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Silver-studded blue Plebejus argus The silver-studded blue butterfly is the rarest of all the butterflies you can see on the Suffolk Sandlings. It is now confined to a few heathland sites in the Sandlings area, having once been widespread both here and in the Brecks.
Silver-studded blues and black ants Silver-studded blues require the presence of two species of black ant which tend the butterfly larvae, protecting them from parasites, in return for a sugary secretion. Females lay their eggs on bell heather and ling. The eggs remain there over winter and hatch as caterpillars in March or April to feed on the heather. The caterpillars secrete a sweet sticky substance which the black ants crave. To ensure they have a plentiful supply, the ants transport the caterpillars into their nest to protect them from predators - and only bring them out to feed. When the caterpillars turn into a chrysalis in June they remain in the ants' nest for about 18 days, before emerging - still covered in black ants! Spotting silver-studded blues Adults are on the wing in late June, July and early August. The colonies at Minsmere, Dunwich and Martlesham are the best places to see them. Look out for males defending patches of heather from other males, so as to attract females to feed on the nectar of the heather flowers. |
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Like so many other heathland species, the survival of the silver-studded blue goes hand in hand with the survival of the heaths and its decline has followed that of its heathland habitat. Habitat management for the silver-studded blue involves maintaining and creating bare soil and short vegetation with a high proportion of bell heather, the favoured food plant of larvae and adults, to produce a warm microclimate for the ants and larvae.