Tipula paludosa Meigen Diptera Tipulidae

Natural History

Distribution. The origin of European crane fly or "leatherjacket" is northern Europe, where it occurs from Finland to Great Britain. It was first found in North America in Labrador during 1952, followed by Nova Scotia in 1954, and British Columbia in 1965. The eastern populations have not expanded greatly, but on the west coast the population quickly spread south and east from Vancouver into western Washington and northwestern Oregon.

Host Plants. Larvae feed on numerous plants, though they are generally considered to be pests of pasture and turf grasses. Among vegetables attacked are beet, cabbage, cauliflower, corn, lettuce, pea, potato, rutabaga, turnip and likely others. Other crops such as barley, buckwheat, clover, flax, oat, rape, strawberry, tobacco, and wheat are also reported to be damaged occasionally, and various weeds are eaten. They can persist, but do not thrive, on decaying organic matter.

Natural Enemies. Probably the most important natural enemy of European crane fly in North America is the larval parasitoid Siphona geniculata (De Geer) (Diptera: Tachinidae), which was introduced from Europe. Several pathogens were identified in Europe or North America, including viruses, fungi, and protozoans, but they occur infrequently (Jackson and Campbell, 1975). Moles and birds are frequently cited as predators of leatherjackets, though there is no evidence that they can suppress populations. Weather seems to be more important than natural enemies, with survival or damage favored by cool, wet conditions in the spring and moist conditions in the summer, but negatively affected by cold winters.

Life Cycle and Description. There is a single generation annually, with this insect overwintering in the third instar. Larvae typically become fourth instars in April, pupate in August and then in rapid succession the adults emerge, eggs are deposited, and larvae begin to grow in September. The first two instars are completed by November, when larval growth slows for the winter.

  1. The eggs of European crane fly are shiny purplish black, and elongate-oval. One side is slightly flattened. Eggs measure 1.1mm long and 0.4 mm wide. They are deposited near the soil surface, usually within the upper 1 cm, and must be surrounded by moist soil or the eggs can desiccate. Duration of the egg stage is 11-15 days.
  2. Larvae of European crane fly are called "leatherjackets," and like the larvae of most flies, are nearly cylindrical in form though they taper gradually at each end and particularly toward the anterior end. They are grayish or greenish-brown, and often bear spots. There are four instars. The larva grows from about 3 mm long at hatching to 40 mm at maturity. The duration of first and second instars is about 14 days each. The third instar is several months in duration because the winter is passed at this stage, and the final instar is also about 3-4 month long. Interestingly, during the final 6-8 weeks of larval life the leather-jacket does not feed, and remains relatively inactive. During the final few days of the larval stage, however, the larva descends deeper into the soil and prepares for pupation.
  3. Pupation occurs within the skin of the last instar larva, and so it resembles the mature larva in shape and size. Duration of the pupal stage is 2-3 weeks. When the adult is ready to emerge, the pupa wriggles to the soil surface where the empty puparium remains protruding about 2-3 cm from the soil.
  4. The adults typically emerge at sunset, copulate, and produce eggs all in the same evening.

European crane fly larva.

European crane fly larva.

The adults are fairly small, the males measuring about 14-19 mm long, the females about 19-25 mm. They are narrow-bodied, brownish, with very long legs. Emerging females are incapable of flight, but after depositing most of her eggs they can disperse by flying. Females deposit about 200-300 eggs, nearly all on the night of emergence as an adult. However, adult females can persist for 4-5 days, and males survive even longer, often 7 days.

The biology of European crane fly in North America was described by Jackson and Campbell (1975) and Wilkinson and MacCarthy (1967). Useful publications describing this insect in England include those by Rennie (1917) and Coulson (1962). Barnes (1937b) described crane fly culture. Keys to crane fly genera, including both larval and adult forms, were presented by Alexander and Byers (1981).

Damage

Surprisingly, the larvae feed not only below-ground on the roots and plant crowns, but also climb the foliage at night and attack the leaves and stems. When larvae are numerous, plants may be killed.

Diptera Caudal Spiracles
European crane fly larva, posterior view showing caudal spiracles.
European Crane Fly Larvae
Adult European crane fly.

Management

  1. Larvae can be sampled by washing soil samples through sieves, and they can be flushed from the soil with hot water or salt solutions. Soil samples should be taken to a depth of about 10 cm. The adults are usually sampled by sweeping vegetation with a net, but they also can be captured with light traps.
  2. Insecticides applied to the soil surface in either liquid or granular form is effective to suppress leatherjackets. Larvae also are reported to consume toxic baits (Wilkinson and MacCarthy, 1967).

Cultural Practices. Tillage can be very disruptive to overwintering larvae, though it rarely eliminates all leatherjackets. Flooding is more detrimental to larvae, but more difficult to accomplish. Dry soil is not attractive to ovipositing females.

Biological Control. The nematodes Steinernema bibionis and S. carpocapsae (both Nematoda: Steinerne-matidae), have been shown experimentally to infect larvae of European crane fly (Poinar, 1979), but apparently these potential biological control agents have not been evaluated under field conditions.

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