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Butterflies of Mexico, USA & Canada
Silvery Blue
Glaucopsyche lygdamus  EDWARDS, 1881
Family - LYCAENIDAE
subfamily - POLYOMMATINAE
Tribe -
Glaucopsyche lygdamus Massachusetts, USA  Frank Model
Introduction
About 120 members of the cosmopolitan subfamily Polyommatinae are found in the Americas, most of found in the Andes. About 30 species occur in North America - the exact number is uncertain as there is conjecture regarding the taxonomic status of several 'species'.
The genus Glaucopsyche consists of 18 species variously distributed across the temperate regions of the northern hemisphere. There are 3 species in North America: lygdamus, piasus and xerces.
Males of lygdamus are pale shining blue on the upperside, often with a violet tinge. The borders of the wings are narrow and dark brown, fringes with white. In females the blue is usually confined to the basal third of the wings, and there is often a dark vertical bar visible at the end of the forewing discal cell. The underside ground colour is grey in males, and tends more towards greyish-brown in females. The black spots vary considerably in size even within a given subspecies. They are most prominent however in the Nova Scotia race mildredae. In the extinct Californian taxon xerces the black centres to the spots were absent, leaving conspicuous blank white spots in their place.
Glaucopsyche lygdamus is widely distributed across North America, from Quebec and Nova Scotia to Mexico. There are 20 named subspecies.
Habitats
This species can be found in a vast array of habitats including deserts, dunes, marshes, clearings and glades in deciduous or coniferous woodlands, meadows, prairies, grasslands, montane scree slopes, roadsides and just about any other undisturbed habitat where the larval foodplants grow.
Lifecycle
The eggs are laid singly on the flowerbuds or leaves of Astragalus, Hedysarum, Lathyrus, Lupinus, Lotus, Medicago, Oxytropis, Thermopsis, Vicia and other herbaceous Fabaceae. Often several eggs will be laid on the same plant, or even on the same leaflet, by various females or a single returning female. The larvae are tended by ants. They are of the typical Lycaenid shape, and exist in various colour forms according to subspecies, foodplant and habitat. Thus a larva of subspecies incognitus feeding among the purple flowers of Lupinus will have a purplish-brown ground colour, while a larva of australis feeding on Lotus may be greenish-yellow. All varieties have a thin dark dorsal stripe, and have suffused oblique white markings on each segment. The pupa is normally dark brown with greenish wing pads, and also occurs in a blackish form. Pupation takes place on the ground but the pupa is soon covered with debris by ants or transported to their nests.
Adult behaviour

The adults visit a wide variety of plants for nectar, but favour Lotus flowers and other Fabaceae. In late afternoon they move to sheltered areas of ground where they roost in a head-down posture on flowerheads.

 

 

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