An Introduction to Craneflies

Insect expert Ben Keywood from Sheffield and Rotherham Wildlife Trust takes a closer look at craneflies.

You’ve probably seen a cranefly recently, though you might know them better as ‘daddy longlegs’. One look at their long, spindly legs and it’s easy to see how they got this nickname! Many of us encounter craneflies when they swarm over lawns and grasslands in late summer and autumn. This is the social event of the season as they look to find a mate, pair and lay their eggs.

Some of our most common craneflies lay their eggs in the soil. Their larvae are known as leatherjackets and they feed on grass roots. This very rarely causes any long-term harm to the grass. Leatherjackets spend up 11 months in the soil before emerging as adults, which will only fly for a couple of weeks before dying. The adults are often attracted to lights, which can sometimes lure them into houses. They’re completely harmless, so be kind and gently encourage them back out into your garden.

Apart from their long, gangly legs, craneflies can be recognised by their prominent 'drumsticks'. These stick out underneath each of their two wings, one on either side of the body. They are in fact modified hind wings, which are reduced to drumstick-like structures called halteres. These act as gyroscopes to maintain balance in flight. Craneflies are closely related to gnats and midges, which also have these halteres – but theirs are less prominent.  

A cranefly, Tipula vernalis, resting on a jagged leaf. The cranefly has a yellowish body and bright green eyes ©Frank Porch

How to identify a cranefly

There are around 350 different species of cranefly found in the UK. The ones we tend to see around our gardens belong to a group known as Tipula, or 'true craneflies'. These are also the largest type of cranefly. They usually rest with their wings held out at right angles to their body, though there is one exception to this rule: Tipula confusa, which rests with its wings over its back. 

Many of the true craneflies look very similar and are difficult to identify. However, you can recognise a female cranefly by its pointed ‘tail’. Male craneflies have square or forked tails. The female’s pointed tail is actually an ovipositor, used to pierce the soil and deposit her eggs.

The largest UK cranefly is Tipula maxima, which occurs in damp moorland and woodland and has beautifully patterned wings. Unlike the garden craneflies, the larvae of this species and several other woodland species live a semi-aquatic lifestyle. They feed under water on living or decaying plants, or in damp moss and leaf litter. 

The other main group of craneflies are called Limonids. Most members of this group rest with their wings over their back, looking a bit like a large midge or mosquito. Unlike some gnats and midges, however, craneflies don't have piercing mouthparts or feed on blood. In fact, adult craneflies rarely feed, but when they do it is on nectar from flowers. 

The largest cranefly, Tipula maxima, resting on a patch of grass and clover leaves ©Frank Porch

Craneflies role in the ecosystem

Craneflies are a vital part of the food chain. Their larvae are a favourite food of starlings, which probe the grass to extract them with their bills. Bats will skim the surface of grasslands at dusk, feasting on the adult flies when they emerge en-masse on warm autumn evenings. Daubenton's bat is particularly fond of them! They’re also eaten by spiders, dragonflies and many other animals.

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