Eristalinus aeneus
In 3 days ~10% in a week ~20%
Eristalinus aeneus (Scopoli, 1763), the common lagoon fly, is a fairly common species of syrphid fly observed throughout the United States and Europe. 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 occurs along shorelines in rock pools containing large amounts of decaying seaweed.
For terms see Morphology of Diptera The wing length is 6.5–9.25 mm. The eyes are patterned with obvious black spots. Tergites 2 and 3 are completely shiny. The thoracic dorsum has faint greyish stripes (in Southern Europe it has five strong grey stripes). In males the eyes meet on the frons. In females the eyes are bare on the lower half. The hind tibiae have a black ring after middle, and all tarsi with segments 2–4 darkened.
The male genitalia are figured by Pérez-Bañón et al (2003). The larva is figured by Hartley (1961). The distribution of this species is cosmopolitan. inaturalist map The habitat for this species is freshwater: coastal lagoons, ponds, slow-moving rivers, streams and... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Camargue | 🇫🇷 France | |
| 2 | Acadia National Park | 🇺🇸 United States | |
| 3 | Pacific Rim National Park Reserve | 🇨🇦 Canada | |
| 4 | Wadden Sea National Park | 🇩🇪 Germany |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Kuwait City | 🇰🇼 Kuwait | |
| 2 | Jerusalem | 🇮🇱 Israel | |
| 3 | Algiers | 🇩🇿 Algeria | |
| 4 | Tehran | 🇮🇷 Iran | |
| 5 | San Francisco | 🇺🇸 United States | |
| 6 | Torreón | 🇲🇽 México | |
| 7 | Las Vegas | 🇺🇸 United States | |
| 8 | Vancouver | 🇨🇦 Canada | |
| 9 | Sacramento | 🇺🇸 United States | |
| 10 | Boston | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Common Lagoon Fly sighting in Boston on a given day, based on 25 verified sightings from GBIF citizen-science data. It is the 465th most-seen of the 1200 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
August
In that month about 10% of wildlife watchers report a Common Lagoon Fly in Boston on a given day, against under 5% in September to July, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Common Lagoon 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 16
Of the 16 cities where we can rate Common Lagoon Fly sightings, Boston ranks 10th at under 5%. The best odds are in Kuwait City (Kuwait, about 30%), Jerusalem (Israel, about 20%) and Algiers (Algeria, about 10%).
Same family: Syrphidae
The closest relatives of the Common Lagoon Fly that you can see in Boston (family Syrphidae, Hover Flies) are Margined Calligrapher (about 20%), Eastern Calligrapher (about 20%) and Transverse-Banded Flower Fly (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Common Lagoon Fly is recorded against all the insects logged in Boston (25 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.
