Crane Fly Larva

The crane fly larva, commonly nicknamed the leatherjacket for its tough, leathery outer skin, is the immature stage of the crane fly, a large, long-legged fly often mistaken for an oversized mosquito. While many crane fly species develop in moist soil or lawns, a number of species have larvae that are fully or semi-aquatic, living in the mud, decaying leaf litter, and shallow margins of ponds and slow streams.

Leatherjackets are stout, cylindrical, legless larvae with a tough, grayish-brown skin that gives them good protection as they burrow through mud and organic debris. They are primarily detritivores, feeding on decaying plant material, algae, and organic matter, and in doing so play an important role in breaking down and recycling nutrients within pond and stream-edge ecosystems.

As fly larvae, crane fly larvae undergo complete metamorphosis, eventually forming a pupa before emerging as the adult crane fly, a delicate, long-legged insect that does not bite and is often seen fluttering weakly near lights or vegetation in late summer.

• Thick, cylindrical, worm-like body 20-40 mm long, tapering slightly at both ends, tough and leathery gray-brown skin
• No visible legs, moving instead by muscular contractions of the body
• Small, retractable head capsule that can withdraw into the front body segment
• Rear end often bears small fleshy lobes or spiracle openings arranged around the tip
• Skin notably tough and resistant compared to the softer bodies of many other fly larvae
• Distinguished from horse fly larvae by its blunter, uniformly cylindrical shape and lack of fleshy prolegs along the body

Aquatic and semi-aquatic crane fly larvae are found in wet mud, decaying leaf litter, and the shallow margins of ponds, marshes, and slow-moving streams across much of the world, often burrowing just beneath the surface of saturated soil or sediment. They are most abundant in cooler, moist seasons and can tolerate periodic drying and re-wetting of their habitat better than many fully aquatic larvae.

Crane fly larvae burrow through wet mud, leaf litter, and decaying vegetation at the water's edge, feeding primarily on decomposing plant material, algae, and other organic matter, making them important detritivores within pond and stream-margin ecosystems. Their tough skin offers some protection from the abrasive, wet substrate they move through, and they can withdraw their head into the body for further protection. By breaking down plant debris, leatherjackets help recycle nutrients back into the ecosystem and serve as a food source for birds, fish, and other predators that forage in shallow water and wet soil.

Females lay eggs in wet soil, mud, or shallow water near vegetation. The larvae that hatch burrow into the substrate and pass through four instars over the course of several months to a year, feeding on decaying organic matter and growing steadily, with many species overwintering as larvae. When mature, the larva forms a pupa either within the soil or partly emerged at the surface, and after a period of development the adult crane fly emerges, typically living only a short time as an adult focused on mating and egg-laying rather than feeding.