Spiny Ants

Polyrhachis species

Spiny Ant, Polyrachis ornata Many species of spiny ant, like Polyrachis ornata, are attractively coloured. Golden-tailed Spiny Ant, Polyrhachis ammon The Golden-tailed Spiny Ant, Polyrhachis ammon, prefers open forest and woodlands. Polyrhachis australis Polyrhachis australis belongs to a group of hump-backed spiny ants with reduced spines. Polyrhachis australis nest A Polyrhachis australis nest among foliage. The ants web leaves together with silk produced by their larvae. Daemel's Spiny Ant Daemel's Spiny Ant is one of many species of Polyrhachis that nest in hollows in tree trunks and branches.

Most species of Polyrhachis have large spines on their bodies, from which they get their common name. There are well over 100 Australian species of spiny ants. They are quite large and often attractive ants that forage on the ground and run up and down the trunks of trees during the day. However a number of species are strictly nocturnal.

Most are black, but many have parts of their bodies, particularly the abdomen, covered in a thick layer of silver or golden hairs.

Their nesting habits are varied. Lots of species nest in the soil, usually under rocks and logs, but many others nest off the ground in hollow twigs and branches or within hollows in the trunks of trees. A few make their nests amongst the foliage of trees and bushes, webbing leaves together with silk produced by their larvae.

 

Spiny ants cannot sting but spray formic acid from a small circular hole (the acidopore) at the tip of the gaster.

Identification

All species of Polyrhachis are monomorphic, meaning that all the workers in a nest are similar in size. They have a waist made up of a single segment which often has spines. Most species also have spines on the mesosoma. The first segment of the gaster is long and usually covers at least half its length. Spiny ants, like most sugar ants (Camponotus spp.), do not have a metapleural gland, and lack an opening just above the base of the hind legs.

The Golden-tailed Spiny Ant, Polyrhachis ammon (length 6-8 mm) is one of several spiny ants with a bright golden gaster. The mesosoma has only one pair of strong spines at the rear. This species is common in open forest and woodland in coastal eastern Australia from north Queensland to Victoria. It nests in the ground under rocks and logs.

Dome-backed spiny ants such as Polyrhachis australis (length 4-6 mm), nest amongst the foliage of trees and shrubs by webbing leaves together with silk produced by the larvae. They incorporate fragments of vegetation into the silk. This group of spiny ants have a strongly arched mesosoma which has very short spines or none at all. Most species inhabit rainforest edges, open forest and woodland and some are common in suburban gardens in coastal Queensland.

Daemel's Spiny Ant, Polyrhachis daemeli, is one of many spiny ant species that nest inside hollows in tree trunks and branches. The workers are active during the day and are usually seen running up and down tree trunks. This species has pairs of spines on the front and rear of the mesosoma and has much of the body covered in silvery hairs. It is found in a variety of forest types and is common between Mackay and Brisbane.

 

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