Workerless inquiline ant (Pogonomyrmex colei)

Workerless inquiline ant specimen
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Workerless inquiline ant fact file

Workerless inquiline ant description

GenusPogonomyrmex (1)

The rare ant Pogonomyrmex colei is referred to as a ‘workerless inquiline ant’ due to the fact that it lives commensally in the nest of its closest but much larger relative, Pogonomyrmex rugosu. Its host species is on average four times the size of male Pogonomyrmex colei and five times the size of the females (2) (3).

As a member of the Pogonomyrmex genus, Pogonomyrmex colei is a characteristic red colour and possesses a bearded structure, called a psammophore, which is used for digging and moving sand particles within its arid habitat. Both male and female Pogonomyrmex colei have wings, although these are smaller in the male and only the female can fly (2).


Workerless inquiline ant biology

Pogonomyrmex colei mates from mid-August through to October. Interestingly, mating behaviour is triggered by rainfall, a rare occurrence in this species’ arid habitat. The male will emerge from the host nest after light rain, although the female will only emerge after rainfall has penetrated several centimetres into the soil (2). Males of this species do not venture far from the nest site, a common behaviour in rare ant species as it increases the chance of finding a mate (4).

During copulation, in which only fertile offspring are produced, the host species, Pogonomyrmex rugosus will move around the copulating pair but will not interfere (4). The flightless male Pogonomyrmex colei then returns to the nest, while the females fly to new colonies, following pheromones laid down by Pogonomyrmex rugosus workers (2).

Colonisation of new nests by female Pogonomyrmex colei has a very low success rate, with 90 percent of females removed by the much larger Pogonomyrmex rugosus workers (2).


Workerless inquiline ant range

Pogonomyrmex colei is endemic to the U.S., living in central Arizona, southern Nevada, and south-eastern California (2).


Workerless inquiline ant habitat

Pogonomyrmex colei inhabits arid environments where its host species Pogonomyrmex rugosus is also found (2).


Workerless inquiline ant status

Pogonomyrmex colei is classified as Vulnerable (VU) on the IUCN Red List (1).

IUCN Red List species status – Vulnerable


Workerless inquiline ant threats

A rare species, Pogonomyrmex colei has a high mortality rate and a low establishment rate, meaning that numbers of this species are quickly diminishing (2).


Workerless inquiline ant conservation

There are currently no specific conservation measures in place for Pogonomyrmex colei.


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This species information was authored as part of the Arkive and Universities Scheme.


An interaction in which one species (the commensal) benefits from an association with a ‘host’ species, but the host is not affected.
A species or taxonomic group that is only found in one particular country or geographic area.
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
A chemical produced by an animal, which stimulates a behavioural or physiological response by another member of the same species.


  1. IUCN Red List (October, 2010)
  2. Johnson, R.A., Parker, J.D. and Rissing, S.W. (1996) Rediscovery of the workerless inquiline ant Pogonomyrmex colei and additional notes on natural history (Hymenoptera: Formicidae). Insectes Sociaux, 43(1): 69-76.
  3. Parker, J.D. and Rissing, S.W. (2002) Molecular evidence for the origin of workerless social parasites in the ant genus Pogonomyrmex. Evolution, 56(10): 2017–2028.
  4. Rissing, S.W. (1983) Natural history of the workerless inquiline ant Pogonomyrmex colei (Hymenoptera: Formicidae). Psyche, 90: 321-332.

Image credit

Workerless inquiline ant specimen  
Workerless inquiline ant specimen

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