Monday 16 May 2011: The good and the bad?
Inbetween overseeing the boys' revision I managed to spend a bit of time in the garden. While I was doing some weeding I noticed these two ladybirds sitting side by side on an ox-eye daisy flower. Initially I thought they were a pair, but I quickly realised there were two different species.
At the top is a seven spot ladybird, a native British species that helps out gardeners. These beautiful beetles, and their larvae in particular, are avid and very active aphid predators, devouring more than 5,000 during their year-long life.
Underneath is a harlequin ladybird, a species which originated from eastern Asia. The harlequin ladybird was introduced to North America in 1988, where it is now the most widespread ladybird species on the continent. It has already invaded much of northwestern Europe, and arrived in Britain in summer 2004.
Harlequin ladybirds feed most commonly on aphids, but have a wide food range, also feeding on scale insects, adelgids, the eggs and larvae of butterflies and moths, many other small insects, including other ladybirds, pollen, nectar, and sugary fluids, including honeydew and the juice from ripe fruits.
There has been significant concern about the possible effects on our native British ladybirds, through competition for food sources and direct predation. As a result they are subject to an ongoing survey, details of which can be found here. This site also has lots of information about how to recognise them.
At the moment both species seem to co-exist quite happily in our garden, and if anything there seem to have been more seven-spot ladybirds around the last couple of years than previously. More widely, there have been suggestions that two spot ladybirds are showing a decline, but as insect populations tend to fluctuate markedly from year to year, it's perhaps too early to be sure of their influence.
PS Thanks forall the lovely comments and favourites for my poppy yesterday :)