Crane flies, with their long legs and slender bodies, are a common sight, often stirring curiosity due to their resemblance to oversized mosquitoes. These insects are generally misunderstood, despite being harmless to humans. They are a widespread group, with over 15,000 described species globally.
From Egg to Adult
The life cycle of a crane fly involves four distinct stages: egg, larva, pupa, and adult, a process known as complete metamorphosis. Female crane flies deposit their eggs in moist soil, often near water sources or in damp lawns. These oval, black eggs, about 1mm long, hatch into larvae within 6 to 14 days.
Crane fly larvae are commonly called “leatherjackets” due to their tough, cylindrical, and legless appearance, resembling worms. These larvae can grow significantly, sometimes reaching up to 4 cm in length. They primarily feed on organic matter in the soil, such as decaying plant material, fungi, and sometimes roots of grasses, and can undergo four molting cycles as they grow. The larval stage can last from a few weeks to up to a year, often overwintering in the soil.
After completing their larval development, crane flies enter the pupal stage, typically occurring just below the soil surface. This stage can last about one to two weeks, though some species may remain pupae for several months. Once metamorphosis is complete, the adult crane fly emerges from the pupal case, leaving behind an empty casing that can sometimes be seen protruding from the soil.
Natural Environments and Human Spaces
Crane flies are typically found in environments characterized by moisture and vegetation. Their preferred outdoor habitats include damp soil, areas with decaying organic matter, lawns, and locations near water sources like creeks, ponds, or marshes.
While crane flies primarily inhabit outdoor environments, they can occasionally be found indoors. Their presence inside human spaces is usually accidental, as they are attracted to lights, especially during the evening. They may enter homes through open doors or windows, or through gaps in screens, seeking warmth. Homes are not their natural breeding grounds. If found indoors, they are often observed fluttering clumsily around lights, trying to find a way back outside.
Dispelling Common Misconceptions
A prevalent misunderstanding about crane flies is that they are “mosquito hawks” or giant mosquitoes that prey on mosquitoes. Adult crane flies are not predators. While some crane fly larvae might feed on the aquatic larvae of mosquitoes, the adult crane flies do not interact with adult mosquitoes in a predatory manner.
Another common misconception is that crane flies bite or sting humans. Crane flies are harmless to people and animals; they do not possess mouthparts capable of biting or sucking blood. Many adult crane fly species have non-functional mouthparts and do not feed during their brief adult lifespan (typically only a few days to two weeks); those that do feed primarily consume nectar from flowers, making them accidental pollinators. They do not transmit diseases to humans. Crane flies play an ecological role, with their larvae aiding in the decomposition of organic matter and nutrient cycling, and both larvae and adults serving as a food source for various animals, including birds, bats, and spiders.