 Worker ants are usually the same size as each other , although this is not true for some species ; worker ants of M. brevinoda , for example , vary in length from 13 to 37 millimetres ( 0 @.@ 51 to 1 @.@ 46 in ) . The mandibles of the workers are long with a number of teeth , and the clypeus is short . The antennae consist of 12 segments and the eyes are large and convex . Based on a study on the antennal sensory of M. pyriformis , the antennal sensilla is known to have eight types of sensilla . Large ocelli is always present . 
