Formica cunicularia is a mining ant

Ant

Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...

 of the Formica fusca group. Forelian

Auguste-Henri Forel

Auguste-Henri Forel was a Swiss myrmecologist, neuroanatomist and psychiatrist, notable for his investigations into the structure of the human brain and that of ants. For example, he is considered a co-founder of the neuron theory...

 systematics places it in the subgenus

Subgenus

In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...

 Serviformica. Locally common in southern England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, its appearance and habits ally it, to some extent, with Formica rufibarbis

Formica rufibarbis

Formica rufibarbis is a European formicine ant of the Formica fusca group. In the classification by Auguste Forel, it is treated in the subgenus Serviformica....

, although the former's red markings are far less conspicuous. Horace Donisthorpe

Horace Donisthorpe

Horace St. John Kelly Donisthorpe was an eccentric British myrmecologist and coleopterist, memorable in part for his enthusiastic championing of the renaming of the genus Lasius after him as Donisthorpea, and for his many claims of discovering new species of beetles and ants.He is often considered...

 comments:

Forel points out that [Formica fusca var.] rubescens [=F. cunicularia] has frequently been confounded with rufibarbis, and it is probable that some British records of [...] rufibarbis really refer to this variety.

F. cunicularia, unlike most other Formica

Formica

Formica is a genus of ants of the family Formicidae, commonly known as wood ants, mound ants, or field ants. Formica is the type genus of the Formicidae, and of the subfamily Formicinae...

 fusca-group species, can form noticeable hillocks over its nests, and in addition to these produces rufibarbis-like runs in the vicinity of its nest.
Donisthorpe states that:

In the New Forest

New Forest

The New Forest is an area of southern England which includes the largest remaining tracts of unenclosed pasture land, heathland and forest in the heavily-populated south east of England. It covers south-west Hampshire and extends into south-east Wiltshire....

 it occurs in earth-mounds, at Seaton

Seaton, Devon

Seaton is a seaside town in East Devon on the south coast of England. It faces onto Lyme Bay, to the west of the mouth of the River Axe with red cliffs to one side and white cliffs on the other. Axmouth and Beer are nearby...

 under stones, in the Landslip, Isle of Wight

Isle of Wight

The Isle of Wight is a county and the largest island of England, located in the English Channel, on average about 2–4 miles off the south coast of the county of Hampshire, separated from the mainland by a strait called the Solent...

, in the side of the cliff, and at Fairlight

Fairlight, East Sussex

Fairlight is a village in East Sussex, England within Rother district, three miles to the east of Hastings. Fairlight is also the name of the civil parish forming part of the Rother district which includes the villages of Fairlight and Fairlight Cove.The village of Fairlight lies on a minor road...

 I found it in the side of the cliff and in earth-mounds in the undercliff - one of the nests being traced by tracking a worker which was carrying home a fly in its jaws.

Donisthorpe records the species as having occurred as far north as Bewdley

Bewdley

Bewdley is a town and civil parish in the Wyre Forest District of Worcestershire, England, along the Severn Valley a few miles to the west of Kidderminster...

 in Worcestershire

Worcestershire

Worcestershire is a non-metropolitan county, established in antiquity, located in the West Midlands region of England. For Eurostat purposes it is a NUTS 3 region and is one of three counties that comprise the "Herefordshire, Worcestershire and Warwickshire" NUTS 2 region...

.