
Narrow-headed Ants (Formica exsecta) feeding on a moth wing. South Devon, UK. May. From https://www.flickr.com/photos/160919311@N04/46167270472
Dear Readers, the insect in the photo is a Narrow-headed Ant (Formica exsecta). It is one of the rarest ants in the UK, with populations in Scotland, and a single isolated population in Devon. The ant lives in woodland, where it has a symbiotic relationship with plants such as the Small Cow Wheat (Melampyrum sylvaticum), whose seeds are dispersed by the insect. The Capercaillie also uses the ants as a food source.

Small Cow-wheat (Photo By Konrad Lackerbeck, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=2278812)
These wood ants like more open areas in woodland, and build nests about 25cm tall around tussocks of grass or other vegetation – as the plants rot, they provide heat to the nest. The south-facing side is usually largest, which means that it is literally ‘solar-heated’. The individual workers also sunbathe, returning to the eggs and young and providing them with additional heat from their bodies. Finally, the roof of the nest is ‘thatched’, providing another layer of insulation.
A queen Narrow-headed Ant can live for 25 years, and there can be up to five thousand workers. The nest is also shared with another specieIs of ant, the Shining Guest Ant (Formicoxenus nitidulus) which is only 2-3mm long – it benefits from the protection of the nest, but may also solicit food from returning Narrow-headed Ant workers. There can be several Shining Guest Ant nests in each Narrow-headed Ant nest.
It’s evident that the Narrow-headed Ant is an important part of its ecosystem, but it is also vanishingly rare. The Devon population is the last one in England, and the species as a whole is described as ‘Near Threatened’ on the IUCN Red List. All this makes what’s happened in the last few days even worse.
Someone appears to have gone into the Chudleigh Knighton Heath reserve in Devon, where the ants live, and dug up an entire nest with a spade.
There are apparently such people as ‘ant collectors’, who would pay a high price for such a rare species. Another possibility is that the nest has been taken by someone keen on re-wilding, who wants to introduce the ants elsewhere. Both possibilities pose risk to the ants, who were being monitored closely by the Devon Wildlife Trust and Buglife – moving a nest, even to other suitable habitat, is a complicated procedure, involving a lot of assessment as to whether the spot provides enough shelter and food for the ants. Whatever the reason, decades of work by conservationists has been disrupted, and we can only hope that the ants survive. This is a crime and has been reported to Devon and Cornwall police, so let’s hope that someone shops the perpetrator.
I knew that people would steal nestlings and bird eggs, rare fungi and orchids, but this is the first time I’ve heard of anyone stealing an ants’ nest. Let’s hope it’s the last.














































