Grow, Expand, Remodel

Cornitermes cumulans nest
Photo: Marcella Cosarinsky*

Cornitermes cumulus is a neotropical termite that builds mounds more than a meter high. An average of over 300 mounds per hectare are found in pastures, cultivated lands and Savannas in Brazil and Paraguay. How are tiny insects able to construct such a large structure?

Like all large projects, they start small and then grow. A nest is originally founded by a mated female and her male partner. Together they excavate an underground chamber (copularium) where they rear the first brood. This brood becomes workers that will build a large structure.

The workers create walls from soil and saliva that extend just above the soil surface creating a flat mound. A hive or “habitacle” where the brood is raised is attached to the walls in the center of the mound. As the colony grows the habitacle must be expanded, but is confined by the walls. The workers add to the wall on the outside and remove material from the insides of the wall to create more interior space. Workers build galleries between the outer wall and the habitacle that help support and protect the colony. Wall building and removal occurs at the top of the mound as well as on the sides. The habitacle exapands upward as well as outward so it is located in the center of the mound but its height is relocated above the soil surface.

The termites are able to change the consistency of the walls they create. When the mound is small, the walls are made of fine grain particles. As the mound becomes large, the walls are made from coarser particles. This change can affect the ventilation of the mound. Although they may appear as a “simple mound of soil” on the outside, the mounds are remarkably complex structures.

*Marcela I. Cosarinsky. The Nest Growth of the Neotropical Mound-Building Termite, Cornitermes cumulans: A Micromorphological Analysis. Journal of Insect Science 11(122):122 · September 2011