Butterflies of the World - Lifecycle, Ecology, Taxonomy, Conservation, Photography, Butterfly Holidays, Photo Galleries, Book Reviews and more.........
Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.
Butterflies of Britain & Europe
 
Silver-studded Blue
Plebejus argus LINNAEUS, 1758
Family - LYCAENIDAE
subfamily - POLYOMMATINAE
 
 introduction | habitats | lifecycle | adult behaviour
 
Silver-studded Blue Plebejus argus, male, Hawkhill, New Forest, Hampshire, England
 
Introduction
 
The Silver-studded Blue is widely distributed throughout Europe, but absent from central Spain, southern Portugal, Scotland, Ireland and northern Scandinavia. Beyond Europe it's range extends across temperate Asia to northern China and Japan.
 
In Britain it cannot be confused with any other species, but elsewhere within it's range it can very easily be mistaken for the Idas Blue Plebejus idas. The 2 species can only reliably be distinguished by examining the tibia on the foreleg of the male - in argus this is spined, in idas it is not.
 
Other closely related and very similar species occurring in Europe include Reverdin's Blue Plebejus argyrognomon, and the Zephyr Blue P. pylaon.
 

 Silver-studded Blue Plebejus argus, male, Prees Heath, Shropshire, England

 
Habitats
 
Unlike other British blues, this is a heathland butterfly. It is a very localised species, but in suitable habitats the populations are often very large, comprising of hundreds or even thousands of butterflies. It breeds chiefly on humid heaths in Hampshire, Dorset and Surrey, favouring sheltered areas that have regenerated following burning, clearing, or heavy cattle grazing.
 
Colonies also exist on coastal dunes in Cornwall, south Devon and the Gower peninsula of south Wales. Populations which once existed on chalk grasslands have all become extinct, but there are still large populations on limestone cliffs at Great Ormes Head in north Wales, and small populations in limestone quarries at Portland, Dorset.
 
Silver-studded Blue Plebejus argus, male, Iping Common, West Sussex, England
 
Lifecycle
 
In warmer parts of Europe the butterfly is double brooded, emerging in May and August, but in Britain there is only a single generation, which emerges in late June.
 
At heathland sites the eggs are laid singly in July at the base of young shoots of cross-leaved heath Erica tetralix, heather Calluna vulgaris, bell heather Erica cinerea or gorse Ulex europaeus.
 
On limestone sites they are laid on the stems of bird's foot trefoil Lotus corniculatus or rockrose Helianthemum chamaecistus, very close to the base of the plants.
 
In both situations they are always laid in proximity to nests of the black ant Lasius niger.
 
The tiny larva develops within the egg in the late summer, but does not hatch until the following March. It feeds by day on the flowers and tender leaf tips of the foodplants, and is constantly attended by ants. The ants milk "honey" that the caterpillar produces from an eversible gland. In return for their meal they protect the larva from wasps, spiders and carnivorous bugs.
 
When ready to pupate, the larva is driven or carried into the ant's nests. The pupa is attended by the ants until the butterfly is ready to emerge in late June or early July, at which time it crawls out of the nest and makes it's way up a stem where it settles to expand and dry it's wings.
 
The butterfly / ant relationship appears to be a true example of symbiosis, as captive larvae which are prevented from having contact with ants invariably die.
 
Silver-studded Blue Plebejus argus, male, Ocknell, New Forest, Hampshire, England
 
Adult behaviour
 

The steely blue males are easily seen, flying low over heather or grasses, and stopping occasionally to nectar at bell heather, bird's foot trefoil or rockrose. Females are much harder to see, as they are far more sedentary and duller in colour, being earthy brown with an indistinct series of orange sub-marginal lunules.

 

Plebejus argus, male at roost on cross-leaved heath, Shropshire, England

 

Overnight or in overcast weather conditions the butterflies roost on cross-leaved heath, heather, or less commonly amongst grasses or on bushes. On sunny days the butterflies are active until sunset, and at certain sites can sometimes be found basking in groups of 30 or 40, congregating on bushes or heather clumps to soak up the last remnants of sunlight before going to roost or the night.

 
                                                       
Almost every British and European species of butterfly is declining rapidly in numbers, due in most cases to loss or degradation of habitats.
 
You can help to reverse the decline by supporting conservation organisations which purchase and manage habitats as nature reserves, and which lobby government at local, national and international levels, often very successfully, to bring about changes in farming, forestry and urban development policies.
 
Please contact the conservation organisations for advice on how you can help protect British and European butterflies and their habitats. You may be able to offer practical help e.g. by monitoring butterfly populations or helping to manage nature reserves. Donations to these organisations enable them to employ ecologists and biologists. Even if you are unable to provide such help, merely having your name on the membership list can be a powerful tool for conservation organisations wishing to demonstrate the levels of support they have for their policies.

 

 
Text and photographs protected by Copyright © Adrian Hoskins 2007-2008, and must not be reproduced or published in part or in whole elsewhere in any form without written permission from Adrian Hoskins. Breach of copyright will be pursued by litigation.
 
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