Thai Tree Ants (Crematogaster Rogenhoferi)

Three Castes: Major, Mid & Minor

I have cannot accurately measure them, but there appear to be three Worker castes.

Ridged Abdomen?

26/08/2007 - are there two types of gaster? On the left you can see the usual 'heart-shaped' gaster that distinguishes this species of ant. But on the right, is a picture I took of my Crematogaster rogonhoferi that shows there's another phenotype! Four ridges can clearly be seen, as the light reflects of the two upermost ridges.

What is the significance of this abdominal difference?

Are there really 3 sizes of workers, with two different gasters?

Crematogaster Rogenhoferi (or as I call them, Thai Tree ants) are from Thailand and the south and east of Asia I believe.

They may be found in the Philippines, Malaysia, 

They appear to have 3 or 4 polymorphs; a queen, alates, and perhaps three styles of worker ant.

The Major worker is only a little longer than the Mid worker, yet its gaster (abdomen) is significantly larger, and the whole ant seems considerably bulkier. The Mid worker (shown bottom-left) is the predominant caste, and then there are the Minor workers; at 3mm long they are quite quite small.

The workers have a pointed triangular gaster and it is shiny brown and perhaps banded.

The winged alates that fly off in summer are 9mm long and have a large fat gaster, they are black. Presumably the larger alates are females and the smaller alates are male.

I have not seen a queen, and there may be several queens in a colony, as C. rogenhoferi are polygynous.

Crematogaster Rogenhoferi like other Crematogaster ants perhaps, build their brown paper-like nests in trees, around 2.5 metres off the ground.

They are happy between 18 and 22C with a reasonably high humidity between 50 and 80%.

Their habitat requires sandy, loamy soil with moss and plant material and wood to forage within and build with.


Ridged Gaster?

To the right, you can see a photo of two ants, the one on the right with the unusually ridged gaster (abdomen) is brand new to me, and I am uncertain what it signifies.

Considering the 3 sizes of worker that are readily distinguishable within Crematogaster rogenhoferi, the additional gaster difference of these heavy ridges is note-worthy. You may wish to view the original photo of the ants on a grape.


Identifying the Species and Subspecies

The genus of Crematogaster (heart-shaped abdomen) was brought to the attention of Western science by Lundin 1831.

The species of Crematogaster rogenhoferi was identified by Mayr in 1879.

The species of Crematogaster rogenhoferi has five subspecies,
Crematogaster rogenhoferi:

  • flava (Florel, 1886);
  • rogenhoferi (Mayr, 1879);
  • lutea (Emery, 1893);
  • costulata (Emery, 1895);
  • fictrix (Florel, 1911).

Crematogaster rogenhoferi are classed as 'species complex' meaning that they are indeed a unique species genetically (they only reproduce with their own kind) but it is not possible to tell the species apart by sight - they are morphologically similar / identical. - hence the monika, 'complex'.


References:

www.discoverlife.org

The ant nest of Crematogaster reogenhoferi, PDF science paper by Suparoek Wtanasit and Sopark Janarit [PDF; 460KB]



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