Corydalus cornutus
In 3 days ~10% in a week ~30%
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 |
Rare
Under 5% of wildlife watchers report an Eastern Dobsonfly sighting in Dallas on a given day, based on 46 verified sightings from GBIF citizen-science data. It is the 421st most-seen of the 1412 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
January and June–August
In those months about 10% of wildlife watchers report an Eastern Dobsonfly in Dallas on a given day, against under 5% in February–May and September–December, 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.
4th of 7
Of the 7 cities where we can rate Eastern Dobsonfly sightings, Dallas ranks 4th at under 5%. The best odds are in Baltimore (United States, about 10%), Washington (United States, about 10%) and Minneapolis [Saint Paul] (United States, under 5%).
GBIF citizen-science records
It is estimated from how often the Eastern Dobsonfly is recorded against all the insects logged in Dallas (46 verified sightings), 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.
