Jack Jumper

Appearance

Like its relatives, the ant possesses a powerful sting and large mandibles. These ants can be black or blackish-red in colour, and may have yellow or orange legs. The ant is medium-sized in comparison to other ''Myrmecia'' species, where workers are typically 12 to 14 millimetres long.

Excluding mandibles, jack jumpers measure 10 millimetres in length. The ant's antennae, tibiae, tarsi and mandibles are also yellow or orange. Pubescence on the ant is greyish, short and erect, and is longer and more abundant on their gaster, absent on their antennae, and short and suberect on their legs. The pubescence on the male is grey and long, and abundant throughout the ant's body, but it shortens on the legs. The mandibles are long and slender ), and concaves around the outer border.

The queen has a similar appearance to the workers, but its middle body is more irregular and coarser. The queen is also the largest, measuring 14 to 16 millimetres in length. Males are either smaller or around the same size as workers, measuring 11 to 12 millimetres.

Males also have much smaller triangular mandibles than workers and queens. The mandibles on the male contain a large tooth at the centre, among the apex and the base of the inner border. Punctures are noticeable on the head, which are large and shallow, and the thorax and node are also irregularly punctuated. The pubescence on the male's gaster is white and yellowish.

Naming

The specific name derives from the Latin word ''pilose'', meaning 'covered with soft hair'. The ant was first identified in 1858 by British entomologist Frederick Smith in his ''Catalogue of hymenopterous insects in the collection of the British Museum part VI'', under the binomial name ''Myrmecia pilosula'' from specimens he collected in Hobart in Tasmania.

Distribution

Jack jumper ants are abundant in most of Australia, being among the most common bull ant to be encountered. The ants can be found in the south-western tip of Western Australia, where it has been seen in the sand hills around Albany, Mundaring, Denmark and Esperance. The ant is rarely sighted in the northern regions of Western Australia. In South Australia, it is commonly found in the south-east regions of the state, frequently encountered in Mount Lofty , Normanville, Hallett Cove and Aldgate, but it is not found in north-western regions.

Behavior

Primarily diurnal, workers search for food during the day until dusk. They are active during warmer months, but are dormant during winter. Fights between these ants within the same colony is not uncommon. They are known for their aggression towards humans, attraction to movement and well developed vision, being able to observe and follow intruders from a metre away. This species is an accomplished jumper ants with leaps ranging from 2 to 3 inches . William Morton Wheeler compared jack jumper ants to "Lilliputian cavalry galloping to battle" when disturbed, due to their jumping behaviour. He further wrote that they also made a ludicrous appearance as they emerge from their nests, in a series of short hops.

Habitat

Jack jumper ants live in open habitats, such as damp areas, forests, pastures, gardens and lawns, preferring fine gravel and sandy soil. Colonies can also be spotted around light bushland. Their preferred natural habitats include woodlands, dry open forests, grasslands and rural areas, and less common in urban areas.

Reproduction

Queens are polyandrous, meaning that queens will mate more than once; queens mate with one to nine males during a nuptial flight, and the effective number of mates per queen ranges from 1.0 to 11.4. Studies show that most queen ants will only mate with one or two males. If the number of available male mates increases, the number of effective matings per queen decreases. Colonies are polygynous, meaning that a colony may house multiple queens; there are on average one to four queens per colony, and in multiple-queen colonies, the egg-laying queens are unrelated to one another. Based on a study, 11 of the 14 colonies tested were polygynous , showing that this is common in jack jumper colonies. When the queen establishes a nest after mating, she will hunt for food to feed her young, making her semi-claustral. Nests can hold as few as 500 ants or as many as 800 to 1,000. Excavated nests typically have populations ranging from 34 to 344 individuals. Jack jumper ant workers are gamergates, having the ability to reproduce in colonies with or without queens.

Colonies are mainly polygynous with polyandrous queens, however, polyandry in jack jumper colonies is low in comparison to other ''Myrmecia'' ants, but it is comparable to ''M. pyriformis'' ants. In 1979, Craig and Crozier investigated the genetic structure of jack jumper ant colonies, and although queens are unrelated to each other as mentioned previously, the occurrence of related queens in a single colony was possible. During colony foundation, there are suggestions of dependent colony foundation in jack jumper queens, although independent colony foundations can occur, as the queens do have fully developed wings and can fly. Isolation by distance patterns have been recorded, specifically where nests that tend to be closer to each other were more genetically similar in comparison to other nests farther away.

As colonies closer to each other are more genetically similar, independent colony foundation is most likely associated with nuptial flight if they disperse far from genetically similar colonies they originate from. Inseminated queens could even seek adoption into alien colonies if a suitable nest site area for independent colony foundation is restricted or cannot be carried out, known as the nest-site limitation hypothesis. Some queens could even try to return to their nests that they came from after nuptial flight, but end in another nest, in association that nests nearby will be similar to the queens birth nest.