Narrow-headed Ants Formica exsecta

Field Paintings

This summer I have been fortunate to be able to spend many hours studying one of Britain’s rarest invertebrates, the narrow-headed ant Formica exsecta. This ant is now known from a single site in England and several sites in the Scottish Highlands. It is currently the subject of a Back from the Brink project which is hoping to return the ant to some of its former sites.

I have been helping monitor the ants at its last remaining location in England on the Devon Wildlife Trust reserve at Chudleigh Knighton Heath. We have found over 170 nests and are still learning much about its ecology.

The ecology of this ant is very interesting. The winged male and female ants mating flight occurs in July or August. After mating the female returns to the ground and loses her wings. She then searches out the nest of a close relative the black ant Formica fusca, enters the nest and presumably kills the host queen. She then uses the workers to raise a brood of her own young. Over time the nest becomes a pure narrow-headed ant nest. Other nests are formed by budding off from existing nests and here the newly emerged queens may well return to their natal nest but the detail of this is still unknown.

Like other ants the narrow-headed ants hunt for small insects and also farm aphids for honeydew. On the heath they are often seen on small birch saplings near their nests farming the aphids watch a video of this here.

John Walters

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