 Myrmecia ants are easily noticeable, due to their large mandibles, and large compound eyes that provide excellent vision, and a powerful sting that they use to kill prey. Each of their eyes contains 3,000 facets, making them the second largest in the ant world. Size varies widely, ranging from 8 to 40 millimetres (0.31 to 1.57 in) in length. The largest Myrmecia species is M. brevinoda, with workers measuring 37 millimetres (1.5 in); M. brevinoda workers are also the largest in the world. Almost all species are monomorphic, but M. brevinoda is the only known species where polymorphism exists. It is well known that two worker sub-castes exist, but this does not distinguish them as two different polymorphic forms. This may be due to the lack of food during winter and the fact they could be incipient colonies. The division of labour is based on the size of ant, rather than its age, with the larger workers foraging for food or keeping guard outside the nest while the smaller workers tend to the brood.
