Advice
RHS Help & Advice
Harlequin ladybird (Harmonia axyridis)
The harlequin ladybird is a new species to the UK. It has a voracious appetite and a longer breeding period than native species, and there are some fears it may out-compete native species.
Where has it come from?
Japan originally but it has been deliberately introduced into the USA and some mainland European countries as a biological control of aphids.
When did it reach Britain?
It was first detected in England in 2004.
How did it get here?
It may have come in on imported plants or cut flowers, it may have hitched a ride on a cross-channel lorry, or it may even have flown across the Channel.
What does it feed on?
The main food for both the larvae and adults are greenfly, blackfly and other aphids, plus some other garden pests, such as some scale insects. Like most native ladybirds, it will eat other insects if its preferred prey is unavailable. In North America, there is evidence to suggest that some native aphid predators are being eaten or out-competed for food resources and have declined in numbers as a result.
Will it do the same here?
Possibly, but it is too early to say if it will adversely affect native aphid predators, such as ladybirds, hoverfly larvae and lacewing larvae. A research group based at Cambridge University is monitoring the spread of the harlequin ladybird in Britain and its impact on other aphid predators.
Should I stamp on any harlequins I find?
No. It had already become too widespread and numerous in England before it was discovered for it to be eradicated. Killing them now will not affect its numbers and may lead to other insects mistakenly identified as harlequins being killed.
How do I recognise a harlequin?
The harlequin has many colour forms, some of which resemble those of native ladybirds. Common colour forms are black with two or four orange-red blotches on the wing cases, or red with up to 21 black dots on the wing cases. The harlequin is relatively large, being 6-8mm long; most native species with black wings and red blotches are 4-5mm long.
For pictures of harlequin colour forms visit www.harlequin-suvey.org/recognition_and_distinction.htm.
For pictures of native adult ladybirds visit www.ladybird-survey.org/UKladybirds/Ukladybirds.htm and click on the common names in the table.
Do I have to report harlequin ladybirds?
There is no obligation to do so. They can be reported online to www.harlequin-survey.org, giving details of when and where the insect was found (include the postcode for a garden). Alternatively, specimens can be sent, preferably alive in a stout container, to: Ladybird Research Group, University of Cambridge, 219D Huntingdon Road, Cambridge CB3 0DL. For the record to be confirmed it is necessary to send either the insect or a clear photograph. When photographing the ladybird, it is helpful to include a ruler or coin in the picture to give an indication of size.
Why are these ladybirds coming into my house?
Ladybirds overwinter as adult beetles in a variety of situations and some, like the harlequin and our native two-spot ladybird, like to seek shelter in buildings in the autumn. In a cool place they will cluster and settle down until they become active again in the spring. In heated rooms, harlequin ladybirds may continue crawling around during the winter.