Discothyrea antarctica Emery 1895

Compiled by Warwick Don & Richard Harris

Biostatus: Endemic

Classification

Family:	Formicidae
Subfamily:	Proceratiinae
Tribe:	Ectatommini
Genus:	Discothyrea
Species:	antarctica

Common name

Clubbed trigger ant (Andersen 2002)

Synonyms

None yet recorded.

Origin

Discothyrea is regarded as a relict genus (Brown 1948); it comprises 27 known species, most of which occur throughout the tropics and subtropics (Shattuck 1999). A small number inhabit more temperate regions. Shattuck lists five species for Australia. One species, D. antarctica, is endemic to New Zealand. Brown (1958a) favours its derivation from Australian ancestors.

Distribution

This species inhabits native forests throughout the country and is commonly sampled in leaf litter and moss samples and pitfall traps.

General Description

Identification

Discothyrea are readily distinguished by the second segment of the gaster being strongly arched so that the sting faces forward, and by the oversized antennae due to the last segment being greatly enlarged.

Diagnostic features of the worker

Length about 2 mm; antennae short, 9-segmented with the last (apical segment) greatly enlarged to form a club; the single petiolar node is small and attached over most of its posterior face to the gaster; colour ferruginous (rusty redbrown); the mandibles with only a single tooth at the tip.

[Discothyrea antarctica] head. Image: April Nobile (Specimen code: CASENT0172126). www.antweb.org Image — Discothyrea antarctica head. Image: April Nobile (Specimen code: CASENT0172126). www.antweb.org

Discothyrea antarctica profile. Image: April Nobile (Specimen code: CASENT0172126). www.antweb.org

[Discothyrea antarctica] dorsal view. Image: April Nobile (Specimen code: CASENT0172126). www.antweb.org Image — Discothyrea antarctica dorsal view. Image: April Nobile (Specimen code: CASENT0172126). www.antweb.org

Biology

D. antarctica is a cryptobiotic ant like A. saundersi, nesting in soil, rotting logs and leaf litter. Colonies are small with fewer than 50 workers, so nests can easily be overlooked. Workers feign death when disturbed.

Brown (1958b) observes that Discothyrea “can be carried by commerce in plant roots and humus, and therefore often turns up in gardens. It should be expected in greenhouses and plant propagating beds wherever the temperature and moisture are held sufficiently high.” However, D. antarctica appears not to have exploited similar situations in this country. A morphologically similar and related genus, Proceratium, contains species that feed on arthropod eggs, as do some species of Discothyrea. D. antarctica is suspected to do likewise. Moore (1940) thought that this species might feed on mites living in the nests of other ants, and produced convincing evidence that this might be the case with respect to another endemic species, Huberia striata. Brown (1958b) reports seeing Discothyrea in the hilly parts of southeastern Australia occupying galleries in nests of other species of ants. Much remains to be discovered concerning the biology of Discothyrea species.

Pest Status

Impacts not known, but considered unlikely to be a pest.