March 21, 2008
Introducing... the Harlequin
Last week's brief spell of warm weather drew out some early emerging Harlequin Ladybirds (Harmonia axyridis).
It's amazing to think that when I left Britain 4 years ago this species had never been recorded here in the wild. Having been released to control aphid populations on mainland Europe, it was inevitable that it would eventually arrive in Britain, either naturally or on imported plants (there is even a record of an individual arriving in a suitcase from Canada!)
Why should we care? The species is a voracious predator of aphids, but also of other invertebrates, including the larvae of our native ladybirds. Given its propensity to reach high densities in its introduced range, the double whammy of competition and predation could seriously impact on the populations of a number of aphid predators (and their parasites). Additionally, they aggregate in large numbers in people's houses while searching for overwintering sites, making a mess and quite literally causing a stink by 'reflex-bleeding' a pungent fluid when threatened. In the US, sufficiently large numbers gather to feed on grapes around harvest time each year that they taint the taste of wine.
I've just joined a research team investigating the spread and potential impacts of the Harlequin - any sightings of you have of this species can be recorded here. Thanks to the efforts of the general public, the spread of the Harlequin through Britain has been well-documented: in just 4 years it has been recorded from most of England with a few records from Wales and Scotland in the last couple of years. We often receive specimens - dead and living - by post from people wanting confirmation of the ID. This is just part of a group collected in one person's house, and displays the remarkable diversity of patterns on the wing cases (elytra).
Over the next few months I hope to post more about Harlequins and our native ladybird species (I now have an identification key) - watch this space!
Posted by rjhall at March 21, 2008 10:35 PM