Corydalus cornutus
In 3 days ~40% in a week ~60%
The eastern dobsonfly, Corydalus cornutus, is a large insect in the Corydalidae family. The larvae are known as hellgrammites and are among the top invertebrate predators in the streams in which they live, and are used by anglers as bait.
The eastern dobsonfly is found in most of eastern North America. It is usually found near the swift-flowing, unpolluted streams where its aquatic larvae develop. The origin of the word "dobsonfly" is unclear. John Henry Comstock used the term in reference to this species in his 1897 book Insect Life, but did not explain it. He also mentioned that anglers use the word "hellgrammite" for the aquatic larvae they used as bait, but the origin of this term is also unknown. These common names are still widely used for this and other species of corydalids, and essentially all that is known is that the earliest recorded uses appear to originate in the southern Appalachian region of the US (Kentucky, Tennessee, Virginia, West Virginia), where there were other archaic regional names and variants such as "helgamite", "hojack", "go-devil", and "grampus" (or "crampuss"), all with no definitive source or etymology. The latter... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Great Smoky Mountains National Park | 🇺🇸 United States | |
| 2 | Shenandoah National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Baltimore | 🇺🇸 United States | |
| 2 | Washington | 🇺🇸 United States | |
| 3 | Minneapolis [Saint Paul] | 🇺🇸 United States | |
| 4 | Dallas | 🇺🇸 United States | |
| 5 | Austin | 🇺🇸 United States | |
| 6 | Montreal | 🇨🇦 Canada | |
| 7 | New York City | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report an Eastern Dobsonfly sighting in Shenandoah National Park on a given day, based on 56 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 76th most-seen of the 723 insects we can rate there. Over three days the chance rises to about 40%, and over a week to about 60%, if each day is a fresh chance.
June
In that month about 30% of wildlife watchers report an Eastern Dobsonfly in Shenandoah National Park on a given day, against under 5% in August and October–April, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Eastern Dobsonfly sightings with a recorded time, and about 6 in 10 of them come between 6 am and 6 pm: it is seen both by day and at night.
2nd of 2
Of the 2 parks where we can rate Eastern Dobsonfly sightings, Shenandoah National Park ranks 2nd at about 10%. The best odds are in Great Smoky Mountains National Park (United States, about 20%).
Same family: Corydalidae
The closest relatives of the Eastern Dobsonfly that you can see in Shenandoah National Park (family Corydalidae, Dobsonflies and Fishflies) are Saw-Combed Fishfly (about 10%) and Summer Fishfly (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Eastern Dobsonfly is recorded against all the insects logged in Shenandoah National Park (56 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
