Monday, February 02, 2009
They may not be out and about in the garden just yet, but the infamous Harlequin Ladybirds (Harmonia axyridis) may well be overwintering in your house. Just the other day I found a veritable infestation of them in one of the window frames in the dining room!
There's been a lot of comment and concern about this ladybird ever since it arrived in the UK in 2004. But why the worry, after all it is a predator, same as the native ladybirds? The problem is that these ladybirds are larger and have bigger appetites than our native species, and also have the advantage of a longer breeding season each year, so their population is rising rapidly. This means that there is a serious concern that they have the potential to out-compete the native species and so cause them to decline in number.
Open your window frames or peer behind the curtains and you may find all sorts of overwintering insects, including native ladybirds and perhaps the Harlequins too, so how do you know what you've found ? Harlequin ladybirds are larger than the native species (mostly 6-8mm long as opposed to 4-5mm for the native species) and although they vary in appearance, the two most common types are : Red with up to 21 small black spots, and black with either two or four large reddish orange blotches.
Harlequin ladybirds originated in Japan, but have since been introduced in to parts of Europe and the USA where they were used as biological controls of pests. Precisely how they ended up in the UK, no one seems quite sure, but although current advice is not to bother destroying them (they're too widespread!) their numbers and the areas they have colonised hare still being studied.
For more information about these insects, the latest distribution map and the survey visit
www.harlequin-survey.org
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