Condoms and Clay: How Amazonian Cicadas Engineer Towering Mud Fortresses to Survive Metamorphosis

Scientists used condoms in the Amazon to prove that cicada clay towers are essential survival tools for airflow and predator protection.

By: AXL Media

Published: Apr 28, 2026, 6:41 AM EDT

Source: Information for this report was sourced from Earth.com

The Architectural Mystery of the Amazonian Floor

In the dense rainforests near Manaus, Brazil, the forest floor is dotted with mysterious clay structures that have long puzzled entomologists. These towers, constructed by the architect cicada Guyalna chlorogena, appear during the final nymphal stage before the insect emerges into adulthood. Recent research conducted through the Serrapilheira Institute has finally decoded the purpose of these mud chimneys. Far from being random mounds of excavated dirt, the towers are functional extensions of the cicada’s biology, designed to mitigate the extreme risks of the Amazonian environment during a period of high vulnerability.

Lifting the Defense Above the Ant Line

One of the primary functions of the towers is defensive, specifically targeting the constant threat of ground-dwelling predators. Marina Méga, an ecology doctoral student at the Federal University of Rio de Janeiro, led experiments to quantify the safety provided by these elevations. By placing bait on both the tower summits and the adjacent ground, the team discovered that ants were eight times less likely to be present on the towers. This height advantage is vital during the hours of metamorphosis, providing a vertical refuge that buys the cicada precious time when it is too physically committed to the emergence process to dig back into the soil.

Improvised Science and the Latex Air Test

To investigate how the towers assist with respiration, the researchers employed an unconventional scientific tool: 40 latex condoms. By slipping the condoms over the towers and sealing them with plastic film, the team created an airtight barrier that successfully blocked gas exchange. This induced immediate respiratory stress in the underground nymphs, who rely on the porous clay to vent carbon dioxide and intake oxygen. When the seals were removed the following day, the insects’ rebuilding efforts proved that they were actively monitoring and responding to the airflow quality within their structures, confirming the tower's role as a biological lung.