![]() ![]() The anal stylus starts by rotating from a neutral position to squeeze out the fluidic waste. Tracking the angle θ between the anal stylus and the axis along the body of the insect reveals three consecutive phases: droplet formation, spring loading, and droplet ejection (Fig. Using high-speed imaging, we examine the dynamics of excretion of glassy-winged sharpshooters (GWSS, Homalodisca vitripennis, n = 5 individuals, N = 22 droplet ejections). Here, we ask: what are the fluidic, energetic, and biomechanical principles that enable tiny xylem sap-feeding insects to survive on a nutrient-sparse diet? Subsequently, sharpshooters must constantly and efficiently excrete their fluidic waste (~99% water, ‘leafhopper rain’), contributing to their role as plant disease vectors 9. To survive on this frugal diet, sharpshooter insects use large cibarial muscles and an efficient digestive system (filter chamber) to extract and filter large volumes of the xylem fluid (up to 300 × body weight/day 7, 8 compared to ~1/40 × body weight/day for humans). Plant’s xylem sap is very poor in nutritional compounds (95% water 5) and energetically costly to pump out since it is under negative tension 6 (≤ − 1 M P a). Millimeter-sized xylem-feeding insects exemplified here with sharpshooter insects ( Cicadellidea) face dual fluid dynamic challenges of surface tension due to their small size and energy constraints due to their xylem sap diet. Specifically, we focus on how excretion influences small-bodied animals’ behavior, morphology, and energetics since they face unique challenges due to their high metabolic rate 3 and physical limits set by the natural world 4. Although fluid feeding in insects (moths, mosquitoes, leafhoppers) has received considerable attention since Darwin’s time 1, little is known about the science and biofluid dynamics phenomena associated with waste elimination, despite having important ecological, morphological and evolutionary implications 2. The principles and limits of superpropulsion outlined here can inform designs of energy-efficient self-cleaning structures and soft engines to generate ballistic motions.Ĭonsumption of nutrients and subsequent waste elimination are hallmark functionalities of a living organism. ![]() ![]() Our model predicts that for these tiny insects, the superpropulsion of droplets is energetically cheaper than forming jets, enabling them to survive on an extreme energy-constrained xylem-sap diet. We combine coupled-oscillator models, computational fluid dynamics, and biophysical experiments to show that these insects temporally tune the frequency of their anal stylus to the Rayleigh frequency of their surface tension-dominated elastic drops as a single-shot resonance mechanism. To eliminate their high-volume excreta, these insects exploit droplet superpropulsion, a phenomenon in which an elastic projectile can achieve higher velocity than the underlying actuator through temporal tuning. Here we study millimeter-scale sharpshooter insects ( Cicadellidae) that feed exclusively on a plant’s xylem sap, a nutrient-deficit source (95% water). Although how feeding impacts animal form and function has been studied for more than a century since Darwin, how its obligate partner, excretion, controls and constrains animal behavior, size, and energetics remains largely unexplored. Food consumption and waste elimination are vital functions for living systems.
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