Crane Flies

Crane flies are the Rodney Dangerfields of insects. They don’t get no respect from folks who mistake them for giant mosquitoes. They don’t get no respect from fly fishermen unaware of their importance. And they don’t get no respect from entomologists who see no money in them.

Crane flies belong to the family Tipulidae, a name that stems from tippula, the Latin for water spider, and there can be little doubt that trout take the traditional spider dry fly for an adult crane fly. Crane flies range from the tropics to Greenland, and they have even been found at elevations as high as 11,000 feet. About a third of the species is aquatic with the larvae living in streams and ponds. Most of the other larvae live in moist land environments such as damp soil or decaying vegetation.

Life Cycle

Crane flies spend the better part of a year in the larval stage. Soft-bodied and wrinkled, the aquatic larvae look like translucent maggots, and they vary in color from dirty white to green and brown. Some larvae are predaceous, but whether in water or on land, the majority are detrivores (detritus eaters) and play a significant role in the processing of leaf litter, an enormous but generally unrecognized transfer of energy.

Sluggish in movement, the aquatic larvae commonly live and feed beneath accumulations of dead leaves in rivers or streams or on land. Some larvae live in the silt and fine sand in the marginal habitats of streams and slow-moving backwaters. They also dwell in debris caught in logjams, and some species live under stones and mosses in the streambed.

A few species pupate and hatch in the water, but most migrate to the soil adjoining the water to pupate for one to two weeks. Thus, tying pupal imitations has always struck me as an exercise in futility.

Probably no insect shows a greater difference in appearance than the larval and adult crane fly. Legless, most larvae are fat and often have obscenely bloated bodies. Mature larvae of Tipula abdominalis, the Giant Crane Fly, while reaching 21/2 inches long are almost 1/2 an inch in diameter. In contrast, the adults of T. abdominalis, as with all crane-fly species, have slender bodies “with six long legs, all here and there,” to quote the poet Anon. It’s as though Orson Welles metamorphosed into Tommy Tune.

The adults of most species live only a few days with the length of their lives dependent on environmental conditions. Back in 1920, Charles Paul Alexander, the great student of crane flies, observed in his classic two-volume study, The Crane-Flies of New York, “The presence of moisture is almost a necessity in crane-fly development, and consequently the species as adults occur in the vicinity of water, either running, standing, stagnant, permanent, or temporary.”