small amounts of nectar. Only the larva, known as leather jackets, feed.Helpful 16
Why do the legs of crane flies become lame or fall off?
Even though crane flies live for 2 weeks, their purpose is to mate and reproduce. Their six legs are nearly twice as long as their bodies and act to protect them. It is much easier for a predator to grab the long legs than it is to reach the body, and the crane fly has the ability to drop one leg or more as a means of escape. This is called autonomy. Centipedes and other long-legged insects and arthropods have this capability as do lizards which drop their tails when threatened.Helpful 13
© 2011 Catherine Tally