The intriguing physiological characteristics of cicadas have recently been the focus of a novel research study published in the eminent Proceedings of the National Academy of Sciences. Albeit minute in size, cicadas are renowned for their prodigious appetite and frequent urination habits, distinguishing them from the majority of their insect counterparts. Characteristically, this class of insects opts for energy-saving droplets of urine rather than potent jets. Adult cicadas have even been observed using their anal jets as defensive tactics against intruders, a fact that’s bound to haunt us as we approach the anticipated ‘double brood’ cicada season this spring.
While the scientific realm has ardently inspected the fluid dynamics of ingesting in insects, the case is quite contrary when it comes to scrutinizing their waste elimination process. This is according to Saad Bhamla, an esteemed member of Georgia Tech’s faculty, who ironically, points out that even the eminent Leonardo da Vinci was captivated by the behaviour of jets and the part played by fluid cohesion in the formation of droplets. Bhamla maintains that the elimination of waste is crucial to the regulation of any creature’s ecological and metabolic activities. Predictably, his research ventures have been dedicated to bridging this knowledge gap and challenging the old-fashioned, mammal-centered paradigms that presumably govern waste elimination in various species.
Previously, Bhamla’s team engaged in a comprehensive exploration of urination in the glassy-winged sharpshooters. These exotically named insects indulge in copious ingestion of water by piercing the xylem of plants (a specialised tissue transporting water from roots to stems and leaves) and feeding on the sap. The resulting frequency of urination is extraordinary, with sharpshooters expelling up to 300 times their body weight in urine daily. Defying conventional rules, they create droplets of urine at their anus and propel these away from their bodies at phenomenal speeds, achieving accelerations faster than a Lamborghini.
This exceptional strategy, termed ‘superpropulsion’, was discovered to be a remarkable energy conservation mechanism. The investigators associated the sharpshooter’s activity with a diver launching from a high-dive board. Their theoretical models indicate that this method consumes up to four to eight times less energy than continuously producing a urine stream. From an ecological standpoint, this impressive distance also reduces the risk of predators discovering them through chemical detection.
Notably, the sharpshooter isn’t a solitary example of insects adopting unique excretion strategies; the animal kingdom is replete with similar examples. Resilient ‘frass-shooters’, ‘butt-flickers’, and ‘turd-hurlers’ – such as skipper larvae with anal plate latches that expel solid pellets by increasing their blood pressure, and certain noctuid moths that kick pellets away using their thoracic legs – counter their predators with these dramatic actions. Nevertheless, the exclusive study of the glassy-winged sharpshooter marked the first-ever observation of superpropulsion in a living organism.
