Large, gangly insects with long legs, often seen clumsily bumping against windows or hovering near lights, resemble oversized mosquitoes. Their appearance frequently leads to questions about their identity and potential threat.
Unmasking the Mystery Insect
These “giant mosquito looking things” are crane flies, belonging to the insect family Tipulidae. Crane flies possess distinctive physical characteristics, including long, slender legs that are easily detached, a narrow body, and a single pair of membranous wings. While their size varies, most commonly they measure between 0.5 to 0.8 inches, though some species can reach up to 1.4 inches. Their coloration tends to be dull, often appearing brown, black, or pale yellow.
Despite resembling mosquitoes, crane flies are distinct. Both are true flies (order Diptera), but crane flies are considerably larger. Unlike mosquitoes, which often have a humped appearance and fold their wings flat over their backs when at rest, crane flies typically hold their bodies straight and may rest with their wings splayed out or along their back. Their mouthparts also differ from a mosquito’s piercing proboscis.
Dispelling the Danger Myth
A primary concern for many is whether these large insects bite or pose danger. Crane flies are harmless to humans; they do not bite, sting, or transmit diseases. Adult crane flies have non-functional mouthparts or those adapted for sipping nectar or water, not biting.
The female crane fly has a pointed structure at the end of her abdomen, called an ovipositor, which can be mistaken for a stinger. This structure is used solely for laying eggs, typically into moist soil or decaying vegetation. Adult crane flies often have a short lifespan, sometimes only a few days, with reproduction as their main purpose. Their presence in homes is usually accidental; they are attracted to lights and may clumsily fly indoors, causing no harm beyond being a nuisance.
The Ecological Role of Crane Flies
Crane flies undergo complete metamorphosis, progressing through egg, larval, pupal, and adult stages. Their larval stage, called “leatherjackets” due to their tough skin, is significant. These larvae primarily feed on decaying organic matter in moist soil, such as decomposing plant material, roots, and sometimes fungi. Some aquatic species consume leaf debris or algae.
This feeding activity by the larvae contributes to decomposition and nutrient cycling, returning organic matter to the soil. While some species’ larvae can sometimes damage lawns by feeding on grass roots, they are also a food source for various animals. Adult crane flies typically feed on nectar, contributing to plant pollination. Both larval and adult crane flies serve as food for a range of predators, including birds, bats, spiders, and predatory insects, making them an important link in the food web.