Invertebrates
Crane Fly
Tipulidae · also called mosquito hawk, mosquito eater, daddy longlegs
The big, clumsy, long-legged insect that gets into the house on an autumn night and ricochets off the walls is a crane fly. It is widely believed to be a giant mosquito that hunts other mosquitoes. It is neither dangerous nor a hunter, and many crane flies cannot eat at all.
Overview
Crane flies are the family Tipulidae, one of the largest in the true-fly order, with over 15,000 species worldwide. The larvae eat roots, rotting wood, and leaf litter in damp soil and fresh water. Most adults do not feed, often lacking working mouthparts, and live only a few days to mate and lay eggs.
The mosquito myth
Despite the names mosquito hawk and mosquito eater, the crane fly does not hunt or eat mosquitoes, or anything else. It has no sting, no biting mouthparts, and no venom, and is completely harmless.
Leatherjackets
The tough-skinned soil larvae, called leatherjackets, chew grass roots and can kill patches of lawn and pasture. They are also a major food for starlings, rooks, moles, and skunks.
Status
Not Evaluated as a group and abundant on every continent except Antarctica, though some species tied to particular wetlands or old forests are localised.
Crane Fly: common questions
Do crane flies eat mosquitoes?
No. This is the origin of the names mosquito hawk and mosquito eater, and it is a myth. Adult crane flies are not predators. Many species have no functional mouthparts at all and cannot eat anything; the rest at most take a little nectar or water. The adult's job is to reproduce quickly and then die, usually within a few days. Nothing about the crane fly controls mosquito numbers. The confusion comes purely from the resemblance, since a crane fly looks like a mosquito scaled up several times, with the same slender body, narrow wings, and dangling legs.
Can a crane fly bite or sting?
No. A crane fly has no sting and no biting mouthparts capable of piercing skin, and it carries no venom. It is completely harmless to people and pets. Some species have a long, pointed tip to the abdomen, which is an egg-laying tube in the female or a clasping structure in the male, and this is sometimes mistaken for a stinger, but it cannot hurt you. The insect's habit of blundering into faces and lights and bouncing off walls makes it a nuisance indoors, but that is the extent of the problem.
What are leatherjackets, and why do they wreck lawns?
Leatherjackets are the larvae of crane flies, legless grey-brown grubs with a tough leathery skin, living in the top few centimetres of soil. They feed on the roots and the base of the stems of grasses and other plants, and where they are numerous, often in damp lawns and pastures after a wet autumn, they can kill patches of turf, which then peel back easily or get torn up by birds and mammals digging for the grubs. A brown, dying patch of lawn in late winter that lifts like a carpet and is full of probing starlings usually has a leatherjacket problem underneath.
Why are there suddenly so many crane flies, and then none?
Because the adults all emerge, breed, and die within a short window. A generation of leatherjackets develops in the soil over months, then transforms and climbs to the surface as adults over just a few days when conditions are right, often a mild, humid spell in late summer or autumn. Those adults live only a week or two, spend that time mating and laying eggs, and then die together. The result is a brief flush of crane flies on walls, at windows, and around lights, followed by their near-total disappearance until the next generation matures.