Crane flies, often mistaken for oversized mosquitoes, are a common sight, particularly during warmer months. Their gangly appearance and large size frequently lead to public concern about their potential to harm humans or gardens. Despite these misconceptions, crane flies are largely harmless insects. This article clarifies what crane flies are and addresses any danger they might pose.
What Are Crane Flies?
Crane flies belong to the insect family Tipulidae, with over 1,500 species in North America. They have long, slender bodies, long, delicate legs, and a single pair of transparent wings. Adults typically range from 0.5 to 1.5 inches in length. While they resemble large mosquitoes, a key distinguishing feature is their lack of a proboscis. Crane flies also have a V-shaped suture on their thorax, differentiating them from other flies.
Crane flies undergo complete metamorphosis, progressing through four life stages: egg, larva, pupa, and adult. Females lay eggs in moist soil or near water. The larvae, called “leatherjackets” due to their tough skin, live underground and feed. They eventually pupate before emerging as adults. Adult crane flies have a very short lifespan, typically a few days to a week, primarily for reproduction.
Dispelling the Danger Myth
Many people mistakenly believe crane flies are dangerous to humans, likely due to their resemblance to mosquitoes. However, adult crane flies do not bite or sting humans or animals. They lack the necessary mouthparts for biting or piercing skin. Most adult crane fly species have greatly reduced mouthparts or none at all, meaning they do not feed during their brief adult stage. If they consume anything, it is typically nectar or water.
Crane flies also do not transmit diseases to humans. Unlike mosquitoes, which can carry pathogens, crane flies pose no health risk. Their presence is generally a nuisance, as they are attracted to lights and may inadvertently enter homes, often appearing clumsy in flight. Their short adult lifespan is primarily dedicated to mating and egg-laying, making them a food source for other animals like birds and spiders.
Crane Flies and Your Garden
While adult crane flies are harmless to humans, their larval stage can occasionally affect gardens and lawns. The larvae, known as “leatherjackets,” live in the soil and feed on decaying organic matter and plant roots, including grasses. In large numbers, these larvae can cause visible damage to lawns, leading to patches of yellowing or thinning grass. This feeding activity often results in brown patches in turf, particularly in early spring when the larvae are most active.
Damage to lawns is typically an issue only when larval populations are very high. Healthy, well-maintained lawns can often tolerate a moderate number of crane fly larvae without significant problems. Not all crane fly species’ larvae are pests; some feed on other invertebrates or decaying wood. The presence of crane fly larvae can also attract animals like birds and skunks, which dig in the lawn to feed on them, sometimes causing additional disturbance.