Forest ants manage to make the independent of the surrounding climate in an astonishing way. Their scattered dome heaps, which provide living space for hundreds of thousands of animals, are the most conspicuous and climatically efficient nest structures. They can reach up to 2 m in height and just as far in depth.
The nest dome is not only made up of easily transportable conifer needles, but also of other components such as small branches, stones and resin lumps. The opening or closing of entrances controls humidity and heating. Coarse and loosely layered material on the inside allows ventilation and prevents moisture build-up.
The nest dome as a solar collector is high in shady and low in sunny locations. In the early spring, workers sunbathe densely crowded on the nest dome, absorbing the heat and carrying it into the still cool nest interior. With sufficient colony strength and good nutritional status, ants generate enough metabolic heat to keep certain nest areas at a constant 26-28°C even on cold summer days.
Humidity reduction is necessary because apart from the danger of fungus, humidity dissipates heat. In areas with high rainfall, ants use the protection of treetops and the like. Dehumidification is actively practiced by constantly rearranging the heap material, i.e. dry material from the outside is transported to the inside and moist material from the inside to the outside.
If you manage to get along with the forest ants, you can also use their nest warmth. The comparatively tiny shiny guest ant Formicate- nus intitules has its nests exclusively in the nests of the forest ants. There it lives on the food exchange of the host animals.
Relationships with the environment
Ants build up very stable and individual-rich populations. This is only possible with enormous amounts of food. This is why ants attach great importance to their habitats. Essentially, ants need two forms of food: proteins and carbohydrates. Proteins, i.e. hunting prey and carrion, are especially important for the brood, which has to grow (biomass build-up). Carbohydrates are the fuel that enables the numerous workers to feed on their honeydew and plant juices.
Honeydew and plant juices
Plant sap suckers such as aphids, scale insects and cicadas only use part of the substances contained in the food during intestinal passage, the rest is excreted. Honey bees collect these “excreta” – the honeydew – from leaves etc. (forest honey), while ants take the coveted sap directly from the anus of the leaf suckers, which requires communication. When milking the plant louse, the ant strokes the abdomen of a louse with its antennae, which in turn strokes the ant’s head with its antennae-like hind legs and releases a sweet drop. The ant collects the droplets in its crop until it returns to the nest with a bloated abdomen.
Besides the main component of sugar, the honeydew contains minerals, vitamins, and amino acids. The latter is important for animal protein synthesis, accounting for up to 15% of the droplet mass. Therefore, some ant species can largely do without hunting for protein supply. Laius flavors, for example, live completely underground and cares for root lice. However, these root lice are not only “milked”, but – if necessary – also “slaughtered” and fed to the larvae.
Careful removal of the honeydew by the ants reduces the risk of fungus and is therefore important for both aphids and the plants concerned. Ants also offer the aphids a certain amount of protection from predators and sometimes even build burrows over their charges. In general, however, the protective power of ants is overestimated. Specialized aphid hunters such as ladybird, hoverfly and lacewing larvae are largely unaffected by ants. The relationship between ants and the various aphid species varies.
Certain species do not benefit from ants at all, while others thrive better with ant care than without. Still others cannot survive without ants in the long term, so there is a real symbiosis.