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Exploiting Myrmecophily, Blue Butterflies Fool Ants

Entomologists are finally unraveling the extraordinary relationship between certain ants and two very rare British insects -- the large blue butterfly and the Microdon hoverfly.

As well as offering fascinating insights into how insect species co-evolve, the findings - which will be reported by Dr. Jeremy Thomas to a meeting of the Royal Entomological Society tomorrow - provide the key that will allow conservationists to reintroduce insect species such as the large blue butterfly that had become extinct in Britain.

As many as 100,000 insect species interact with ants, a phenomenon known as myrmecophily. The vast majority of these are happy relationships -- either a simple and peaceful coexistence or a mutually beneficial relationship in which both the ant and the other insect species gain something from each other.

But a small number of very rare insects, including the large blue butterfly, have abandoned such cozy relationships.

According to Dr. Thomas of the Centre for Ecology and Hydrology, "About 10% of myrmecophiles have evolved a much more one-sided relationship, in which they infiltrate ant societies and exploit the resources of the colony. They have turned into insect versions of the cuckoo. It is an extraordinary and extreme adaptation to get access to a plentiful supply of food and protection."

Entomologists believe that at an earlier stage in its evolution, the large blue butterfly probably brought something to its relationship with the ant, and Dr. Thomas's work has revealed two very different strategies used by the butterfly to exploit the ants.

"Large blue butterflies were probably mutualists in the past, but having sneaked into ant societies they then attack the ants or take their food," he says.

Larvae of Maculinea arion -- the species of large blue butterfly that was a British native -- eat the developing ants within the nest, while another species, M. rebeli, is fed by worker ants within the colony as if it were a young ant.

M. rebeli, and probably M. arion, fool the ants into believing they are one of their own by mimicking the complex cocktail of 30-40 chemicals that ants use to communicate with one another.

The large blue M. arion became extinct in Britain in 1979 after early attempts to conserve it failed. According to Dr. Thomas: "No one knew why the early attempts at conserving the large blue in Britain failed. We know now that conservationists took the wrong measures because they misunderstood its relationship with ants."

As a result of this new knowledge of its life cycle, at least six populations of the butterfly have been successfully re-established in three regions of southwest England.

Dr. Thomas will also tell the meeting about his work with Microdon hoverflies, whose biology is much less well understood, but which has major implications for the species' conservation in the UK.

Founded in 1833 as the Entomological Society of London, the Royal Entomological Society plays a major national and international role in disseminating information about insects and improving communication between entomologists. It has over 1,500 members in the UK and abroad.

[Contact: Dr. Jeremy Thomas, Becky Allen]






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