Flight of the Butterfly

Red Admiral, Vanessa atlanta

One of the larger butterflies top be seen in Ireland, the Red Admiral (Vanessa atlanta) is a common sight of meadows, hedgerows and gardens with red bands and white spots contrasting boldly with its black upperwings (1). V. atlanta can be seen from May onwards in Ireland, with some individuals hibernating through the winter (2). Most, however, migrate from central and southern Europe to escape the summer droughts of these areas (3). Nettles (Urtica doica) are the food of choice of the larvae and these have begun to wither when migration begins. When the butterflies arrive in the north, there is a plentiful supply of food. Most adults will return south in late September to mid November when nettles are again in good supply.

Red Admiral, Vanessa atlanta

When returning south, V. atlanta engages in a high elevation return at a reported altitude of 2000 meters (3), riding on cool northerly winds. While flying it generates large forces that cannot be accounted for by conventional steady-state aerodynamics, as do all insects. Investigations into V. atlanta flight using wind tunnels and smoke-wire flow visualisations show that they use a variety of unconventional aerodynamic mechanisms to generate force, often different mechanisms in successive strokes (4)

References

1. Sterry, 2004 Collins Complete Guide to the Irish Wildlife p. 104
2. Chinery, 1987 Field Guide to the Wildlife of Britain and Europe p. 234
3. Mikkola, 2003 European Journal of Entomology 100 pp. 625-626
4. Srygley and Thomas, 2002  Nature 420 pp. 660-664