NSF-BSF: The biomechanics of long-distance flight in large beetles: Do smaller individuals fly better?

Insects have a tremendous effect on the world’s agriculture and forests. Their main dispersal mechanism is by flight, and some insects are capable of prolonged flights enabling them to disperse distances of tens of miles in a single flight. This study will examine how larval growth conditions leads to variation in the body size of adult beetles and how this variation in body mass affects their dispersal capabilities and endurance for prolonged flights.

The merit of the proposed work is its aim at understanding the relationship between the unsteady aerodynamics of insects during flight and their energy expenditure. Cutting edge tools will be used to measure and model the unsteady aerodynamics and flight energetics associated with flapping flight at an insect size scale. The insights from the study are expected to shed light on the factors contributing to dispersal of pest insects between infected areas, allowing design of science-based management programs for forests and parks.

It will also provide guidelines for the design requirements for efficient flapping unmanned aerial vehicles with improved prolonged flight capabilities. The work is interdisciplinary (Biology, Engineering) and will foster a synergistic international collaboration between Israeli and US undergraduate and graduate students. The results of the study will be disseminated to the scientific community in peer-reviewed journals and scientific conferences and to the general public through social media, websites and outreach programs in both countries.

The physiological and aerodynamic mechanisms improving flight endurance in insects are unclear due to limited understanding of the complex aerodynamic interaction between them and the wind during forward flapping flight. The proposed research will examine the flight behavior, aerodynamics, and energetics of the mango stem borer (Batocera rufomaculata), focusing on how intraspecific variation in body mass affects the ability to disperse large distances by flight.

B. rufomaculata is a large tree-boring beetle with larvae developing inside the stem of fig trees. Nutrient-deprived larvae developing inside dead host trees emerge as smaller adults with improved long-distance flight capabilities compared to larger adults emerging from live host trees. The study hypothesizes that smaller beetles are more efficient long-distance flyers due to favorable scaling of aerodynamics and flapping kinematics.

To test this hypothesis, the beetles will be tethered in a wind tunnel to fly at their preferred flight speed, in a set-up allowing correlation of their flapping kinematics (using high-speed cameras), the forces they produce during flight (using force transducers), and the flow fields formed in their unsteady wake (using particle image velocimetry, PIV) while measuring their metabolic energy expenditure using a technique based on a 13C isotope. These data will be complemented with numerical simulations of the beetle in forward flapping flight, providing benchmarks for the fluid-beetle interaction characteristics.

Finally, the flight of beetles in the field will be tracked using radio telemetry, and the allometry of flight-related traits will be evaluated. The results are expected to reveal the processes determining the relationship between larval development and insect flight performance.

This project is jointly funded by the Physiological Mechanisms and Biomechanics Program in the Division of Integrative Organismal Systems, Directorate for Biological Sciences, and the Established Program to Stimulate Competitive Research (EPSCoR).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.