Nothomyrmecia

Nothomyrmecia is a medium-sized ant measuring in length. Workers are monomorphic, meaning that there is little morphological differentiation among one another. The mandibles are shorter than the head. They have 10 to 15 intermeshing teeth and are less specialised than those of Myrmecia and Prionomyrmex, being elongate and triangular. The head is longer than it is wide and broader towards the back. The sides of the head are convex around the eyes. The long antennal scapes (the base of the antenna) extend beyond the occipital border, and the second segment of the funiculus (a series of segments between the base and club) is slightly longer than the first, third and fourth segment. The node, pronotum, epinotum and thorax are longer than broad, and the mesonotum is just as long as it is wide. The first segment of the gaster (the bulbous posterior portion of the metasoma) is broader than long by a third and broader at the back than the front with strongly convex sides. A long and retractable stinger is present at the rear of the abdomen. It has been described as "prominent and effective" and is capable of inflicting a painful sting to humans. Despite its many plesiomorphic features, the sting apparatus of Nothomyrmecia is considered less primitive than those found in other ants such as Stigmatomma pallipes. It is the only known species of ant that contains both a sting and a 'waist' (i.e. it has no postpetiole between the first and second gastral segments). The cocoons have thin walls and produce meconium (a metabolic waste product expelled through the anal opening after an insect emerges from its pupal stage). In general, the body structure of all Nothomyrmecia castes demonstrates the primitive nature of the species. Notable derived features include vestigial ocelli on workers, brachypterous queens, and the mesoscutal structure on males. The morphology of the abdomen, mandibles, gonoforceps (a sclerite, serving as the base of the ovipositors sheath) and basal hamuli show it is more primitive than Myrmecia. The structure of the abdominal region can separate it from other Myrmeciinae relatives (the fourth abdominal segment of Myrmecia is tubulate, whereas Nothomyrmecia has a non-tubulated abdominal segment). The appearance of the fourth abdominal segment is consistent with almost all aculeate insects, and possibly Sphecomyrma. The feature of non-functional, vestigial wings may have evolved in this species relatively recently, as wings might otherwise have long-since disappeared completely had they no function for dispersal. Wing-reduction could somehow relate to population structure or some other specialised ecological pressure. Equally, wing-reduction might be a feature that only forms in drought-stressed colonies, as has been observed in several Monomorium ant species found throughout semi-arid regions of Australia. As yet, scientists do not fully understand how the feature of non-functional, vestigial wings arose in Nothomyrmecia macrops. ==Taxonomy==

Discovery The first collection of Nothomyrmecia was made in December 1931 by amateur entomologist, Amy Crocker, whose colleagues had collected a range of insect samples for her during a field excursion, including specimens of two worker ants, reportedly near the Russell Range, inland from Israelite Bay in Western Australia. Crocker then passed the ants to Australian entomologist John S. Clark. Recognised shortly afterwards as a new species, these specimens became the syntypes. In 2012, a report discussing the possible presence of Nothomyrmecia in Western Australia did not confirm any sighting of the ant between Balladonia and the Western Australian coastal regions. After 46 years of searching for it, entomologists have dubbed the ant the 'Holy Grail' of myrmecology. Naming In 1934 entomologist John S. Clark published a formal description of Nothomyrmecia macrops as a new species and within a completely new genus and tribe (Nothomyrmecii) of the Ponerinae. This proposal was rejected by American entomologist William Brown Jr., who placed it in the subfamily Myrmeciinae with Myrmecia and Prionomyrmex, under the tribe Nothomyrmeciini. Its distant relationship with extant ants was confirmed after its rediscovery, and its placement within the Formicidae was accepted by most scientists until the late 1980s. The single waist node led scientists to believe that Nothomyrmecia should be separate from Myrmecia and retained Clark's original proposal. This proposal would place the ant into its own subfamily, despite many familiar morphological characteristics between the two genera. This separation from Myrmecia was retained until 2000. In 2003, Russian palaeoentomologists G. M. Dlussky and E. B. Perfilieva separated Nothomyrmecia from Prionomyrmex on the basis of the fusion of an abdominal segment. In the same year, American entomologists P. S. Ward and S. G. Brady reached the same conclusion as Dlussky and Perfilieva and provided strong support for the monophyly of Prionomyrmex. Ward and Brady also transferred both taxa as distinct genera in the older subfamily Myrmeciinae under the tribe Prionomyrmecini. In 2005 and 2008, Baroni Urbani suggested further evidence in favour of his former interpretation as opposed to Ward and Brady's. This view is not supported in subsequent relevant papers, which continue to use the classification of Ward and Brady, rejecting that of Baroni Urbani. The ant is commonly known as the dinosaur ant, dawn ant, or living fossil ant because of its plesiomorphic body structure. Genetics and phylogeny Studies show that all hymenopteran insects that have a diploid (2n) chromosome count above 52 are themselves all ants; Nothomyrmecia and another Ponerinae ant, Platythyrea tricuspidata, share the highest number of chromosomes within all the Hymenoptera, having a diploid chromosome number of 92–94. Genetic evidence suggests that the age of the most recent common ancestor for Nothomyrmecia and Myrmecia is approximately 74 million years old, giving a likely origin in the Cretaceous. Nothomyrmecia and other primitive ant genera such as Amblyopone and Myrmecia exhibit behaviour similar to a clade of soil-dwelling families of vespoid wasps. The following cladogram generated by Canadian entomologist S. B. Archibald and his colleagues shows the possible phylogenetic position of Nothomyrmecia among some ants of the subfamily Myrmeciinae. They suggest that Nothomyrmecia may be closely related to extinct Myrmeciinae ants such as Avitomyrmex, Macabeemyrma, Prionomyrmex, and Ypresiomyrma. }} ==Distribution and habitat==

|alt=Map of Australia showing reported occurrences of Nothomyrmecia. Nothomyrmecia is present in the cool regions of South Australia within mallee woodland and especially old-growth areas populated with various Eucalyptus species, including Eucalyptus brachycalyx, E. gracilis and E. oleosa. Colony construction only occurs when the soil is moist. Nest entrance holes are difficult to detect as they are only in width, and are located under shallow leaf litter with no mounds or soil deposits present; guards are regularly seen. A single gallery, in diameter, forms inside a Nothomyrmecia colony. This gallery descends steeply into the ground towards a somewhat elliptical and horizontal chamber that is in diameter and in height. This chamber is typically below the soil's surface. ==Behaviour and ecology==

Foraging, diet and predators Workers are nectarivores and can be found foraging on top of Eucalyptus trees, where they search for food and prey for the larvae. Workers are known to consume hemolymph from the insects they capture, and a queen in a captive colony was observed consuming a fly. Workers also feed on sweet substances such as honeydew secreted by scale insects and other Hemiptera; one worker alone may feed on these sources for 30 minutes. Pupae may be given to the larvae if a colony has a shortage of food. Workers are able to lay unfertilised eggs specifically to feed the larvae; these are known as trophic eggs. Sometimes the adults, including the queen and other sexually active ants, consume these eggs. Workers transfer food via Trophallaxis to other nestmates, including winged adults and larvae; the anal droplets are exuded by the larvae, which are taken up by the workers. Nothomyrmecia is a polyandrous ant, in which queens mate with one or more males. In one study of 32 colonies, it was found that queens mated with an average of 1.37 males. After mating, new colonies can be founded by one or more queens; a colony with two queens reduces to a single queen when the nest is mature, forming colonies that are termed monogynous. The queens will compete for dominance, and the subordinate queen is later expelled by workers who drag her outside the nest. This uncertainty results from the suggestion that, because some colonies have been shown to have high levels of genetic diversity, worker ants could be inseminated by males and act as supplementary reproductives. ==Relationship with humans==

Conservation Before its rediscovery in 1977, entomologists feared that Nothomyrmecia had already become extinct. The ant was listed as a protected species under the Western Australian Wildlife Conservation Act 1950. With this said, it is unknown how widespread the species actually is, and scientists are not yet clear what, if any, threats affect it. Climate change could be a threat to their survival, as they depend on cold temperatures to forage and collect food. An increase in the temperature will prevent workers from foraging, and very few areas would be suitable for the species to live in. The cold winds blowing off the Southern Ocean allow Nothomyrmecia to benefit from the cool temperatures they need for night-time foraging, so an increase in sea temperature could also potentially threaten it. Pictures of the ant have been stencilled onto the pavements, and a large sculpture of Nothomyrmecia has been erected in the town. ==Notes==