Swarms of crane flies (order Diptera, family Tipulidae) are bellowing up from lawns in Ohio. These large mosquito-like dipterans are also buzzing porch lights and may occasionally find their way into homes to terrorize the occupants.
Crane flies look like giant, mutant mosquitoes. However, they lack mosquito-like piercing-sucking mouthparts, so they can’t bite. There’s no reason to be concerned unless the crane flies are a non-native species capable of causing significant damage to turfgrass.
Like all Diptera (“Di” = two; “ptera” = wing), crane flies only have two functional wings. The two hind wings are modified into knob-like structures called “halteres” which function like biological gyroscopes. The halteres are why most flies are excellent fliers and we call them flies. Sadly, crane flies don’t share their aeronautical talent.
Crane fly adults appear in Ohio lawns and landscapes two times of the year, depending on the species. Some species produce adults in the spring, while others generate adults in the fall.
Adults do not feed, so they must get things over with quickly. Mating and egg-laying occur over about 3 days after adult emergence. The adults may live on for another 7 – 10 days; however, they are living on borrowed time.
Females use their sharp ovipositors to deposit eggs into the soil. The resulting larvae (= maggots) of crane flies are called "leatherjackets" because of their tough, leathery exoskeleton.
The leatherjackets of most crane fly species feed on decaying organic matter in the soil, and they especially appreciate continuously moist areas. Like the adults, the leatherjackets may occasionally appear en masse, spilling onto driveways or sidewalks.
The dramatic appearance of large numbers of crane fly leatherjackets and adults may signal that the lawn has a thatch problem since the larvae are particularly fond of decaying thatch. Although poorly managed Kentucky bluegrass (Poa pratensis) may generate a heavy thatch layer, rough bluegrass (P. trivialis), which is a non-preferred turfgrass, is a notorious thatch producer.
Population densities are heavily influenced by environmental conditions, with soil moisture being particularly important. Consequently, irrigated turfgrass typically produces more crane flies compared to non-irrigated turfgrass.
However, crane flies aren’t necessarily doomed if they encounter dry conditions. Crane fly leatherjackets dodge the dehydration bullet when things heat up and dry out during the summer by entering a form of dormancy, called aestivation. They simply shut down and hole up until environmental conditions became more favorable.
Beware of Non-Native Crane Flies
Our native crane flies cause no damage to the turfgrass or other landscape plants. They serve a valuable function as the "clean-up crew," converting large pieces of organic matter into smaller particles on the way to enriching the soil. Indeed, our native crane flies are considered beneficial insects, nuisance behavior aside.
However, two non-native European expats that have found their way to North America can be highly destructive to turfgrass. The leatherjackets of the European crane fly (Tipula paludosa) and marsh crane fly (T. oleracea) feed on the roots, crowns, and blades of living grass plants, causing serious damage, particularly to turfgrass on golf course tees and greens.
The damage symptoms produced by the non-native crane flies may mimic other turfgrass pests as well as diseases and environmental issues, requiring a close inspection. For example, foliar non-native leatherjacket damage is commonly mistaken for black cutworm (Agrotis ipsilon) damage.
The European crane fly has one generation per year, with adults emerging in late summer to early fall. The Marsh crane fly has two generations per year, with adults emerging in the spring and fall. The fall emergence is typically the largest.
Marsh crane fly females are also much better flyers compared to European crane fly females, which are typically weighted down by a large complement of eggs. Marsh crane flies zoom while the Europeans follow a skip-and-jump flight pattern. The two-generation life cycle, coupled with better flight plans, means the natural spread of marsh crane flies is much faster.
Unfortunately, the two non-native members of the Tipula genus are about the same size and have the same body plan as our native members of this genus. Fortunately, the two non-native species have a distinct white pigmentation running longitudinally on the forewings, as highlighted in the images below.
Take Good Pictures or Send Specimens
It's important to identify exactly which crane fly is billowing from the turfgrass, given the destructive nature of the non-native species. Although the two non-native crane flies were accidentally introduced into North America from Europe a few decades ago, their exact distribution across North America, including Ohio, remains fluid. For example, Curtis Young (OSU Extension, Van Wert County) recently found the marsh crane fly pictured above in northwest Ohio, far from the original introductions in the northeast part of the state.
Although crane flies don’t appear to be great fliers, they can show surprising flight agility to avoid capture. You may find that purchasing a muslin or sailcloth sweep is justified after spending time trying to capture the flies by hand. The lightweight netting of a “butterfly net” will not survive sweeping turfgrass.
Another option is to look for crane flies caught in spider webs. Also, it can be productive to search for crane flies early in the morning when cool temperatures slow their movement.
You will only encounter the marsh crane fly at this time of the year. If you suspect that you’ve captured this non-native, we urge that you send specimens or images to our OSU C. Wayne Ellett Plant and Pest Diagnostic Clinic (PPDC) for confirmation. This will help us to develop a more accurate map of the distribution of this destructive non-native in Ohio.
Please focus your attention on male crane flies, not the females, because males are used for making a definitive identification of the species. Males have abdomens with enlarged, blunted tips. Females have abdomens tipped with a pointed ovipositor. This is true for both our native and the non-native crane flies.
Here is the hotlink to our PPDC website:
https://ppdc.osu.edu/
