Saves energy

Cicada species shoots urine drops every second

(Bild: Challita et al., Nature Communications)

Certain dwarf cicadas have an immense throughput of food. Day after day, they therefore eject around 300 times their body weight in the form of small droplets of urine from their rear end. The whole thing is probably a strategy of the insects to save energy, US researchers report.

This is made possible by a kind of specialized device, as a team led by Saad Bhamla from the Georgia Institute of Technology writes in the journal "Nature Communications". The researchers' videos show how the little animals shoot tiny droplets almost every second. When they evaporate, they leave behind a residue that gives plants and fruit a whitewashed appearance.

Insects feed on xylem sap
By way of comparison: according to the researchers, the daily amount of excrement in humans corresponds to an average of only around 2.5 percent of their body weight. According to the researchers, the cicadas (scientific name Homalodisca vitripennis), which are only a few millimetres in size, feed exclusively on so-called xylem sap, which is very low in nutrients and consists almost exclusively of water.

(Bild: Challita et al., Nature Communications)

The animals have to ingest correspondingly large quantities of the plant sap. They have an efficient digestive system that can filter large quantities of plant secretions and transport them through the body. To get rid of the water, these cicadas use a special mechanism that accelerates the excreted droplets, as the researchers write.

Probably a strategy to save energy
The whole thing is probably a strategy for the cicadas to save energy, as the energy consumption of other methods is significantly greater, write the researchers, who used numerous mathematical models for their study. By flinging the excrement far away, enemies are also less likely to become aware of the cicadas' whereabouts.