Ants – Nature’s Secret Power (2006)

Ants, bees and wasps make up only 3 percent of animal diversity yet they may constitute up to 50 percent of the total animal biomass in land habitats.

Bert Hölldobler is a leading entomologist (scientist who studies insects). He collaborated with ant biologist E.O. Wilson and developed the field of Sociobiology.

The documentary does an excellent job introducing us observations coming from both natural and laboratory setting. First observation comes from the European red wood ants (Formica polyctena). These ants are predatory and consume a very large amount of insects in forests. They even can attack other well-defended social insects such as bees and also can defend themselves fiercely by squirting formic acid from their abdomen. While the larvae of red wood ants feed on insects gathered from every corner of the forest, the adults have a high sugar honeydew diet excreted by aphids. Ants also have evolved the ability to domesticate other animals, plants and fungi.

The next two observations come from two ants living in Indonesia. First ant (Dolichoderus thoracicus) was discovered by Alfred Wallace. These ants are nomadic. They tend mealy bugs and carry them to productive parts of plants the same way humans herd their animals from one pasture to another. Many ant species have evolved this domestication capability. You can watch Formica palidefulva tending treehopper (Entylia carinata) larvae in the short video below:

Darwin’in Karıncaları / Ant tending treehopper larvae on a thistle. from Uzay Sezen on Vimeo.

The second ant (Camponotus spp.) from Indonesia is unusual in its behavior representing another example for co-evolution this time with pitcher plants (Nepenthes bicalcarata). These ants nest inside the tendrils of the pitcher plant. Accumulation of too much organic material inside the digestive fluid of the host pitcher plant can lead to putrefaction. Ants maintain a steady level of nutrients and defend the plant.

Biologists have shown that a pitcher plant has a remarkable adaptation for varying the slipperiness of the rim of its trap (the peristome). In Borneo, the pitcher plant (Nepenthes rafflesiana) traps sporadically large group of ants from the same species. In experiments where the trapping surfaces were kept continuously wet the plants no longer captured large groups of ants. When scout ants find a pitcher trap full of sweet nectar, they return to the colony and recruit many more ant workers. A super-slippery trap will capture most of these scout ants preventing recruitment of more ants. Now the story gets better: It seemed as if something plays with the stickiness dial on the pitcher plants traps. For part of the day the peristome stays dry and sugary to ensure that scout ants discover the candyland and get super excited to return to the colony. later on, the trap becomes wet and slippery and large numbers of recruited ants get captured. What plays with the stickiness dial?

The plant of course cannot sense the presence of ants and thus cannot actively switch on (or off) its traps. The “switch” is in the weather conditions: rain and air humidity changes turn the trap “on” or “off”. The plant can only take little influence by secreting nectar onto the trap surface. This is not enough to make the trap wet under dry weather conditions: the nectar evaporates too quickly. However, the sugar remains on the surface, and that helps to get the trap wet again earlier when the air humidity starts rising in the afternoon. (It is the same effect that makes your household sugar form clumps when you leave the jar open in humid conditions: sugar is hygroscopic, i.e. it draws humidity from the air).

Pitcher plants most certainly have a rich body of natural history.

Carnivorous Pitcher Plant Catches Ants by Changing Slipperiness of Peristome from Nature Documentaries on Vimeo.

Ants – Nature’s Secret Power also demonstrates that scientists can remarkably keep many ant species as a whole colony in captivity. Just like in the documentary perhaps you yourself always wanted to keep ants right where you lived but thought terrariums required the expertise and money only available through natural history museums or nature centers. Think again. It is indeed an art to maintain an ant colony. If you do it right you can join many people who do just that.

You can watch more ant related documentaries such as “Life inside the Colony” or “The empire of the desert ants” in Nature Documentaries. To see an interesting microscopy work on a Madagascar ant click here.

 

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