One of the most spectacular and widely known long-distance migrations by insects is the multi-generational migration by Monarch butterflies Danaus plexippus, in North America. Monarchs are migrating north in spring to breeding sites as far north as southern Canada and returning to wintering sites in mountainous forests in Mexico. The migration distance and number of generations involved are now beaten by the European migratory butterfly, the painted lady Vanessa cardui. In one year the painted lady is migrating from tropical Africa to northern Europe and back, twice the distance the monarch butterfly is covering in the same time. The painted lady, unlike the Monarch butterfly which is hibernating in winter, reproduces all year around but at different latitudes. It takes the painted lady six generations to cover a round-trip distance of 15 000 km (up to 60 degrees of latitude and back). In some years (like in 2009) the painted lady shows massive migrations, which may be performed also at high altitudes out of sight from entomologists and migration watchers.
|Photo: Pål-Axel Olsson|
In a recent paper by Stefanescu et al. 2012 (now available as early view) published in Ecography we describe the migration phenology for the painted lady across its continuously breeding path from winter and early spring in tropical Africa via central Europe to the most northern locations in northern Europe in summer and back. The migration of the painted lady is spectacular and show the migration of a habitat generalist and highly polyphagous migrating butterfly adapted to migration in a temperate region. Radar observations show the selectivity to winds and use of high altitude flights to reach more distant areas for breeding which has been observed for other insects too and suggest that the migration strategy may be widespread among insects in temperate regions migrating long distances.
The data set included in the paper contains more than 60 000 observations from the Palaearctic and benefit strongly from national observation schemes (“citizen science”), such as those compiled in the Swedish “Artportalen”, included in LifeWatch Sweden. On the behalf of all co-authors - thanks to all who reported observations of this charismatic long-distance migrating butterfly!