| Myrmecia nigriceps | |
|---|---|
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| Myrmecia nigriceps worker from Strangways, Victoria | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Family: | Formicidae |
| Subfamily: | Myrmeciinae |
| Genus: | Myrmecia |
| Species: | M. nigriceps |
| Binomial name | |
| Myrmecia nigriceps | |
| Synonyms | |
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Myrmecia nigriceps, also known as theblack-headed bull ant, is a species of ant endemic toAustralia. A member of the genusMyrmecia in the subfamilyMyrmeciinae, it was firstdescribed by Austrian entomologistGustav Mayr in 1862. These ants are large, varying from 19 to 23 millimetres (0.75 to 0.91 in) in length. However, colonies contain workers that are much smaller, usually half the size of normal workers. The queens are the largest while the males are the smallest, which can be easily identified due to their small mandibles.
Mainly nocturnalM. nigriceps is found in hot hilly areas and woodland, nesting underground in mounds. The ant's diet consists of sweet liquids from flowering plants and invertebrate prey, which are fed to the carnivorous larvae. Spiders are known to eat these ants, and echidnas consume the larvae and pupae. Like otherMyrmecia species,M. nigriceps ants possess a powerful and painful sting, and the venom is capable of inducing allergic reactions in sensitive people.
First identified byGustav Mayr in 1862, Mayr provided the first description ofM. nigriceps in his journalMyrmecologische Studien. The species was described under thebinomial nameMyrmecia nigriceps, based onsyntype workers collected fromGayndah andSydney.[2] In 1907, SwissmyrmecologistAuguste Forel treatedM. nigriceps as a variant ofM. vindex, but he eventually treated it as a synonym in 1910.[3][4]M. nigriceps was revived as a full species in 1933 by American entomologistWilliam Morton Wheeler, on the basis that it is distributed throughout Australia and its average size is greater thanM. vindex.[5] Scottish born Australian entomologistJohn S. Clark published onesynonym –Myrmecia fasciata, now considered a junior synonym.[6]M. nigriceps is a member of the genusMyrmecia, a part of the primitive subfamilyMyrmeciinae; most ancestors of the genus are only found in fossils, with the exception of the dinosaur ant (Nothomyrmecia macrops).[7][8]
Myrmecia nigriceps is a member of theM. gulosaspecies group, which is the largest species group of the nine groups described.[6] Thespecific name,nigriceps, is a combination of theLatin wordsniger, meaning "black", andcaput, meaning "head". This references the distinctive black head of the ant. With this said,M. nigriceps is commonly known as the black-headed bull ant.[9]
The size of worker ants varies from 19 to 23 millimetres (0.75 to 0.91 in). However, colonies contain very small workers, usually less than half the size of normal sized workers. Despite this, it is not known ifM. nigriceps ispolymorphic, due to little differences in morphology between the workers in comparison toFormicinae ants andPheidole, with soldiers having enormous heads.[10] The queens are the largest, measuring around 24 to 26 millimetres (0.94 to 1.02 in), and males being around similar sizes to worker ants at 18 to 20 millimetres (0.71 to 0.79 in).[11] The head andgaster are black, and the thorax, node, and postpetiole are either red or yellowish red, while theantennae andlegs are either yellow or testaceous. Themandibles andclypeus are also yellow.[11] The hair is short and yellow in colour, erect on the body and suberect on the legs. The pubescence (short, fine, soft hair) is white and abundant all over the postpetiole and gaster. The head is almost as broad as its total length, and the mandibles are longer than the head with 13 teeth present.[11]
The queen is similar in appearance to the worker, but they are the largest members of the colony. The hair is more abundant, and the head is broader. The mandibles are shorter and broader, although they are still as long as the head.[11] The wings are yellowish in colour and translucent in appearance. Males are the smallest members of the colony and can be easily identifiable by their perceptibly smaller mandibles. The hairs on males are the longest and most abundant among the worker and queen castes, with a long and broad head.[11]
Myrmecia nigriceps is similar in appearance toM. vindex, but several morphological characters distinguish these two species from each other. For example,M. nigriceps is generally larger thanM. vindex, and its head is either black or dark brown; the head is broader and more rectangular in workers. Thethorax andpedicel are noticeably darker and brownish red. The nests and behaviour, however, of both ants are similar to each other.[5]
Myrmecia nigriceps is distributed throughoutAustralia, but the ant is absent from areas in central Australia and the northern Australian coast.[5][12] The range ofM. nigriceps extends fromQueensland and down intoNew South Wales, theAustralian Capital Territory andVictoria.[11] It is also found inSouth Australia andWestern Australia.[5] Colonies are found in deserts, coastal areas,plateaus, woodland, native vegetation, hot hilly areas covered with scrubby vegetation and in rehabilitated sites, at elevations ranging from 300 to 460 metres (1,000 to 1,500 ft).[13][14][15][16]
Myrmecia nigriceps is a mound constructing species, although colonies can be found under logs.[5][17] Workers decorate the nest with a variety of items, includinglateritic pebbles and soil crumbs, in a similar fashion ofmeat ant (Iridomyrmex purpureus) nests.[17] Other items used for nest decorating include small stones and plant material.[18]
Myrmecia nigriceps ants arecrepuscular andnocturnal foragers, searching for food during the night.[19][20] Workers are found foraging onEucalyptus trees and issympatric with many species.[21] Adults arenectarivores, feeding on sweet liquids from plants and the larvae are carnivorous, feeding on captured invertebrates and other ants such asCamponotus workers and males.[5][18][22] Cockroaches, such asPlatyzosteria castanea andPlatyzosteria ruficeps, can repel attacks byM. nigriceps by discharging a secretion that disorientates the attacking workers.[23] Workers begin to forage one hour before sunset, with peak activity occurring during the twilight hours. These ants have excellent vision, having the largest eye lenses andphotoreceptors than any otherMyrmecia ant.[20] These ants are capable of discriminating the distance and size of objects moving nearly a metre away, sensitive to motion and will rapidly charge towards any moving objects to attack it.[24]
These ants are preyed on by theshort-beaked echidna (Tachyglossus aculeatus), and by spiders in the genusZenodorus, particularlyZenodorus metallescens.[25][26] Blindsnakes are known to consume the larvae and pupae of these ants.[27] Colonies are also ahost forM. inquilina, asocial parasite that lays its eggs inside the colony.[28]
Myrmecia nigriceps is an extremely aggressive ant, and larger colonies may rival other colonies of a differentMyrmecia species (such asM. gulosa) in terms of fierceness and pugnacity.[5] While the mandibles cause little to no pain in humans, the ant is equipped with a painful and powerful sting that is found at the end of the gaster. Like other ants, the sting is not barbed, and workers are able to sting multiple times without injuring themselves.[29] With amedian lethal dose (LD50) of 7.3 mg/kg, the venom is relatively weak in comparison to otherMyrmecia ants, whose LD50 is much lower.[a][31] However, in a 2011 study, at least one patient had an allergic reaction toM. nigriceps venom. This study also concluded that many otherMyrmecia species can causeanaphylaxis, as well as theGreen-head ant (Rhytidoponera metallica).[32] In theStarr sting pain scale, a scale which compares the overall pain of hymenopteran stings on a four-point scale, the sting ofM. nigriceps was ranked as two in pain, described as "painful".[33]M. nigriceps ants are able to enter colonies they do not reside in without being attacked; this may be due to these ants failing to recognise foreigners, or the consequences of ignoring workers from other colonies is low.[34][35]
Nuptial flight occurs after rain for several days, taking place between December and March. The males and virgin queens emerge from their nest, and unlike other species who mate on the ground or climb onto nearby trees or branches to fly off from, the reproductivealates will fly from the nest. Recorded nuptial flights usually took place on hilltops.[21]M. nigriceps queens are not known to seal up their entrance during colony foundation, unlike otherMyrmecia species such asM. regularis.[36] Workers can live exceptionally long, with an average lifespan of 2.2 years; maximum longevity in workers varied from 2.1 to 2.4 years.[37][38][39]
Media related toMyrmecia nigriceps at Wikimedia Commons
Data related toMyrmecia nigriceps at Wikispecies