Milbert's Tortoiseshell (Aglais milberti) is in the Brush-footed Butterflies family (Nymphalidae). Across the U.S., iNaturalist users have logged 5,342 research-grade observations of it in our sample, peaking in July.
Seasonal pattern in the national data: summer visitor / breeder. Counts also reflect when people are out photographing, so compare months within a state rather than across states.
When to photograph Milbert's Tortoiseshell: observations by month (U.S.)
About Milbert's Tortoiseshell
Aglais milberti, the fire-rim tortoiseshell or Milbert's tortoiseshell, is the only species of Aglais that occurs in North America.From Wikipedia via iNaturalist — article, CC BY-SA.
Milbert's Tortoiseshell by state
| State | Observations | Peak month | Main season |
|---|---|---|---|
| Colorado | 606 | July | Jun–Aug |
| Alaska | 498 | May | Apr–Aug |
| Wyoming | 411 | July | Jun–Aug |
| Vermont | 410 | July | Jun–Oct |
| Montana | 408 | July | Jun–Sep |
| Washington | 405 | July | May–Aug |
| California | 335 | July | Jun–Aug |
| Idaho | 333 | June | Mar–Aug |
| New Mexico | 292 | July | Jun–Aug |
| Utah | 277 | July | Jun–Aug |
| Oregon | 235 | July | May–Aug |
| Ohio | 231 | September | Jun–Oct |
| Minnesota | 176 | July | Jun–Aug |
| New York | 151 | July | Jun–Aug |
| Nevada | 109 | June | May–Aug |
| Arizona | 94 | July | Jun–Aug |
| New Hampshire | 82 | August | Jul–Oct |
| Maine | 49 | August | Jun–Oct |
| South Dakota | 46 | June | Jun–Jul |
| Nebraska | 44 | June | Jun–Jun |
| Pennsylvania | 39 | July | May–Oct |
| Wisconsin | 37 | July | Jul–Jul |
| Michigan | 35 | July | May–Sep |
| Massachusetts | 19 | June | Jun–Jul |
| North Dakota | 12 | April | Apr–Jun |
Main season = months with at least 30% of the state's peak-month count.
Related butterflies (Brush-footed Butterflies)
Monarch
Gulf Fritillary
Common Buckeye
Red Admiral
Pearl Crescent
Painted Lady
American Lady
Variegated Fritillary
Photography tips
- Butterflies are sluggish on cool mornings — the best time for close approaches.
- Keep the sensor parallel to the wings for edge-to-edge sharpness.
- Nectar plants in bloom are reliable places to wait.
FAQ
When is the best time to photograph Milbert's Tortoiseshell?
Nationally, July has the most observations, with the main season from May to September.
Where is Milbert's Tortoiseshell most often seen?
The most observations come from Colorado, Alaska, Wyoming.