Lifespan and Life Cycle of a Crane Fly

Crane flies (AKA ‘daddy long legs’ or ‘mosquito hawks’) are a type of large, fragile fly. Despite looking like big mosquitoes, they don’t bite. In fact, they don’t do much of anything – most species don’t even eat!

This is because the adult crane fly is a very short-lived bug, only surviving a few days after they emerge from their pupae. They show up, bug everyone, breed, lay eggs and die, often within a 24-hour window. But what about the rest of the crane fly life cycle? Where do these spindly insects come from, and how long does it take them to reach adulthood?

What are crane flies?

The name ‘crane fly’ refers to any member of the Tipulidae family, a group that includes over 14,000 insect species. Crane flies are large and gangly-looking, with tan bodies and long, spindly legs, and are sometimes called ‘daddy long legs’ or ‘mosquito hawks.’ They tend to show up in late summer and fall and, though short-lived, have a habit of bugging people by flying into houses. They don’t bite people, or feed on other bugs. If they eat anything at all, it’s usually nectar. Their entire purpose as adults is to find a mate, breed, and lay more eggs – a process that takes no longer than a couple of days.

What is the life cycle of a crane fly?

Crane fly eggs

Adult crane flies emerge in late summer, and spend most of their brief adulthood mating. Female crane flies will lay eggs within 24 hours of emerging from their pupae, which they usually deposit in turfgrass.

Crane fly larvae

Crane fly eggs hatch into legless, grub-like larvae. They are brown, gray or greenish in color, with plump, segmented bodies, a distinct head, and several fleshy projections sticking out of their rear end.

Crane fly usually spend months in their larval form, feeding on turf roots and crowns, and decomposing organic matter throughout the fall and spring.

Some species of crane fly may spend up to five years as larvae.

Crane fly pupae

Eventually, the crane fly larvae pupate in mid- to late spring. Crane fly pupae have tough, brown cases, which is why they’re often called ‘leatherjackets.’ They are usually found just beneath the surface of the soil.

Crane fly adults

Crane fly adults emerge from their pupae in late summer or fall. The adult insects spend the entirety of their short lives mating or laying eggs, which the females will typically do within 24 hours of emerging.

As adult crane flies typically only live for a few days, many species do not eat, though some are believed to feed on nectar from flowers.

How long do crane flies live?

The entire life cycle of the crane fly typically takes around a year, though most of this time is spent in the larval and pupal stages. Adult crane fly only live a few days – just long enough to mate and lay eggs. The adult insects are so short-lived that many species don’t even eat.

Are crane flies harmful?

Adult crane flies are completely harmless to humans and animals and, despite looking a bit like enormous mosquitoes, they don’t bite, sting or spread diseases. However, they are widely considered a nuisance, largely because of their tendency to find their way indoors.

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Crane fly larvae are also harmless to people, but may cause damage to turf grass. This is because they feed on the roots and crowns of turf, and may make a mess of your lawn if present in large numbers.

Crane fly larvae control

Crane fly larvae are rarely a serious issue, unless they are present in very large numbers. For this reason, they are more commonly considered a pest on golf courses, where they may cause large, brown patches to appear in turf.

Maintain your lawn

Crane fly prefer to lay their eggs in moist conditions, so keeping your lawn trimmed and dry will minimize the likelihood of an infestation. If areas of your lawn are prone to accumulating water, find ways to improve drainage.

Biological control methods

Encourage the presence of birds and other insects (such as beetles) in your garden, as these natural predators can help to keep your crane fly population under control. Releasing parasitic nematodes (such as Steinernema feltiae) into your yard can also help to reduce the number of crane fly larvae in your lawn.

Insecticidal control

Insecticides may be used to kill off crane fly larvae, but this method of control is rarely recommended. Insecticides often damage populations of non-target insects, and can be a disaster for the ecology of your garden (and that of the surrounding environment).

Furthermore, chemical control methods may be hazardous to pets, other wildlife species and humans.

Conclusion

Crane flies may be a nuisance when they find their way indoors, but these large, fragile flies are completely harmless to humans. Their larvae may chew through turf roots and crowns, but rarely cause significant damage unless present in very large numbers.

The complete life cycle of the crane fly takes around one year to complete (though it may take longer in some species). Most of the crane fly’s life is spent underground, in larval or pupal forms. Once the adult insects emerge in late summer or fall, they typically only live for a couple of days – just long enough to fly and mate. The adult flies are so short-lived that most species don’t even require food, though some are thought to sip nectar from flowers.

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