Mound-Building Termite

A queen built for eggs

Macrotermes bellicosus is a fungus-growing, mound-building termite from Africa. Queens and kings are known to live as long as 20 years in the lab, while workers live only a few months. Queens of its genus, Macrotermes, are specialized egg-layers that produce about 20,000 eggs a day. Given how long they live, the researchers call them probably the most fecund terrestrial animals, meaning the most productive egg-layers on land.

In one wild study population in Ivory Coast, a colony’s median life expectancy once its mound appears is 6 years. Army ants that kill whole colonies are the major cause of chance deaths there once colonies are established.

Two kinds of workers

Workers are completely sterile. There are two worker castes, called majors and minors. Minors mostly work indoors, caring for young and building the mound. They are female and can develop into soldiers. Majors are male and generally do the more dangerous jobs, like foraging for food.

Workers change jobs as they age. In a study that tracked marked workers, they moved from caring for the queen to foraging between day 13 and day 25 after their moult into adults for majors, and between day 9 and day 32 for minors. Their traffic to a foraging arena was highest at 20:00 in the evening and lowest at 7:00 in the morning.

Fungus farmers

These termites grow a fungus of the genus Termitomyces on fungus combs inside the nest. The two live in an obligate mutualistic symbiosis, a partnership neither side can do without. The termites’ main food is dead wood, grass litter and dung.

Colonies reach high densities in African savannah, while in forests they are comparatively rare and found only in relatively open areas. In a three-year study of both habitats, savannah colonies reproduced annually, producing high numbers of offspring called alates. Forest colonies reproduced on average only once every 3 years.

Forest and savannah mounds In Ivory Coast’s Comoé National Park, mounds in the cooler gallery forest are dome-shaped with thick walls, while savannah mounds are more complex, with many ridges and thin walls. Savannah mounds have a very efficient circular airflow during the day. In the cooler forest, air moves upward less efficiently.