Participants in the BYGL Zoom Inservice this past week reported that swarms of crane flies (order Diptera, family Tipulidae) are bellowing up from lawns in Ohio, particularly in the northern part of the state. These large mosquito-like dipterans are also buzzing porch lights and may occasionally find their way into homes to terrorize the occupants.
However, there’s no reason to be concerned unless they are one of the non-native species, but more on that later. Although crane flies look like giant, mutant mosquitoes, they do not possess mosquito-like piercing-sucking mouthparts, so they can’t bite. In fact, the adults are relatively short-lived and they don't feed.
The 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. This may be one reason we’re seeing differences in the crane fly populations in northern Ohio compared to the drier southern part of the state.
Like the adults, the leatherjackets may occasionally appear en masse spilling onto driveways or sidewalks. Such a dramatic appearance 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.
Crane fly adults appear in Ohio lawns and landscapes at two times of the year depending on the species. Some species produce adults in the spring while others generate adults in the fall.
Population densities are heavily influenced by environmental conditions with soil moisture being particularly important. Females use their sharp ovipositors to deposit eggs into the soil. The eggs as well as the resulting leatherjacket maggots are subject to dehydration.
Thus, large numbers of crane fly adults in this fall meant soil moisture levels throughout the previous winter and spring were sufficient to support the survival of the eggs and leatherjackets. Of course, the leatherjackets that pupated and developed into the adults currently buzzing our lawns and landscapes also survived the summer. For that, they employed a nifty survival mechanism that’s used by many other insects to survive inhospitable hot, 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.
However, they can’t remain dormant forever. Aestivating leatherjackets require the return of moist soil conditions in late summer to break out of aestivation and continue their development. Thus, it’s speculated that low soil moisture over the past month in the southern part of Ohio has put the kibosh on crane flies whereas soil moisture elsewhere in the state allowed the leatherjackets to pull through in large numbers.
Although some parts of Ohio are experiencing a bumper crop of crane flies this fall, their activity will eventually subside just as dramatically as their sudden voluminous appearance. 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.
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.
The same cannot be said for two non-native crane fly species that have found their way into North America. 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. Marsh crane flies have 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.
The two non-native crane flies were accidentally introduced into North America from Europe a few decades ago. However, their exact distribution across North America, including Ohio, remains fluid. Thus, it's important to identify exactly which crane fly is billowing from the turfgrass given the destructive nature of the non-native species.
Unfortunately, the two non-native members of the Tipula genus are about the same size and have exactly 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 image below.
However, we would still urge that turfgrass managers send specimens to our OSU C. Wayne Ellett Plant and Pest Diagnostic Clinic (PPDC) for confirmation, particularly if unusual damage to turfgrass has been observed that cannot be explained by a definitive diagnosis. Specimens sent to our PPDC would help us learn more about the distribution of the non-native crane flies.
Here is the hotlink to our PPDC website: https://ppdc.osu.edu/
Please send specimens of 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 crane flies as well as the non-natives.