The Southern Wood Ant (Formica rufa) is a species of ant in the Formicidae family.
This species, also known as the Horse Ant, is widespread in most of Europe, but found only in the south in Britain, though they are often common. Workers range from 8-10mm in length, and are red with black abdomen. When disturbed, they will squirt a formic acid as a defence, from their abdomen. These species build large mounds out of conifir needles, and will catch many invertebrates from nearby and bring them back.
Southern Wood Ant - http://www.flickr.com/photos/qwertyqwertyqwerty/