The Crane Fly Calamity

It’s a tale of childhood woe: a school yard during lunch time. Rain drums meditatively on the classroom roof and sheets off the verandah gutters into the mists of recollection. Children, as game as they ever were, race the length of the classroom verandahs with cricket bats, their squeals and shouts energising the greyness of the average autumn day. From out of the deluge a lone creature flies falteringly, gangly legs dangling as it drunkenly intercepts the verandah wall. Having found a dry oasis, it lodges spread-eagled under the white roof above where a dozen others of its kind also shelter from the storm. But no less muffled by memory than the massacre that follows is the war cry of the children as they hoist their cricket bats: ‘Kill the mosquitoes!’ The Crane Fly has escaped a watery grave only to meet its fate in the swing of ignorance.

Crane flies are not mosquitoes. ‘Crane fly’ is one of many common names that typically encompasses the families Tipulidae (true crane flies), Limoniidae (Limoniid crane flies), Cylindrotomidae (long-bodied crane flies) and also sometimes Pediciidae (hairy-eyed crane flies), all of which can be included in the superfamily Tipuloidea. Elsewhere in the world, crane flies are known as daddy long legs, gollywhoppers and even mosquito eaters (yet another myth of the  misunderstood Tipulidae, who literally wouldn't hurt a fly). Larvae are often used by fishermen for trout bait, and these immature forms of Tipulidae are colloquially known as leatherjackets. Mosquitoes, on the other hand, fall into the single family of Culicidae. Apart from the larval name of ‘wriggler’, the only variation to their common name is probably just the choice of expletive used to refer to them after being bitten. 

Types of flies referred to as ‘crane flies’, roughly in order from left to right of family relatedness to true crane flies.

Both crane flies and mosquitoes are of the Diptera order (as both have only two wings and a pair of halteres), but they are only related to the extent of the suborder Nematocera. The oldest Tipuloidea fossils date back to around 240 million years (lower Triassic period), while most Culicidae fossils are around 38 thousand years old - though it is thought Culicidae diverged some time during the Jurassic period. Although the relationships within crane flies, like so much else in taxonomy, are under constant review (for the latest, see here), as are the phylogenetic relationships within Nematocera (if you’re so inclined, there’s some bed time reading in this too), the distinctness of crane flies to mosquitoes is not uncertain due to a variety of morphological and biological differences.

A widely accepted phylogeny for the lower Diptera (Nematocera), showing the superfamiliy Culicomorpha (containing Culicidae species) in relation to the superfamily Tipuloidea (containing Tipulidae species).

Both mosquitoes and crane flies are semi-aquatic holometabolous insects, as they have a larval and pupal stage in their life cycle which relies on water. For mosquito species, larvae are found in all kinds of standing water bodies, such as streams, ditches, ponds and puddles, and some species have a relatively high salinity tolerance. Tipulid larvae require moisture so they don’t dry out, but inhabit wet terrestrial habitats such as soil or rotting plants, and are restricted to fresh water. As with many Dipterans, it is when mosquitoes and crane flies are in their larval stage that they show the most perceptibly distinct morphology.

Mosquito larva  floating just under 

the surface of the water facing 

downwards (left) and a bird's-eye 

view of a fat crane fly larva (right), 

head at the top.

Unlike crane flies, mosquito larvae have eyes on either side of an ovoid head, and a ‘moustache’ of bristles above the mouthparts, as well as numerous hair-like projections all over the body. Most species filter microorganisms and organic matter, though some eat the larvae of other mosquito species. The breathing tube near the end of their abdomen is probably the most characteristic structure of Culicidae larvae - it means they float at the surface of the water. Crane fly larvae have breathing siphons at the end of their abdomen and tend to feed on decomposing plant leaves and associated microflora, or munch on the roots of living plants. All life stages of both these insects are important food sources for fish, birds, amphibians and other insects higher in the food chains of the environments they inhabit. 

Different sizes: crane flies can be BIG. 

Mosquitoes will never want to present 

that much of a target.

Granted, adult mosquitoes and crane flies have a superficial resemblance in that they both have long legs. However, compared to body size, crane flies’ legs are much longer than mosquitoes’ legs (compare the second photo of the Culicid to that of the Tipulid at the end of this post). The average crane fly is also quite big, though often Limoniid crane flies will be a similar size to mosquitoes. Some mosquito legs are striped white, so as to seem ethereal. When threatened, mosquitoes will hold one or both of their hind legs above their body in a characteristically curved position (consult the shadow of the first Culicid picture at the end of this post – you might need to duck down slightly to see them on your screen). True crane flies show and do neither of these things. Also, the structure of mosquitoes’ feet allow them to cling to smooth vertical surfaces, while true crane flies have a great deal of trouble with this. They can often be seen bobbing around windows or sliding and scraping along smooth surfaces searching for footholds, while mosquitoes try their hardest not to be seen.

Crane fly flight can be recognised as the kind that will never win any races (i.e. slow, cumbersome and generally erratic) due to their long legs; some crane flies have recognised a lost cause when they are one and taken up flightlessness instead (yes, Chionea species, I’m looking at you). When at rest, true crane flies hold their wings away from their body, while mosquitoes fold their wings. Mosquito wings have thick setae (bristles) along both sides of the wing veins (which make the wings look quite furry under the microscope) and are highly scleritised (hardened) at the base of the wing, unlike Tipulidae. Like all winged insects, crane flies and mosquitoes have unique wing venation that makes them distinct. For example, the subcoastal vein (Sc) ends at the coastal vein (C) in mosquitoes but in crane flies ends at the first radial vein (R₁). Mosquitoes also have just one anal vein (A) while crane flies have two, and crane flies also have a discal cell (dm) that is absent in mosquitoes. 

Wings of Culiseta species versus wings of Tipula species

Though burdened fliers, all crane flies do so uncomplainingly and silently; this is not the case for mosquitoes where some species, such as the tiger mosquito (Ades albopictus), make that dreaded high-pitched whining sound we all know and hate. Male mosquitoes use this sound to locate females; crane flies travel blindly to encounter mates if there are none immediately present after emergence from the pupal stage.

Head morphology - including 
mouth-parts - of a crane fly 
(top) and  penetration of 
the stylets of a mosquito 
(bottom).

If you’re still not convinced that crane flies aren't just overgrown mosquitoes in a good disguise, let the mouth-parts be the clincher for you. There would be no war on mosquitoes if it weren't for the bloodsucking, disease-spreading ways of the majority of females, as permitted by her specialised mouth-parts: a permanently extended, rigid stylet for piercing and sucking (due to elongation of the maxillae and labrum, which remain comparatively short, separate appendages in crane flies), sheathed by a similarly elongated flexible lower lip, or ‘labium’ (also significantly shorter in crane flies). Like male mosquitoes, crane flies of both sexes feed on nectar or not at all, and have a life span of only a few days or weeks. Prolonged rain can mean that crane flies starve to death. 

Further morphological differentiations include that of the antennae, which vary in crane flies but are most commonly moderately short, thin and of thread-like or bead-like form. Mosquitoes have plumose (feathery) antennae. The presence of the ‘transverse V’ or ‘V-shaped mesonotal suture’ - a groove on the thorax between the bases of the wings - is also an identifier of Tipulidae in taxonomic keys.

Both mosquitoes and crane flies have a world wide distribution and there is much diversity across species within both of these families. New Zealand has 15 species of mosquito, with high endemism: only 3 species are found elsewhere. If you want to familiarise yourself on each of the New Zealand mosquitoes, visit New Zealand BioSecure. Crane flies also show high species endemism at a global scale. New Zealand has comparatively more species of crane fly than mosquito (around 600 species) and the most common of these are usually native species from the genus Leptotarsus, often present in gardens. If you want to know more about these or any species of crane fly from any country, you can search at Crane Flies of the World. 

So spread the word! Let crane fly knowledge infiltrate the population in a way similar to but distinctly unlike the spread of malaria in Africa...

...Crane flies are not Mosquitoes. 

A crane fly versus two vantages of a 5-legged mosquito.

I couldn't have written this without:

•  Biology of Tipulidae by G. Pritchard (1987)
• The Anatomical Life of the Mosquito by R. E. Snodgrass (1959)
• Global Diversity of Mosquitoes (Insecta: Diptera: Culicidae) in Freshwater by L. M. Rueda (2007)

Pictures of the different types of crane flies (Tipulidae, Cylindrotomidae, Pediciidae, Limoniidae, Trichoceridae, Tanyderidae and Ptychopteridae) were compiled by me. The phylogeny, Tipula wing venation, Tipula wing image, and Culiseta wing image have all been modified.