The Mysterious (and Brief) Life of Crane Flies

Are those giant mosquitoes?

If you’ve noticed bugs with extra-long legs flying around grassy areas lately, you may be wondering what they are and if you should be avoiding them.

A crane fly (Tipulidae family) sits in a person's hand.
Definitely not a super-sized mosquito.

While their body structure causes them to resemble mosquitoes, they’re actually crane flies. Crane flies are insects in the family Tipulidae. Mosquitoes are in the family Culicidae. While both groups of insects have elongated bodies, wings and long, thin legs, that is essentially where their similarities end. There are thousands of species of crane flies around the world, but none of them have biting or sucking mouthparts. Adults of some species may feed on nectar, but others won’t feed at all in their very brief adult stage, which lasts just a few days.

What we’re seeing now is the emergence of a brood of crane flies that have thus far been living underground as larva. These short-lived adults are busy mating and laying eggs. The female crane fly deposits her eggs in moist soil or algae mats. In just a couple of weeks, the eggs will hatch and the larva will remain in the soil, eating decomposing plants. In fact, crane flies will keep munching on dead plant matter all winter. A relatively warm, wet winter is a crane fly larva’s best friend – especially if you left your leaves on the lawn!

A crane fly (Tipulidae family) sits in a person's hand, showing its profile

The next stage of development is the pupa. This is when the larva becomes inactive with a hard outer covering, like a chrysalis, while it transforms into an adult. Some adults will emerge when conditions are favorable in the spring. Still, others will remain in their larval stage until fall, actually hibernating through the hot, dry summer.

The large numbers of crane flies we’ve seen recently are probably a result of the relatively mild winter of 2019–2020. Only time will tell how the next generation will fare, but let’s hope they do well! They benefit our ecosystem as larva by helping the process of decomposition, and as adults by providing a food source for other animals like birds and bats.

So worry not! Those large flying insects are not looking for a blood meal! In fact, they’re probably not looking for any meal. You can let them go on their way, knowing that these big, spindly bugs are not only completely harmless, but are also doing their part to help our world stay healthy.

Lisa Salehpour
Nature Interpreter, Sharon Woods