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Crematogaster Rogenhoferi Morphology

Mon, 20 Aug 2007 20:47:36 +0100

This great close-up clearly shows the 'double waist' of the Two Petioles. Knowing whether an ant has one or two petioles helps greatly with their identification. C. rogenhoferi has a distinctive arrangement of petioles. If you can examine their waist in detail you may see that the second petiole is attached to the gaster in a unique manner, and is known as a post-petiole, and so distinguishes Crematogaster ants from other families. For a diagram of the post-petiole arrangement, see Australian Ants online.

Check out the Ant Morphology illustration.

Note that the heart-shaped or triangular Gaster is raised on this individual. She may have been bobbing her Gaster in a state of wariness, or she may have been holding it in the raised aggressive position due to the intrusion of the camera.

The ant above is what I call a Mid Worker - she is 5mm long perhaps, and has an average sized gaster. Read more about sizes.

Feeding Ants

Sun, 19 Aug 2007 11:26:16 +0100

Ants, in general are omnivorous, and some species hunt and eat a surprising variety of larger prey.

Some ants actually farm aphids, and milk them for the honey-dew they produce.

Some ants cultivate special fungus, working hard to provide the ideal growing conditions.

I cannot be certain what my Thai tree ants' (Crematogaster Rogenhoferi) natural diet is, as there is so little information available; the web turns up absolutely nothing about these fascinating tree dwellers.

Generally speaking, ants enjoy non-citrus fruit, honey, and eating various species of insects and grubs / bugs.

Foods to try:

Grapes;
Melon;
Apple;
Ant Jelly;
Squished flies, woodlice, spiders, grubs n bugs.

You need to provide a varied diet, so experiment and see what your ants like, but don't skimp on the meat, you may well need to go hunting frequently, or buy some insects for them!

Honey will keep your ants happy and busy for hours, but they need other things, and meat! Remember that sweet foods will make your ants thirsty, so have fresh water readily available at all times. A colony is at risk of dying from dehydration if you do not supply water.

My Photo Blog often shows how excited my Thai tree ants get when fed flies and squished bugs; if you think ants are a bit dull, or your colony 'stays home' for ages, then I suggest you get them some fresh meat, and see what happens!

Ant Morphology

Mon, 30 Jul 2007 14:51:57 +0100

Insects are made up of three main parts, the head, alitrunk and the gaster. Ants have one or two bumps at their thin waists called petioles.

Ant antenna always have 'elbows', they are articulated with one joint.

Some ants sting, injecting formic acid.

Ants do not have lungs or hearts! Spiracles allow air in and out of their bodies, directly into the blood stream.

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Thai Tree Ants (Crematogaster Rogenhoferi)

Mon, 30 Jul 2007 13:05:13 +0100

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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