Helophilus fasciatus
In 3 days ~10% in a week ~30%
Helophilus fasciatus (Walker, 1849), the narrow-headed marsh fly, is an abundant species of syrphid fly observed throughout the United States and Canada. Hoverflies can remain nearly motionless in flight. The adults are also known as flower flies for they are commonly found on flowers, from which they get both energy-giving nectar and protein-rich pollen. The larvae of this genus are associated with wet decaying organic material, particularly accumulations of decaying vegetation in ponds and mud and farmyard manure or silage. The adults of this species lays eggs on vegetation overhanging the water. The larvae hatch and drop into the water.
For terminology Speight key to genera and glossary Length, 13–15 mm (0.51–0.59 in) The male is dichoptic. The male's face is yellow and thickly yellow pollinose, with the middle line broadly shining reddish yellow to ferruginous but never black. The pile is pale yellowish. In profile, the face is concave on the upper three-fifths, convex below this, and the lower two-thirds convex receding, without distinct tubercle although the formation approaches one. The frons is narrowed above, and the upper portion is... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Isle Royale National Park | 🇺🇸 United States | |
| 2 | Point Pelee National Park | 🇨🇦 Canada | |
| 3 | Riding Mountain National Park | 🇨🇦 Canada | |
| 4 | Acadia National Park | 🇺🇸 United States | |
| 5 | Shenandoah National Park | 🇺🇸 United States | |
| 6 | Pacific Rim National Park Reserve | 🇨🇦 Canada | |
| 7 | Great Smoky Mountains National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Minneapolis [Saint Paul] | 🇺🇸 United States | |
| 2 | Boston | 🇺🇸 United States | |
| 3 | Chicago | 🇺🇸 United States | |
| 4 | Montreal | 🇨🇦 Canada | |
| 5 | New York City | 🇺🇸 United States | |
| 6 | Detroit | 🇺🇸 United States | |
| 7 | Toronto | 🇨🇦 Canada | |
| 8 | Washington | 🇺🇸 United States | |
| 9 | Vancouver | 🇨🇦 Canada | |
| 10 | Portland | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Narrow-Headed Marsh Fly sighting in Portland on a given day, based on 39 verified sightings from GBIF citizen-science data. It is the 153rd most-seen of the 507 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.
April–May and September
In those months about 10% of wildlife watchers report a Narrow-Headed Marsh Fly in Portland on a given day, against under 5% in June–August and October–March, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Narrow-Headed Marsh Fly sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
10th of 21
Of the 21 cities where we can rate Narrow-Headed Marsh Fly sightings, Portland ranks 10th at under 5%. The best odds are in Minneapolis [Saint Paul] (United States, about 20%), Boston (United States, about 10%) and Chicago (United States, about 10%).
Same family: Syrphidae
The closest relatives of the Narrow-Headed Marsh Fly that you can see in Portland (family Syrphidae, Hover Flies) are Yellow-Haired Sun Fly (about 10%), Narcissus Bulb Fly (about 10%) and Eurasian Drone Fly (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Narrow-Headed Marsh Fly is recorded against all the insects logged in Portland (39 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.
