Cataulacus mckeyi Snelling

Type location Cameroun (Snelling, 1979a, illustrated with SEM photographs) collected near Lake Tissongo, Douala-Edea Reserve, by Doyle McKey; workers with males and females .

Snelling's description (1979a) is at

WORKER - TL ca 3.3 mm, HW ca 0.96 (Gaume & McKey,1999); diagnostic features as in key.
From Snelling's (1979a: 5, illustrated, all forms) description - TL 3.58-4.04, HL 0.86-0.94. Head about as long as broad; head and alitrunk dorsa with abundant erect, flattened hairs; and hairs arising from punctures wider than the hairs. Dorsum of head with fine rugoreticulum, fairly shiny, puctate especially on vertex. Alitrunk dorsum weak rugoreticulum, but meshes faint so that longitudinal rugae dominate. First gastral tergite moderately shiny with fine medial longitudinal rugulae

This ant is an obligate inhabitant of the ant-plant Leonardoxa africana africana (Caesalpinaceae; denoted as ssp L4 or T4 in earlier papers) in Cameroun . This rain forest understorey tree is a very specialised myrmecophyte, which has evolved so as to have an obligate mutualistic relationship with Petalomyrmex phylax (see McKey studies for more details). Some 75% of all the trees are occupied by P. phylax but the remainder are occupied by Cataulacus mckeyi. Whereas P. phylax actively patrols all immature leaves, removing or dislodging potential small insect herbivores, Cat. mckeyi has smaller and much less active colonies doing little or nothing to protect the young leaves. Both ant species, however, get most of their sustenance from extra-floral nectaries on mature leaves. Thus, as Cat. mckeyi appears to convey no real benefit on the host tree, it is regarded as a parasite of the Leonardoxa-Petalomyrmex relationship. Gaume & McKey (1999) knew of no other plant-ant to be an obligate non-protective parasite of its sole host-plant species.

As the host tree is found only in a limited area of coastal rain forest in Cameroun (approximately that shown as the "area of 2001 collections" in Map 7, the geographical range of the ant is pretty well known - from ca 4°28'N to 2°34'N, and no further than 10°25'E.

In its host Cat. mckeyi makes entrance holes into the domatia of a precise size such that the hole can be blocked by the head of a single worker.

The photomontage is of a specimen sent to me by Professor McKey. The flattened body form and very dense short hairs, plus the block-like pedicel segments are distinctive. The head is convex with no obvious denticles and large eyes, plus all over dense spiculation. The specimen, however, is somewhat smaller than Snelling. Smelling didi not give any details of colour and his SEM photographs are far from clear. Other images can be seen in the folder at -