Butterflies of Mexico, USA & Canada
Milbert's Tortoiseshell
Aglais milberti  FABRICIUS, 1798
subfamily - NYMPHALINAE
Aglais milberti, Massachusetts, USA  Frank Model
The genus Aglais is considered by some workers to be a subgenus of Nymphalis. It comprises of 6 species, found variously in North America, Europe and temperate Asia. The butterflies are similar in colour and pattern to certain Nymphalis species e.g. xanthomelas, but are more richly coloured and significantly smaller in wingspan. There is only one Aglais species found in North America - milberti.
Aglais milberti is distributed from Newfoundland to Arizona. There are 4 named subspecies - viola which is found in New Brunswick and Newfoundland in Canada; milberti from Pennsylvania, Indiana, New Hampshire, Massachusetts, Wisconsin; subpallida from California, Colorado, Nevada, Oregon, Washington, South Dakota and Wyoming; and pullum from Arizona.
This species is found in open temperate habitats including meadows, farmland, woodland clearings and glades, riverbanks, wasteland, wild gardens and almost anywhere else where the caterpillar's foodplants grow. It can be found at altitudes between sea level and at least 1500m.
The pale green vertically ribbed eggs are laid either singly or in loose piles of up to half a dozen, on the underside of leaves of stinging nettles Urtica ( Urticaceae ). The larvae live gregariously in silk tents spun on the upper leaves of nettle plants, and construct a new tent after each moult. After the final moult that disperse and feed solitarily. When fully grown they are black, covered in white dots. They have a pair of thin yellow lines along the back and a broken yellow stripe below the spiracles. The back is adorned with multi-branched black spines and there is a series of yellowish spines along the sides. The pupa is formed hanging by the cremaster from a stem of the foodplant or from a nearby woody stem.
Adult behaviour
Males perch, with wings either open or closed, on the foliage of low growing plants, where they wait to intercept passing females. The courtship ritual is very protracted, beginning in mid afternoon and continuing until dusk. It involves a great deal of tactile stimuli, as the male drums on the hindwings of the female with his antennae, walks over her wings, and chases her from place to place until the pair settle beneath a bush to copulate at dusk. They remain in copula until the following dawn.
Both sexes nectar avidly at flowers of many species. Males imbibe mineralised moisture from damp ground, and pass the minerals to the females during copulation.


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