Crane Fly

Crane Flies look like giant mosquitoes, but are really just big (about one to two inches long), clumsy flies and do no harm — they neither bite, sting, nor feed... their only purpose is to mate and lay eggs, like many adult insects (and other organisms for that matter). Those most commonly found in Davis are the Turfgrass or European Crane Fly (Tipula paludosa). Though crane fly larva can be an agricultural pest in areas of high moisture, larva are not much of a problem here, and the adults are little more than a bedroom nuisance in warm dry inland areas. Because they are attracted to light, like moths, we typically get to enjoy them in the evenings when they join us indoors. In addition, winter crane fly larva are considered forensically significant under certain circumstances.

Despite the common name of "Mosquito Hawk" and "Skeeter Eater", these large flies unfortunately don't help to reduce the mosquito population. The name possibly comes from the resemblance to mosquito (which shares a taxonomic group with the crane fly, Nematocera) and their large size, compared to the mosquito.

Crane flies grow to about 2.5 inches long with a 3 inch wingspan. Grayish-brown and slender, it's their long thin legs and the way they dance about that many people find most disturbing. Like daddy long leg spiders, their legs are about twice as long as their bodies. In their adult form, crane flies only live for a couple of days and do not usually feed. Adults emerge from the soil beneath grassy areas in late summer and fall, mate, and females lay eggs within 24 hours. Crane fly eggs hatch into small, brown larvae with tough skin; these leatherjackets feed on the roots and eat decaying plants, dead leaves, fungi, and plant roots during the fall before overwintering in the soil. When the weather warms in spring, larvae resume feeding. During the day larvae mostly stay underground, but on damp, warm nights they come to the surface to feed on the aboveground parts of many plants. When mature, the larvae are a little over an inch long. Around mid-May they enter a nonfeeding pupal stage and remain just below the soil surface. In late summer, pupae wriggle to the surface and a single generation of adults emerges each year. Reaching adulthood en masse, one can see swarms of males "dance" above treetops looking for females with which to mate.

Crane flies have many predators. Larvae and pupae are dug up by skunks and moles while aquatic larvae are eaten by fish, turtles, and other underwater predators. Adult crane flies are eaten by birds and bats. From an aquatic perspective, crane flies are indicators of decent water quality, i.e. water that isn't too polluted, but probably has some degree of turbidity and stagnation — for more on benthic macroinvertebrates, see kywater.org.

Visit the UC Integrated Pest Management site for additional information on crane flies and control mechanisms. Visit our Town Wildlife page to learn about other bugs and such inhabiting Davis.

2011-04-13 12:49:46   Thank you for the informative page! —DanielleC