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.  

Winging it

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. 

A flying feast

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.

Winged invaders?

In autumn you might see a few of these long-legged insects in the home, says Karl Curtis, Director of Nature Reserves for Warwickshire Wildlife Trust:

"They might look like spiders, but craneflies are a really good food source for birds; they're really important so people should let them out their windows and not kill them. The reason craneflies come into the house at this time of year is for warmth and they are attracted to light so if the lights are on in the house they will come inside, and they hatch out in the darker hours to avoid being eaten by birds. They're not looking for shelter, they're out looking for a mate and then looking to lay eggs, they end up in houses because their favourite habitat is short grass and many people have lawns."