Crane flies are also known as skeeter eaters or mosquito hawks, but they don't eat mosquitoes.Crane flies are fragile insects that come up in large numbers during late summer. These long-legged flies may look like huge mosquitoes, but they do not bite or sting humans. There are around 4000 species of these insects that belong to the largest family of flies, named Tipulidae.
The size of an adult crane fly may vary with different species. Some species may attain a body length of around 60 to 100 mm. Their length may vary between 0.125 to 4 inches. Some of the smaller species may resemble mosquitoes. An adult male crane fly has two membranous wings, long legs, and a long abdomen, which is thinner with a blunt tip. The abdomen of a female crane fly is thicker and pointed. The sharp tip may look like a stinger, but it is the ovipositor that is used for depositing eggs inside soil, water, and mats of algae. The crane fly has large compound eyes, and a pair of antennae. The number of segments in each antenna may vary with different species. While some species have 11 to 14, others have around 39 segments in each antenna. The smaller species can be distinguished from mosquitoes and other flies, with the V-shaped suture on the back of their thorax.
Crane flies are known by different names across the globe. They are called daddy long legs in Ireland and the United Kingdom. They are also known as gallinipper, gollywhopper, jimmy spinner, mosquito hawk, etc.
The life cycle of crane flies consists of four stages―egg, larval, pupal, and adult stages. Adult crane flies have a very short lifespan. Once they emerge from the pupal stage, these flies indulge in mating. Eggs are laid within a few days. The female crane fly lays black-colored eggs in wet/dry soil, water surface, or mats of algae. Crane fly eggs have a filament-like structure to anchor themselves to the substrate. A single female may lay around 2 to 300 eggs. The eggs hatch within a week or two, and the larvae look like grayish-brown, cylindrical, and legless worms. The body of the larva tapers towards the head. Its body may have small spots, welts, or other projections. In some species, the larvae develop a tough outer covering, so they are called leatherjackets.
The larval stage consists of four instars. In some cases, the larvae overwinter during the third instar and feed voraciously. During the fourth instar, they stop feeding and move deep into the soil. The pupal stage starts within two months. The larval stage gets longer in such cases. Otherwise, the larval stage of crane flies can be as short as a few weeks, after which they start pupating. Even the pupal stage is very short and lasts for a week or two. Adult crane flies have very short lives, so they mate, lay eggs within a few days, and die.
As mentioned above, adult crane flies have a very short lifespan. So, mating and laying eggs are among the main functions. Usually, crane flies are not seen feeding. However, they may sometimes eat pollen and nectar from flowers.
An adult crane fly feeding on pollen
However, crane fly larvae are voracious feeders. They feed on grass roots, seedlings, flowers, fungi, decomposing wood, algae, etc. Larvae of some crane fly species can be carnivorous, and feed on mosquito larvae, small insects, and invertebrates. So, such larvae can be predators too. Some others are shredders as they use their specialized mouth parts to shred their food. Some are gatherers who collect food from animal feces and other decomposing organic material.
When it comes to the diet of crane flies, the main role is played by the larvae, who feed mainly on plant matter. In large numbers, they are considered as pests, and they can destroy grass and other plants. As they eat the roots, the turf may develop yellowing. When pulled, the grass may come out easily, as they have no roots. Such damage occurs during autumn and winter, and worsens during spring, when larvae are fully grown. Predators like skunks and moles may dig up the turf and feed on crane fly larvae. This also causes damage to a great extent.
Though adult flies are not considered as pests, they may become a menace as these insects have the habit of swarming around light sources. Usually, control measures are not required for crane flies and leatherjackets. However, severe leatherjacket infestation has to be controlled with proper pesticides. Biological nematodes are preferred for eliminating crane fly larvae.