the type species of Myrmecia in 1840. Genetics The number of chromosomes per individual varies from one to over 70 among the species in the genus. The genome of M. pilosula is contained on a single pair of chromosomes (males have just one chromosome, as they are haploid). This is the lowest number possible for any animal, and workers of this species are homologous. Like M. pilosula, M. croslandi also contains a single chromosome. While these ants only have a single chromosome, M. pyriformis contains 41 chromosomes, while M. brevinoda contains 42. The chromosome count for M. piliventris and M. fulvipes is two and 12, respectively. The genus Myrmecia retains many traits that are considered basal for all ants (i.e. workers foraging alone and relying on visual cues). Species groups Myrmecia contains a total of nine species groups. Originally, seven species groups were established in 1911, but this was raised to 13 in 1951; Promyrmecia had a total of eight, while Myrmecia only had five. M. maxima does not appear to be in a species group, as no type specimen is available. Description Myrmecia ants are easily noticeable due to their large mandibles, 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 in length. The largest Myrmecia species is M. brevinoda, with workers measuring ; 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 subcastes exist, but this does not distinguish them as two different polymorphic forms. This may be due to the lack of food during winter and 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. Their coloration is variable; black combined with red and yellow is a common pattern, and many species have golden-colored pubescence (hair). Many other species are brightly colored which warns predators to avoid them. The formicine ant Camponotus bendigensis is similar in appearance to M. fulvipes, and data suggest C. bengdigensis is a batesian mimic of M. fulvipes.