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Britain is stalked by cannibal invaders – can you help stop the harlequin ladybird? Britain is stalked by cannibal invaders – can you help stop the harlequin ladybird?
(about 21 hours later)
There are almost 2,000 non-native species of ladybird in Britain and a small proportion of these threaten aspects of biodiversity, society and the economy, and are deemed invasive. One, the harlequin ladybird, Harmonia axyridis, has now been resident in Britain for 10 years and has just been declared the UK’s most invasive species. There are almost 2,000 non-native species in Britain and a small proportion of these threaten aspects of biodiversity, society and the economy, and are deemed invasive. One, the harlequin ladybird, Harmonia axyridis, has now been resident in Britain for 10 years and has just been declared the UK’s most invasive species.
Related: Harlequin ladybirds declared UK's fastest invading speciesRelated: Harlequin ladybirds declared UK's fastest invading species
The harlequin has helped us to better understand the process of invasions, enabled by tens of thousands of people across the UK who submit their sightings to the UK Ladybird Survey.The harlequin has helped us to better understand the process of invasions, enabled by tens of thousands of people across the UK who submit their sightings to the UK Ladybird Survey.
Why does it matter that the harlequin ladybird is now dominating, even displacing some of our native species? Britain has 26 types of large, colourful ladybird and another 20 or so small, dull-coloured members of the same family, the coccinellidae. “Large” is of, course a relative term, in this case meaning over 3mm in length. Why does it matter that the harlequin ladybird is now dominating, even displacing some of our native species? Britain has 26 types of large, colourful ladybird and another 20 or so small, dull-coloured members of the same family, the Coccinellidae. “Large” is of, course a relative term, in this case meaning over 3mm in length.
Many, like the seven-spot and two-spot ladybirds, primarily feed on aphids (the greenfly and blackfly that are seen as pests by farmers and gardeners). Some ladybird species feed on scale insects and others on mildews, while two of the British species are vegetarians. The harlequin ladybird prefers aphids, but is a very generalist feeder and may outcompete many of its counterparts for a variety of foods. Different ladybird species all play subtly different roles in their ecosystems, the mechanics of which are complex.Many, like the seven-spot and two-spot ladybirds, primarily feed on aphids (the greenfly and blackfly that are seen as pests by farmers and gardeners). Some ladybird species feed on scale insects and others on mildews, while two of the British species are vegetarians. The harlequin ladybird prefers aphids, but is a very generalist feeder and may outcompete many of its counterparts for a variety of foods. Different ladybird species all play subtly different roles in their ecosystems, the mechanics of which are complex.
It is intuitive to think that ecosystems may be weakened by a reduction in the number of species present and their relative abundances, but this is something we need to explore further. The harlequin ladybird has not caused the extinction of any species in Britain so far. But its dominance may disrupt the balance of some ecosystems through cascading effects as a consequence of changes in interactions between species.It is intuitive to think that ecosystems may be weakened by a reduction in the number of species present and their relative abundances, but this is something we need to explore further. The harlequin ladybird has not caused the extinction of any species in Britain so far. But its dominance may disrupt the balance of some ecosystems through cascading effects as a consequence of changes in interactions between species.
Such knock-on effects are hard to predict – and detect. We believe we should be concerned if several common species are largely displaced by one new arrival. In some areas this has started to happen, particularly in the case of small, native ladybirds such as the two-spot and 10-spot, which have very similar feeding and habitat preferences to the harlequin.Such knock-on effects are hard to predict – and detect. We believe we should be concerned if several common species are largely displaced by one new arrival. In some areas this has started to happen, particularly in the case of small, native ladybirds such as the two-spot and 10-spot, which have very similar feeding and habitat preferences to the harlequin.
Harlequins are also particularly prone to feeding on other ladybird species, particularly at the larval (juvenile) stage. While other ladybirds also do this to some extent, harlequins are better at it: the larvae are bigger and better defended than those of other species (except our largest native, the eyed ladybird). Harlequins usually win in such confrontations of larvae that take place in summer on the nettles and trees of our gardens. They are also highly cannibalistic, a strategy that may seem like a bad idea, but can substantially benefit the species in times of food shortage.Harlequins are also particularly prone to feeding on other ladybird species, particularly at the larval (juvenile) stage. While other ladybirds also do this to some extent, harlequins are better at it: the larvae are bigger and better defended than those of other species (except our largest native, the eyed ladybird). Harlequins usually win in such confrontations of larvae that take place in summer on the nettles and trees of our gardens. They are also highly cannibalistic, a strategy that may seem like a bad idea, but can substantially benefit the species in times of food shortage.
So what can readers do? We still have much to learn about the ecology of ladybirds and the best way that people can help is by submitting records of their ladybird sightings to the UK Ladybird Survey. This can be done via a website or the iRecord Ladybirds app, a fun and easy way of taking part. Through these records we build a better picture of the distribution of ladybirds, the habitats and plants that they live in and how they are doing over the long term. From the photographs and notes provided, we can even learn more about ladybird behaviours and interactions with other species including natural enemies: parasites, predators and diseases.So what can readers do? We still have much to learn about the ecology of ladybirds and the best way that people can help is by submitting records of their ladybird sightings to the UK Ladybird Survey. This can be done via a website or the iRecord Ladybirds app, a fun and easy way of taking part. Through these records we build a better picture of the distribution of ladybirds, the habitats and plants that they live in and how they are doing over the long term. From the photographs and notes provided, we can even learn more about ladybird behaviours and interactions with other species including natural enemies: parasites, predators and diseases.
Harlequins can be tricky to identify but they are quite large (6-8mm) with red-brown legs and quite a rounded and domed shape. Their colour patterns are highly variable, but many are orange with about 16 black spots. Others are black with four, or less commonly two, black spots and prominent white “false eye” markings at the front.Harlequins can be tricky to identify but they are quite large (6-8mm) with red-brown legs and quite a rounded and domed shape. Their colour patterns are highly variable, but many are orange with about 16 black spots. Others are black with four, or less commonly two, black spots and prominent white “false eye” markings at the front.
Harlequin ladybirds are not just a problem in the UK and have also invaded most of Europe and North and South America (and parts of Africa). The displacement of native species by a small number of highly successful invaders (a process known as biotic homogenisation) is considered a major conservation problem worldwide. While we know of nothing that can halt the spread of the harlequin, what we learn about it as a model species will help us to understand how such problems may be tackled in the future. For now, why not look in the garden and see which ladybird species you can find?Harlequin ladybirds are not just a problem in the UK and have also invaded most of Europe and North and South America (and parts of Africa). The displacement of native species by a small number of highly successful invaders (a process known as biotic homogenisation) is considered a major conservation problem worldwide. While we know of nothing that can halt the spread of the harlequin, what we learn about it as a model species will help us to understand how such problems may be tackled in the future. For now, why not look in the garden and see which ladybird species you can find?