Strumigenys perplexa (Fr. Smith 1876)

Compiled by Warwick Don & Richard Harris

Biostatus: Introduced

Classification

Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Dacetonini
Genus:	Strumigenys
Species:	perplexa

Common name(s)

Snappy detritus ants (Andersen 2002) (Generic common name)

Synonyms (WWW5)

Orectognathus perplexus Smith, Strumigenys antarctica Forel, Strumigenys leae Forel

Origin

According to Shattuck (1999), there are 168 known species and subspecies of Strumigenys, found worldwide in the tropics and subtropics. Seventeen species are known from Australia. An Australian species, Strumigenys perplexa has become established in New Zealand, while its permanent workerless inquiline, the social parasite S. xenos has only been collected once in this country. Brown (1958a) suspects a probable introduction of S. perplexa from Australia in historical times. It was first collected at Tairua, Coromandel Peninsula in the early 1870s.

Distribution

S. perplexa inhabits native forests on the northern half of the North Island, on the Three Kings Is. (Taylor 1962; Don 1994), and on northern offshore islands, and has also been sampled in pasture and in urban areas in gardens as far south as Nelson. There are also single collection records from Fiordland and the Chathams.

General Description

Identification

The antennae are 6-segmented. The mandibles resemble those of Orectognathus , except that they are slightly curved. Propodeum with a pair of short, acute spines. Many species possess masses of sponge-like cuticle on the sides of the petiolar nodes and lower part of the gaster.

Diagnostic features of the worker

Length 2.2 to 2.7 mm; sponge-like cuticle present; colour yellowish-brown.

[Strumigenys perplexa] head. Image: April Nobile (Specimen code: CASENT0172367). www.antweb.org Image — Strumigenys perplexa head. Image: April Nobile (Specimen code: CASENT0172367). www.antweb.org

Strumigenys perplexa profile. Image: April Nobile (Specimen code: CASENT0172367). www.antweb.org

[Strumigenys perplexa] dorsal view. Image: April Nobile (Specimen code: CASENT0172367). www.antweb.org Image — Strumigenys perplexa dorsal view. Image: April Nobile (Specimen code: CASENT0172367). www.antweb.org

Biology

Colonies are small (40 to 200 workers), may contain several dealate queens and are seldom seen. In Australia, nests occur in rotten wood, in small rotting seeds or twigs, or directly in the superficial soil layers (Brown 1958a). Foraging is probably hypogaeic (beneath cover), given its frequent occurrence in leaf litter samples, and that its diet is comprised mainly of collembolans. Also occasionally caught in pitfalls. Spring-trap mandibles and an immobilizing sting ensure the successful hunting of small creatures in or beneath the leaf litter. A slow gait and employment of a death-feigning reaction promote the difficulty in detection. Queens forage like workers.

Pest Status

Rarely encountered, and mostly sampled in forest habitats. Unknown impact in native systems, where it probably feeds on Collembola, but not considered a pest.