The Harlequin ladybird (Harmonia axyridis) arrived in Britain in 2004 after being introduced to USA in 1988. They are present quite widely in the south east of England and are gradually spreading north. Although this non native species could pose a serious problem to British species such as the two or seven spot ladybirds they do not present a public health threat.
However, these ladybirds have been known to live in houses in autumn and winter and can bite humans, particularly when waking from hibernation. The bite usually produces a small bump and may sting slightly, although in very rare cases an allergic reaction may occur. When disturbed, the ladybirds produce a yellow secretion which has an unpleasant smell and may stain soft furnishings
What do they look like?
Also known as the Asian multicoloured ladybird, the harlequin has a very variable appearance. In Britain the commonest form is orange with 15-21 black spots or black with two or four orange or red spots.
How do they live?
These ladybirds have 4 distinct life stages: egg, larva, pupa and adult. The adults lay eggs on host plants in early spring. The eggs hatch in 3 to 5 days and the larva stage lasts 12 to 14 days. The pupa stage which usually take place on leaves of fruit trees or plants lasts 5 to 6 days. The adult may live for two to three years and can lay over 1,000 eggs which may account for why the Harlequin ladybird occurs in such vast numbers.
Harlequin ladybirds feed on aphids in orchards but also feed off the larva of butterflies and moths and other ladybirds. They can also feed on fruit juices provided by orchard fruit, grapes, pollen nectar and honeydew.
Where are they found?
Harlequin ladybirds can be found most commonly on deciduous trees such as lime, sycamore and maple but also on coniferous woodland. They also inhabit such plants as nettles, reed beds and crop systems.
They are also attracted to lighter colours such as white, grey and yellow.
How do I control Harlequin ladybirds?
You should fill any small gaps or cracks around doorframes and fit a fine mesh to airbricks. This will help keep the ladybirds from entering your home.
Wipe down the area where ladybirds have been (window sills, door frames etc) with water and mild detergent. Ladybirds leave chemical traces (pheromones) where they have been in order to attract other ladybirds. Regularly washing down these areas will help prevent more ladybirds appearing.
Use a fast acting residual spray or general insecticide spray. It is best to use an insect spray before the ladybirds come inside. So spraying in September and October is best. Spray areas such as door frames, window frames and areas where pipes or wires enter your property. The spray acts as a chemical barrier which prevents ladybirds entering. Please be sure to follow the instructions for safe use of any product as shown on the container. Insect spray will be ineffective once ladybirds are indoors (late autumn, winter and early spring).
Dead ladybirds can be picked up by vacuum cleaner or dustpan and brush. You can use a narrow nozzle attachment to vacuum ladybirds, pay special attention to windows and light fittings as ladybirds are attracted to light.
Do not worry too much about ladybirds in the property, they do not present a health hazard and are likely to leave on their own accord in a few days or weeks.