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Ants, insects & climate change

Pete Wilton

Scientists who saved the Large Blue butterfly are now turning their attention to some of the other 10,000 insect species that depend on ants for their survival.

Like the Large Blue these insects – ranging from butterflies and moths to beetles and hoverflies – all rely on ants in one way or another for food and protection and are known to be particularly vulnerable to the sort of environmental changes associated with climate change.

'Only seven or eight of the 10,000 or so insect species that we know depend on ants have been studied at all,' Jeremy Thomas of Oxford University’s Department of Zoology told us.

'Whilst the work done at Oxford and elsewhere on the Large Blue and its relationship with ants saved one species there are thousands more that are living on the edge and, if we don’t act quickly, could disappear from Britain’s meadows, woods and heathland.'

The insects in question range from beautiful butterflies such as the Silver Studded Blue [Plebejus argus], which co-habits with the Black garden ant [Lasius niger], to a hoverfly you might mistake for a bee [Microdon mutabilis], which lives off a type of wood ant [Formica lemani], to a beetle [Lomechusa] which specialises in getting ants to feed and protect it.

It's amazing to think that so many insects have found a way to infiltrate ant society and get a 'free ride' from their more socially-inclined neighbours. The nest parasite Lomechusa is a fascinating beast with a cuckoo-like lifestyle, the difference being this beetle never grows up and continues to trick ants into caring for it even as an adult.

But it's this relationship with ants that makes these insects particularly sensitive to small changes in habitat which, whilst not affecting them directly, can have a devastating impact if they affect the ant populations they depend on.

Jeremy explains: 'In the case of the Large Blue butterfly and the red ants [Myrmica sabuleti] it was a combination of less grazing by both human livestock and wild animals that caused the ants' 'microhabitat' to become overgrown, so that ant populations fell and there weren’t enough ants to nurture the next generation of Large Blues.'

'The worry is that these are just the sort of changes we can expect to see as a result of climate change.'

The researchers intend to study the impact human activity is having on 11 endangered insect species and the ants that support them. They will then use this information to predict how future changes in climate and land use will affect these populations and work out what can be done to mitigate any harmful effects.

Jeremy adds: 'our previous work has shown that if we can understand the complex relationships between these species and what they need to survive then we can take action to save them.'

'When you think that the number of insect species that rely on ants is twice the number of all mammal species in the world then it seems if we are serious about preserving biodiversity then we need to do all we can to save such endangered insects.'

Professor Jeremy Thomas is based at Oxford's Department of Zoology.