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 overwintering 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.

Problem to humans -

Harlequin ladybirds have a tendency to aggregate in buildings in large numbers during autumn and winter.

• Many people find harlequin ladybirds a nuisance in the house, and do not wish to share their home with a few tens of thousands of harlequins
  
• As a defence mechanism many ladybird species exude a yellow fluid (called reflex blood) which has an unpleasant acrid smell, and which can stain soft furnishings
  
• When hungry, harlequin ladybirds will bite humans in their search for something edible. Ladybirds in houses, woken from dormancy by central heating, may bite people as there is no food available. The bites usually produce a small bump and sting slightly. There are a few documented cases of people having a severe allergic reaction to harlequin ladybirds.

Harlequin ladybirds damage soft fruit

• In late summer, when harlequin ladybirds are feeding up for the winter, they will seek ripe fruit and suck the juice from it to gain sugar. They thereby cause blemishes on late summer ripening fruits, such as pears, and reduce the value of the crop.