Icaricia acmon
In 3 days ~20% in a week ~40%
Icaricia acmon, the Acmon blue, is a North American butterfly. It ranges mainly in California and Oregon but can also be seen in southwestern Canada and in the Great Plains Region of the United States, with a total range of about 2,500,000 square km. Because of the breadth of its range, it occurs in several different habitats, such as grasslands, fields, shrub lands, forests, and deserts. Acmon blue was discovered by Pierre Lorquin in 1850, while he visited California during the Gold Rush. It is believed that Acmon Blue was discovered in the San Francisco area.
Wingspan is between the range of 17-30 mm. The tops of the wings are blue with dark edges in males and brown in females. Its underside is white with black spots for both sexes and a red-orange band on the hindwing. Caterpillars are yellow with white hairs and a green stripe down the back. The Acmon is richly colored, more specifically the females with contrasting rows of red lunules (sometimes fused into a band). Meanwhile, the male's hindwing lunules tend to become pink and may disappear during autumn.
Like many other lycaenid butterflies, it has a mutualistic relationship with ants, who protect Acmon blue larvae in exchange for honeydew that the larvae secrete. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Joshua Tree National Park | 🇺🇸 United States | |
| 2 | Yosemite National Park | 🇺🇸 United States | |
| 3 | Sequoia and Kings Canyon National Parks | 🇺🇸 United States | |
| 4 | Channel Islands National Park | 🇺🇸 United States | |
| 5 | Redwood National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Sacramento | 🇺🇸 United States | |
| 2 | San Francisco | 🇺🇸 United States | |
| 3 | Los Angeles | 🇺🇸 United States | |
| 4 | San Diego | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report an Acmon Blue sighting in San Francisco on a given day, based on 523 verified sightings from GBIF citizen-science data. It is the 48th most-seen of the 737 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 40%, if each day is a fresh chance.
May to September
In those months about 10% of wildlife watchers report an Acmon Blue in San Francisco on a given day, against under 5% in October to April, the lowest months. Those are among San Francisco's driest months, with almost no rain against 110 mm in December.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Acmon Blue sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Among the best
Of the 4 cities where we can rate Acmon Blue sightings, San Francisco ranks 2nd at about 10%, level with the leaders once rounded. The best odds are in Sacramento (United States, about 10%).
Same family: Lycaenidae
The closest relatives of the Acmon Blue that you can see in San Francisco (family Lycaenidae, Gossamer-winged Butterflies) are Gray Hairstreak (about 10%), Western Pygmy-Blue (about 10%) and Spring Azure (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Acmon Blue is recorded against all the insects logged in San Francisco (523 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.
