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Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.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
 
Brown Argus
Aricia agestis DENIS & SCHIFFERMÜLLER, 1775
Family - LYCAENIDAE
subfamily - POLYOMMATINAE
 
 introduction | habitats | lifecycle | adult behaviour
 
Brown Argus Aricia agestis, female nectaring at germander speedwell, Dorset, England
 
Brown Argus Aricia agestis, male, Ballard Down, Dorset, England
 
Introduction
 

The Brown Argus is a widespread and fairly common species found throughout Europe with the exception of Scandinavia, Ireland and northern Britain. It also occurs in north Africa, the Middle East, and across temperate Asia as far east as Siberia and Amur.

 

Across most of it's range it is double-brooded, emerging in May and August, but in the Mediterranean region there are usually 3 broods, in April, July and October.

 

In northern England, Scotland, Scandinavia, and the high alpine regions of Europe it is replaced by the Northern Brown Argus ( = Mountain Argus ) Aricia artaxerxes, which differs from the Brown Argus in being single brooded. There is much variation between the various races of artaxerxes, the Scottish form for example having a white discal spot on the upperside forewing, and greatly reduced black spots on the underside. The subspecies allous however, which is found in the Alps and Pyrenees, is virtually identical to agestis on the underside, but has reduced orange lunules on the upperside.

 

In Britain novice lepidopterists often confuse this species with the female Common Blue, but the latter always has a trace of blue scaling on the upperside wings. The Brown Argus often has a bluish or greenish sheen, but never any blue scales.

Additionally the Brown Argus ( right ) has a pair of white-ringed black spots arranged like a colon ( : ), near the costa of the underside hindwing, compared with the single spot found in this position on the Common Blue.

The underside markings can also be used to distinguish the Brown Argus from the females of the many other "blues" and "arguses" in Europe, each of which has a slightly different configuration of spots.
  

 

Habitats
 
In England the Brown Argus breeds mainly on calcareous ( limestone / chalk ) grassland, where the caterpillar's foodplant common rockrose grows amongst fine grasses. Many sites are on south facing slopes, often heavily grazed by rabbits, and characterised by an abundance of ant-hills on which the foodplants grow.
 
Around the coast of Britain there are colonies on cliff tops, and on the calcareous dunes of Wales, Cornwall, Norfolk, Suffolk, Essex and Kent.
 
Away from calcareous habitats the butterfly is much scarcer, but is sometimes found in odd habitats, e.g. a friend photographed a fresh female seen along a track through a Surrey woodland on clay in late July 2008.
 
Lifecycle
 
Males of the first brood begin to emerge in early May, and females about a week later. They have a lifespan of about 2 weeks.
 
The disc-shaped dull whitish eggs are laid singly on the underside of leaves of common rockrose Helianthemum chamaecistus, usually close to the stem. Other foodplants used less frequently include common storksbill Erodium cicutarium and dove's foot cranesbill Geranium molle. They hatch after about 7 days.
 
When young the caterpillar nibbles at the underside of the leaves, leaving a distinctive pattern of tiny holes which are visible from above. Older larvae feed on the upperside of the leaves, and are attended by ants ( Lasius niger, L. alienus, L. flavus and Myrmica sabuleti ) which "milk" them for a sugary secretion. They feed by day.
 
The fully grown caterpillar is plump and green, with a purple stripe below the spiracles, and another on the back.
 
The chrysalis is formed in July on the ground, and is also attended by ants, which bury it just below the surface. It is dull olive in colour, marked with a pinkish lateral line.
 
The second generation of adults emerges in late July and early August. The caterpillars resulting from this brood go into hibernation when quite small, usually in the 3rd instar, and re-awaken in February or March of the following year. They develop quickly, becoming fully grown and ready to pupate by the end of March.
 
Aricia agestis, male in typical perching posture
 
Adult behaviour
 
Brown Argus males tend to congregate in sheltered areas along dykes or at the bottom of south facing hills. They do not have fixed territories, but perch in various positions on grasses and flowers, and fly up instantly to investigate every passing insect. They are not the cleverest of butterflies, and seem unable to differentiate visually between flies, Skippers, Blues and Fritillaries.
 
They also seem unable, from more than a few centimetres away, to recognise butterflies with which they have already had sorties, and will e.g. intercept the same individual Common Blue or Marsh Fritillary numerous times if it crosses their path again. However, during these inter-species aerial encounters they make very close contact, and almost certainly "exchange names" via pheromone detection. At this point they recognise that the intruder is not of their own species, and break off the encounter.
 
Females that have already mated are chased by males until they settle. They then close their wings and remain motionless in an attempt to escape detection. This ploy rarely works however and the males usually locate them and attempt to copulate, but quickly give up and fly off if the female is unwilling.
 
When virgin females are intercepted, copulation takes place almost immediately, without any prenuptial ritual. Once copulated the butterflies are extremely reluctant to move from the grass blades on which they settle.
 
After mating the females roam randomly, searching for spots where the larval foodplants grow in warm and sheltered positions. At many sites, e.g. Martin Down in Hampshire, and Levin Down in West Sussex, the females seek rockrose plants that are growing on ant-hills, and it is possible that they are genetically programmed to recognise the chemical odours produced by the ants.
 
Brown Argus Aricia agestis, female nectaring at horseshoe vetch, Dorset, England
 
Adults of both sexes nectar at a wide variety of low growing flowers, the first brood favouring daisy, buttercup, bird's foot trefoil, horseshoe vetch, common vetch, milkwort, dandelion and rockrose. Summer brood adults tend to congregate to nectar at clumps of marjoram at the base of hills.
 
In late afternoon the butterflies roost communally on grass-heads, usually with the males and females forming separate groups. The roosting sites are often on the top of banks, where the adults are exposed to the last rays of the setting sun.
 
Brown Argus Aricia agestis, female at roost on grass head, Broughton Down, Hampshire, England
 
                                                       
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 images protected by Copyright © Adrian Hoskins 2007-2008, ( unless stated otherwise ) 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.
 
Website designed, produced and owned by Adrian Hoskins