Dimensional Analysis of Mountain Pine Beetle Flight

The Mountain Pine Beetle (MPB) is one of the most destructive pests in the pine forests of Western North America and has proven difficult to control. As the MPB disperses through flight, the study of MPB flight endurance and range is critical to estimating and controlling their spread. As the behavioral characteristics of the MPB limit free-flight measurements, flight mills (captive-flight apparatus that limit an insect to flight circular fixed path) are commonly used instead. We characterize the flight performance of the MPB on a flight mill using recent dimensional analysis of unsteady airfoil flows. The results propose specific, quantitative improvements for estimates of MPB dispersion.

Moreover, while it has been established in the literature that peak cruising performance for flapping wings, across many different species, lies within an optimal range of Strouhal numbers of 0.2 < St < 0.4, all observations of tethered MPBs in this work have been with Strouhal numbers greater than 2, which is more characteristic of rapid accelerations or escape maneuvers than efficient cruising. This indicates that the MPB consumes an extraordinary amount of energy on a flight mill, meaning that existing flight-mill derived flight range and endurance estimates may be significant underestimates.