Narrow headed ant  (Formica exsecta)

The workers of this endangered ant can be distinguished from other wood ants by the characteristic deep notch on the back of the head (2). It is a medium-sized ant, red and dark brown in colour, and is aggressive (4). The wood ants are the largest of the British ants, all of which are reddish in colour and have a single segment forming the 'waist' (2). Reproductive females (queens) and males are larger than the workers, and have well-developed thoraxes and wings (which are shed from the body after mating). Males have obvious sex organs that protrude from the abdomen (2).