Sunday, 1 September 2013

Harlequins take over

Most of the ladybirds in our garden this year are Harlequins, which probably explains why we haven't had any problems with aphids. Harlequins are not native to the UK and were introduced as a biological control for aphids. They breed more quickly than our native species and have a voracious appetite, making them ideal as a means of pest control. The downside is that they out-compete and now pose a serious threat to other ladybirds. When aphids are scarce harlequins will eat other ladybird eggs, larvae and pupae, butterfly and moth eggs and caterpillars.

Below is a photo I took of a Harlequin next to its pupal case on a celeriac leaf.

Harlequin ladybird next to its empty pupal case

This example seems to conform to the standard descriptions I have seen on various sites, but they are very variable in appearance. There is information on how to recognise the Harlequin on the Harlequin Survey site at, and there is also an identification guide for Harlequins and common British ladybirds. The larvae, on the other hand, are very distinctive and the Harlequin is particularly spiky. The Ladybird Survey has a good identification guide for larvae of UK ladybirds.

Harlequin ladybird larva
So, given that Harlequins have almost reached pest status in the UK, am I doing anything about it? I'm afraid that at the moment I am going to be selfish about this and leave them be. They are doing a good job of keeping the aphids at bay and I'm having a hard job finding non-Harlequin ladybirds in the garden. I may change my mind, though, should they decide to take up residence in the house for the winter.

Further information on Harlequins and other ladybirds can be found on the Harlequin Ladybird Survey and UK Ladybird Survey websites. There is also a good overview of the issues involved in an article on the Wellcome Collection blog Ladybirds: friends or foe?

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