''Megadromus antarcticus'', also known as the “Alexander beetle”, is a member of the

Carabidae Ground beetles are a large, cosmopolitan family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it is one of the 10 most species-rich animal fami ...

(ground beetle) family and only found in the

Canterbury Canterbury (, ) is a City status in the United Kingdom, cathedral city and UNESCO World Heritage Site, situated in the heart of the City of Canterbury local government district of Kent, England. It lies on the River Stour, Kent, River Stour. ...

region of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

.Landcare Research, N. Z. (2015). New Zealand Land Invertebrates - Megadromus (Megadromus) antarcticus (Chaudoir, 1865). Retrieved from https://biotanz.landcareresearch.co.nz/scientific-names/c41ad33a-5c41-4446-8505-85508811bca7 ''Megadromus antarcticus'' are easily recognized by their iridescent green colouration.

Description

''Megadromus antarcticus'' size can range in length from 22mm to 34mm.Britton, E. B. (1940). The Carabidae (Coleoptera) of New Zealand. Transactions and Proceedings of the Royal Society of New Zealand, 69, 484. ''Megadromus antarcticus'' is a member of the

Adephaga The Adephaga (from Greek ἀδηφάγος, ''adephagos'', "gluttonous") are a suborder of beetles, and with more than 40,000 recorded species in 10 families, the second-largest of the four beetle suborders. Members of this suborder are collect ...

suborder which is morphologically defined by the presence of liquid feeding mouth parts as larvae and once matured, has six abdominal ventrites and pygidial glands.Lovei, G. L., & Sunderland, K. D. (1996). Ecology and behavior of ground beetles (Coleoptera: Carabidae). Annu Rev Entomol, 41(1), 231-256. Adephaga such as ''Megadromus antarcticus'' are also characterized by being well-proportioned with prominent

mandibles In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

, long slender legs and straight elyra. Adephaga are

cursorial A cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. cheetah) or if it can keep a constant speed for a long distance (high endurance). "Cursorial" is often u ...

beetles which means they are adapted specifically for running. ''Megadromus antarcticus'' is considered black - greenish with the brims of the

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on ea ...

and

elytra An elytron (; ; , ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometimes alterna ...

a metallic green colour. This colouring gives ''Megadromus antarcticus'' a fascinating appearance which has also been referred to as iridescent green.Butcher, M. R., & Emberson, R. M. (1981). Aspects of the biology of carabid beetles of Ahuriri Bush Scenic Reserve, Banks Peninsula. Mauri ora, 9, 59-70.

Distribution

Natural global range

''Megadromus antarcticus'' is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to New Zealand.Fountain, E. D. (2013)
Time travelling weevils: Unravelling the evolutionary past of Hadramphus using historical and modern DNA.
Unpublished doctoral thesis, Lincoln University, Lincoln, New Zealand.

New Zealand range

''Megadromus antarcticus'' is common throughout much of the Canterbury region. Their range extents from a northern limit in the Waikari area, to the coast in the east, comprising Banks Peninsula, as far south as the Cave area in South Canterbury, and to the lower reach of the Southern Alps in western Canterbury. Because ''Megadromus antarcticus'' is flightless it has limited

biological dispersal Biological dispersal refers to both the movement of individuals (animals, plants, fungi, bacteria, etc.) from their birth site to their breeding site ('natal dispersal'), as well as the movement from one breeding site to another ('breeding dis ...

ability. Additionally the braided rivers of the Canterbury plains present a significant obstacle to ''Megadromus antarcticus''.

Habitat preferences

''Megadromus antarcticus'' is a

generalist A generalist is a person with a wide array of knowledge on a variety of subjects, useful or not. It may also refer to: Occupations * a physician who provides general health care, as opposed to a medical specialist; see also: ** General pract ...

predator so can be successful in variety of different habitats. A very common habitat for ''Megadromus antarcticus'' to be sighted is in home gardens.Johns, P. (1986). Arthropods of Banks Peninsula reserves: Zoology Department, University of Canterbury. Other common ''Megadromus antarcticus'' habitats include urban areas, agricultural areas, native forests and exotic forests. They are also frequently been found amongst grassland log sites.Anderson, S. J. (2000). Distribution, habitat associations, and activity patterns of two endemic Banks Peninsula carabid beetles, Mecodema howitti and Megadromus guerinii. Unpublished doctoral thesis, Lincoln University, Lincoln, New Zealand.

Life cycle/phenology

The incubation period of ''Megadromus antarcticus'' eggs varies dependent on the time of year. This incubation period can range from just over four weeks for eggs laid in late August to three weeks for eggs laid in February. ''Megadromus antarcticus'' females do not leave their egg chamber to feed during this period making them particularly attentive parents.

Diet and foraging

''Megadromus antarcticus'' is considered a generalist predator. This allows it to feed on variety of different insects and larvae that live in habitats similar to its own. Prey of ''Megadromus antarcticus'' includes some species of slugs which are considered pests to the New Zealand agriculture industry.Fountain, E. D. (2013). Chapman, R. B., Simeonidis, A. S., & Smith, J. T. (1997). Evaluation of metallic green ground beetle as a predator of slugs. Proceedings of the Fiftieth New Zealand Plant Protection Conference, 51-55. In a study conducted in controlled conditions, ''Megadromus antarcticus'' preyed on both ''

Deroceras invadens ''Deroceras invadens'' is a species of air-breathing land slug, a terrestrial pulmonate gastropod mollusc in the family Agriolimacidae. Until 2011, this widely distributed species was known as ''Deroceras panormitanum'', and earlier as ''Derocera ...

'' and ''

Deroceras reticulatum ''Deroceras reticulatum'', common names the "grey field slug" and "grey garden slug", is a species of small air-breathing land slug, a terrestrial pulmonate gastropod mollusc in the family Agriolimacidae. This species is an important agricul ...

'' (grey field slug) with an average consumption rate of 0.55 slugs per day.

Predators, parasites, and diseases

Coleoptera Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

which includes ''Megadromus antarcticus'' are the most common insects which

morepork The morepork (''Ninox novaeseelandiae''), also called the ruru, is a small brown owl found in New Zealand, Norfolk Island and formerly Lord Howe Island. The bird has almost 20 alternative common names, including mopoke and boobook—many of t ...

prey upon.Haw, J. M., and M. N. Clout. (1999). Diet of morepork (Ninox novaeseelandiae) throughout New Zealand by analysis of stomach contents. Notornis, 46, 333-345. '' Circus approximans'' (Australasian harrier) are a bird of prey very common to the Canterbury region and 8% of their diet also consists of Insecta (insects) which includes ''Megadromus antarcticus''.Baker-Gabb, D. (1981). The diet of the Australasian harrier (Circus approximans) in the Manawatu-Rangitikei sand country, New Zealand. Notornis, 28, 241-254. At least one undescribed species of mite belonging to the genus ''Micromegistus'' has been found living on ''Megadromus antarcticus''.

References

External links

Citizen science observations of Alexander beetles.
* ''Megadromus antarcticus'' discussed on

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Critter of the Week ''Critter of the Week'' is a weekly RNZ National programme about endangered and neglected native plants and animals of New Zealand. Beginning in 2015, ''Critter of the Week'' is an approximately 15-minute discussion between Nicola Toki of the ...

''
17 November 2023
{{Taxonbar, from=Q13825622 Pterostichinae Beetles of New Zealand Endemic fauna of New Zealand Beetles described in 1865 Endemic insects of New Zealand Taxa named by Maximilien Chaudoir