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Strumigenys xenos Brown 1955

Compiled by Warwick Don & Richard Harris
Biostatus: Introduced


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

Common name(s) 

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


None documented.


Strumigenys xenos is a social parasite of the introduced Australian ant, Strumigenys perplexa. It does not have its own nest or workers and lays it eggs in the nest to S. perplexa. S. xenos is an obligate resident in the nests of its host in that it is unable to survive outside the host colony. It would appear therefore that the only feasible method of entry into this country was in an intact nest of its host species. The first and only confirmed record of S. xenos in New Zealand comprises a single dealate female (this species is workerless), extracted from leaf mould by R.W.Taylor at Paihia, Bay of Islands, on 7 February 1959 (Taylor 1968).


Although this species has been collected only once, given the small size of S. perplexa colonies and thus the low probability of finding or sampling a nest, it can be assumed with some confidence that S. xenos is probably far more widespread than the sole record would suggest. Because this species is only to be found in the nests of its host, it is not surprising that litter or leaf mould samples reveal only foraging workers, and the occasional foraging queen, of the host species.

General Description


The antennae are 6-segmented. For additional features, see the next paragraph.

Diagnostic features of the queen

Winged (can become dealate); length 2.4 mm; in comparison with the queen of S. perplexa, the mandibles are smaller, shorter and more curved, the propodeal teeth are weakly developed, as are the masses of sponge-like cuticle; colour reddish-brown.


Brown (1955) observed the behaviour of S. xenos in a plaster nest of its host. The host workers continually tended the xenos queen. He saw no signs of hostility on the part of the host workers toward the xenos queen . When host workers were induced to move the brood following disturbance of the colony, the xenos queen was carried off in the mandibles of one or more of the workers. The association is clearly an intimate one.

Pest Status

Impacts not kown, but not considered likely to be a pest.