Crane flies vary in size, with temperate species ranging from 2 mm up to 60mm, while tropical species have been recorded at over 100 mm.
Female abdomens contain eggs, and as a result appear swollen in comparison to those of males. The female abdomen also ends in a pointed ovipositor that may look somewhat like a stinger but is in fact completely harmless.Adult mouthparts may occur on the end of the crane fly's long face, which is sometimes called a snout or a short rostrum.
Larvae have a distinct head capsule, and their abdominal segments often have long fleshy projections surrounding the posterior spiracles (almost like tentacles).
Despite their common names, crane flies do not prey on mosquitoes as adults, nor do they bite humans. Adult crane flies feed on nectar or they do not feed at all; once they become adults, most crane fly species exist as adults only to mate and die. Their larvae, called "leatherjackets", "leatherbacks", "leatherback bugs" or "leatherjacket slugs", because of the way they move, consume roots (such as those of turf grass) and other vegetation, in some cases causing damage to plants. The crane fly is occasionally considered a mild turf pest in some areas. In 1935, Lord's Cricket Ground in London was among the venues affected by leatherjackets: several thousand were collected by ground staff and burned, because they caused bald patches on the wicket and the pitch took unaccustomed spin for much of the season.
Little is known of the juvenile biology of many crane fly species. The larvae of less than 2% of the species have been described. Of those that have been described, many prefer moist environments, and some leatherjackets are aquatic.
The long legs are an adaptation that may allow the fly to alight in grassy places.
Crane flies are a food source for many birds. They are also susceptible to fungal infections and are a food source for many other insects