The quagga mussel was discovered in a river near London recently and many are concerned about the havoc that it might wreak not only on native freshwater species, but also the damage that it can cause by blocking pipes, fouling lock gates and boat hulls. A number of species from the Caspian and Black Seas have made their way across Europe and are now poised to invade the U.K.   The woodland blog has previously reported on the threat to native ladybird species due to the ‘invasion’ of the UK by the harlequin ladybird.

Now Dr Bethan Purse, an ecological modeller at the Centre for Ecology and Hydrology and Dr Helen Roy, have investigated the spread and distribution of the harlequin ladybird in different U.K. habitats.   Dr. Purse was able to make use of the data collected in the UK ladybird survey.  This is a citizen science project, in which people across the U.K. are invited to send in pictures and descriptions of their sightings of the harlequin ladybird. a

Analysis of the data suggests that coniferous woodland may be a refuge for some of our native ladybird species. It seems that the harlequins ‘struggle’ to spread into this habitat. City habitats / environments, on the other hand, are more vulnerable to rapid invasion by the harlequin.

The data also suggests that there are differences in the spread of the two main forms of the harlequin.   One form is black with red spots – the melanic form, and the other is orange with black spots – the non melanic form.   The dark / melanic form seems to benefit from sunshine and thermal warming (dark colours absorb more heat energy) and this form had spread more than the non-melanic type. The darker form may warm up in the sunshine and become active quicker than the non-melanic form so has a selective advantage. (Cities and urban environments are often heat islands).