Aglais milberti

Native through the western and northern United States and up into northern Canada and Alaska in North America (Scott 1986). Habitats are mountains and woods. Host plants are herbaceous, largely restricted to one genus, Urtica (Urticaceae). Eggs are laid on the host plant in clusters usually of several hundred eggs per clutch (as many as 713 have been recorded). Individuals overwinter as adults. There are variable numbers of flights each year depending on latitude; in the far northern part of the range there is one flight in late July, further south there are two flights late June-early Aug. and late August (Scott 1986).

The solid black wing bases edged with bright yellow and orange are unmistakable. Our populations are the nominate subspecies. Recent work by Nylin et al. (2001) shows that Milbert's Tortoiseshell is more appropriately placed in the genus Aglais.

Alaska south to California and New Mexico, east to New England and Newfoundland (Layberry et al. 1998, Opler 1999).

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Alaska east to Newfoundland and south to West Virginia, Oklahoma, Arizona, and California.

Found in many habitats, from prairie coulees to boreal forests and mountain tops.

Comments: A very mobile species that may breed in almost any nettle patch. Most typically in wooded or brushy moist areas often along streams. Adults wander into almost any open or lightly wooded habitats. They usually do not occur in deep forest proper but are seen along forest roads and streams.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

The larvae feed on stinging nettle (Urtica dioica) in British Columbia (Guppy & Shepard 2001) and in Alberta (D. Lawrie, unpubl. data). Unlike other members of the 'hibernator' group, adults of this species are avid flower visitors, but will also visit tree sap or rotting fruit.

Nymphalis milberti Godart: Nymphalidae, Lepidoptera
(observations are from Reed and Graenicher; this butterfly is Milbert's Tortoiseshell)

Asteraceae: Aster ontarionis sn (Re); Salicaceae: Salix discolor [unsp sn] (Gr)

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

10,000 to >1,000,000 individuals

Comments: Abundance fluctuates radically.

Adults feed on flower nectar and sometimes sap. Males perch for females (Scott, 1986).

One, or possibly two generations per year, usually found in early spring and again in late summer.

The conical eggs are green with eight or nine vertical ridges (Guppy & Shepard 2001). Small larvae live communally in silken nests on the hostplant. Mature larvae are solitary, and are black with yellowish subdorsal lines, finely dotted with white, and bear branched spines (Layberry et al. 1998). This tortoiseshell is encountered much more regularly than other tortoiseshells in Alberta, apparently since it does not experience the large fluctuations in number that occur in the California and Compton Tortoiseshells. Adults are strong, rapid fliers but are easily approached when nectaring at flowers. Milbert's, like its other close relatives, overwinters as an adult, emerging early in the spring with faded and often tattered wings. The offspring of the hibernators appear from July onward. Bird et al (1995) state that there are two generations annually, but this needs confirmation; multiple generations in Canada are known only from southeastern Ontario (Layberry et al. 1998).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 3
Specimens with Barcodes: 19
Species With Barcodes: 1

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 2 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Not of concern.

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread, northern "weedy" species.

Degree of Threat: D : Unthreatened throughout its range, communities may be threatened in minor portions of the range or degree of variation falls within natural variation

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed