Crane flies, often mistaken for giant mosquitoes, are a common sight in many gardens and yards. Belonging to the insect family Tipulidae, these long-legged creatures frequently cause curiosity and sometimes concern. While their larvae, known as leatherjackets, can occasionally be a nuisance to lawns, adult crane flies are generally harmless and play a part in the ecosystem. Let’s delve into the world of crane flies to understand what they actually do, separating fact from fiction.
Crane Fly Identification: Beyond the “Giant Mosquito” Misconception
Often dubbed “mosquito hawks” or “skeeter eaters,” crane flies are mistakenly believed to prey on mosquitoes. This is a myth. While they might resemble oversized mosquitoes, especially with their slender bodies and long legs, adult crane flies have very different mouthparts and feeding habits.
There’s a wide variety of crane fly species in regions like North America. Some of the more frequently encountered types include:
Marsh Crane Fly ( Tipula oleracea): Originally from Europe and Africa, this species has become widespread in North America and is also known as the common crane fly.
European Crane Fly (T. paludosa): Similar in origin to the marsh crane fly, the European crane fly is also prevalent across North America.
Winter Crane Fly (Trichocera annulata): A smaller relative of the common crane fly, the winter crane fly is sometimes called “daddy long legs” – a name that can cause confusion with cellar spiders.
Alt text: Close-up of a marsh crane fly, Tipula oleracea, showcasing its slender body and long legs, commonly found in North America.
What Do Crane Fly Larvae (Leatherjackets) Do? The Lawn’s Underground Inhabitants
Crane flies begin their life cycle as eggs laid in damp, low-lying areas, often near water sources. These eggs hatch into larvae, commonly known as leatherjackets. These larvae are brown or gray, cylinder-shaped, and lack legs or a distinct head. They are characterized by finger-like projections on one end of their body.
Leatherjackets live in the soil and are known for feeding on the roots and stems of plants, including grass. This feeding habit is why they can sometimes be considered lawn pests, as significant infestations can damage turf.
Alt text: Leatherjacket larvae, the immature stage of crane flies, depicted in their typical brown and cylindrical form, highlighting their subterranean habitat.
What Do Adult Crane Flies Do? Debunking the “Mosquito Hawk” Myth
Adult crane flies emerge from pupae in the soil, leaving behind their casings in the lawn. They are characterized by a body length of about ¾ inches and remarkably long legs that can reach around 4 inches. They possess a single pair of clear wings and halteres, antennae-like structures behind the wings that aid in their somewhat clumsy flight.
Adult crane flies have snout-like mouths, unlike the piercing, tube-like mouths of mosquitoes. This difference in mouth structure is a key indicator that crane flies do not feed on blood like mosquitoes. In fact, many adult crane flies do not feed at all, or they may consume nectar from flowers. Their primary purpose in their adult stage is reproduction. They are short-lived, with their adult lifespan focused on mating and laying eggs to continue the cycle.
Distinguishing between male and female crane flies is possible by observing their body shape. Females tend to have thicker bodies with pointed abdomens, while males have pincers at the end of their abdomen.
Alt text: Visual comparison of male and female crane flies, emphasizing the thicker body and pointed abdomen of the female versus the pincer-like abdomen of the male.
Crane Flies: Harmless Helpers, Not Mosquito Predators
In conclusion, adult crane flies are largely benign insects. They do not bite, they do not eat mosquitoes, and their primary activity is focused on reproduction. While their larval stage can sometimes cause minor lawn damage, they are generally not considered significant pests. Understanding what crane flies actually do—primarily existing in their adult stage to reproduce and having larvae that feed on decaying vegetation and plant roots—helps to dispel myths and appreciate their true role in the environment.
