1. Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK

Correspondence to: A. L. R. Thomas Correspondence and requests for materials should be addressed to A.L.R.T. (e-mail: Email: adrian.thomas@zoo.ox.ac.uk).

Abstract

Flying insects generate forces that are too large to be accounted for by conventional steady-state aerodynamics^{1, 2}. To investigate these mechanisms of force generation, we trained red admiral butterflies, Vanessa atalanta, to fly freely to and from artificial flowers in a wind tunnel, and used high-resolution, smoke-wire flow visualizations to obtain qualitative, high-speed digital images of the air flow around their wings. The images show that free-flying butterflies use a variety of unconventional aerodynamic mechanisms to generate force: wake capture³, two different types of leading-edge vortex^{3, 4, 5, 6, 7}, active and inactive upstrokes⁸, in addition to the use of rotational mechanisms³ and the Weis–Fogh 'clap-and-fling' mechanism^{9, 10, 11, 12}. Free-flying butterflies often used different aerodynamic mechanisms in successive strokes. There seems to be no one 'key' to insect flight, instead insects rely on a wide array of aerodynamic mechanisms to take off, manoeuvre, maintain steady flight, and for landing.

1. Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK

Correspondence to: A. L. R. Thomas Correspondence and requests for materials should be addressed to A.L.R.T. (e-mail: Email: adrian.thomas@zoo.ox.ac.uk).