A new ladybird has arrived in Britain. But not just any ladybird: this is the harlequin ladybird, Harmonia axyridis, and the most invasive ladybird on Earth.
The harlequin has three main colour formations in the UK and is a large species (7mm):
- Orange/yellow with up to 21 black spots on the wing case (although some can lack all spots), brown legs and an out-turned edge to the wing case
- Black with two red spots
- Black with four red spots
The adult bug is bigger and rounder than the seven-spot ladybird native to the UK.
The Harlequin can be up to 7mm long and is more likely to be orange rather then red but can also come in other colours including black with red spots and yellow and black.
And just behind its head it has a white plate with a big black ‘M’ on it.
Distinguishing the harlequin ladybird from other British species:
- If it’s less than 5 mm (1/5 inch) in length, it is definitely not a harlequin ladybird.
- If it’s red with precisely 7 black spots, it is a 7-spot ladybird.
- If it has white or cream spots, it is a striped ladybird, an orange ladybird or a cream-spot ladybird.
- If it is large, burgundy coloured and has 15 black spots, it is an eyed ladybird
- If it has an orange pronotum, and fine hairs all over the elytra, it is a bryony ladybird
- If it is black with four or six red spots, two of which are right at the front of the outside margin of the elytra, it is a melanic form of the 2-spot ladybird.
Why should we be concerned about the arrival of the harlequin ladybird?
Threat to wildlife –
Harlequin ladybirds can seriously affect native ladybird species
- Harlequin ladybirds are very effective aphid predators and have a wider food range and habitat than most other aphid predators (such as the 7-spot ladybird) and so easily out-compete them.
- Harlequin ladybirds do not have a requirement for a dormant period before they can reproduce, as some ladybirds have (e.g. 7-spot and eyed ladybirds), and so have a longer reproductive period than most other species. In 2004 in London, harlequin ladybird larvae were found still feeding in late October, long after all the native species had sought over wintering sites.
- When aphids are scarce, harlequin ladybirds consume other prey including ladybird eggs, larvae and pupae, butterfly and moth eggs and caterpillars.
- Harlequin ladybirds can disperse rapidly over long distances and so have the potential for rapid geographic expansion.