The Harlequin Ladybird Harmonia axyridis: a beneficial new arrival or an unwelcome invader?
By Remy L. Ware and Michael E.N. Majerus
Department of Genetics, University of Cambridge
Part 2 - Impacts on humans
Many aspects of the behaviour of H. axyridis have led to its rise to pest status in North America.
- Ladybirds aggregate in winter and undergo a period of dormancy known as overwintering. Harmonia axyridis seeks out lightly coloured prominent surfaces, including the walls of buildings. Harlequins have been found overwintering in massive numbers (tens of thousands) outside and even inside people’s houses.
- When threatened, ladybirds release a yellow substance containing defensive alkaloids from their knee joints, known as reflex blood. This has a foul smell and can stain soft furnishings.
- When prey is scarce, H. axyridis will even eat pollen, nectar and the juice of ripe fruits. It has been known to blemish soft fruits such as raspberries and apples, reducing their value.
- A fondness for grapes has led the harlequins to visit vineyards and when they become mixed up with the crop, their alkaloids taint the flavour of the wine.
- There are also reports of harlequin ladybirds having a nibble at humans. In rare cases this has led to hospitalisation due to an allergic reaction.
Monitoring and control measures
Question : will natural population checks allow coexistence of H. axyridis with native ladybirds or will human intervention be required?
- The Harlequin Ladybird Survey has been set up to record the spread of H. axyridis through Britain
- The UK Ladybird Survey aims to monitor populations of British species and identify those most at risk
- Natural checks
- Natural parasites and parasitoids?
- Natural predators?
- Human intervention
- Pesticides? But these would have to be species-specific.
- Attractants? e.g. species-specific pheromone traps. Researchers are currently looking at this possibility.
- Harlequin ladybird survey website
- UK ladybird survey website
- Press release "The Ladybird Has Landed" by Michael Majerus
The Harlequin Ladybird Survey is funded by Defra, through the National Biodiversity Network Trust; the Biological Records Centre, CEH, Monks Wood; Cambridge University; and Anglia Polytechnic University.