The plain is an important stronghold for declining downland butterflies. A high concentration of colonies of three nationally scarce species, the Adonis blue (Polyommatus bellargus), Duke of Burgundy (Hamearis lucina), and the largest population of marsh fritillary (Euphydryas aurinia) on the chalk, occur. A colony of brown hairstreak (Thecla betulae) is present on East Salisbury Plain at one of its two Wiltshire localities. Strong populations of other downland species such as chalkhill blue (Polyommatus coridon) and dark green fritillary (Argynnis aglaja) are found, and of note here is the occurrence of grayling (Hipparchia semele), a butterfly rarely found away from the coast.