A couple of weeks ago I was sat in the weak spring sunlight watching a beautiful red ladybird with a multitude of perfectly formed black dots scattered in a beautiful symmetry across its wing cases. It crawled along my foot, meandering in a seemingly drunken path back and forth; it was mesmerising to watch.
That is until it bit me…. you didn’t misread that, it definitely nipped me!
The thing is the ladybirds in my house are a bit of nuisance. As soon as the weather gets cold the corners of the rooms in my house fill with large numbers of them; they periodically go a bit mental and fly around my room. In fact, as I write a couple of repeatedly throwing themselves into the light in my room like light-drunk moths, and one is crawling over my computer mouse.
I do not know for sure, but I think these home invaders are harlequin ladybirds. These little beasties have been described as “one of the fastest spreading non-native species in Europe, as well as the most invasive ladybird on Earth”. They were initially introduced as a biological control, but their rapid spread means that they are now classed as an invasive species; they have the potential to disrupt the intricate and delicately balanced ecosystems around us.
So how are we going to combat the effects of this potentially devastating species? Well, when I was describing my ladybird-bite-ordeal to a friend, she mentioned that her friend, Emma Rhule, was doing a PhD giving harlequin ladybirds STDs… umm what!? I had to find out more!
Emma Rhule: Quite a few people have mentioned to me that they have Harlequin infestations at the moment. I think this is probably because they have been hibernating in the cracks of window sills etc and as the days get longer and it starts to warm up they will become more active.
Lizzie: So how much of a problem is/could the harlequin ladybird for UK ecology?
Emma: A voracious generalist, it has been estimated the arrival of the harlequin ladybird could negatively impact up to 1000 species (M Majerus, The Independent 2007). This is due to a number of factors. Firstly, the harlequin will consume its main prey, aphids, in large quantities, often outcompeting out native ladybirds and other species, such as lacewings and hoverflies. Secondly, the harlequin is not particularly fussy about what it eats; ladybird eggs and larvae (even individuals of its own species), the eggs and larvae of moths and butterflies and other [species] as well as non-target aphid species. The reduction in number of these species then has cascading effects on their predators, parasite and pathogens. Hence the 1000 species estimate.
From another perspective, the harlequin also has a number of negative impacts on humans. These range from the irritation of them invading our homes to overwinter, flying around when we turn the heating on and staining soft furnishing to allergic reactions from their bites
Lizzie: I was told that you give STDs to harlequin ladybirds – what exactly are you doing?!
Emma: One of the key theories to be introduced to invasion biology over the last decade has been The Enemy Escape Hypothesis. This posits that in the native environment, populations are controlled by the coevolved predators, parasites and pathogens that they encounter. When an organism invades a new habitat, it escapes these enemies and the pressures that they exert.
My work is looking to [introduce] a natural enemy that would specifically target the harlequin. Specific to ladybirds, Coccipolipus hippodamiae is a sexually transmitted ectoparasite that induces sterility in female hosts. I have been working on whether or not the parasite can use the harlequin as novel host and once populations are established, whether or not the presence of the mite induces sterility in female harlequins.
Lizzie: How do you describe your research when you meet people for the first time?!
Emma: Firstly, people tend to express surprise that ladybirds get STDs in the first place. Almost all promiscuous species have STDs and ladybirds rank fairly high on the promiscuity scale. They mate with multiple partners and each mating event can last in excess of eight hours!
Lizzie: I’ve read that the harlequin ladybird was originally a biological control, could what you’re doing be described as a biological control for a biological control?
Emma: The description of C. hippodamiae as a ‘biocontrol for a biocontrol’, that is exactly how I have described the potential use of the mite. Understandably, many people are a little wary about the idea of developing a biocontrol agent for a species that was itself developed as a biocontrol. This concern not only affects the work that I do but is reflective of a general distrust of biocontrol industry as a whole.
Lizzie: I read on your research webpage that the mite also affects the native species of ladybirds. Is there any way of assess whether this control will become a problem in its own right?
Emma: [The mite naturally] occurs in European populations of a number of species that are native to the UK. Obviously, this poses the risk that if released, the mite could go on to infect non-target ladybirds – populations that are already vulnerable since the arrival of the harlequin. Because of this, I am currently conducting an experiment to quantify the risk to each of our native species.
Few [native] British species of ladybird live long enough to overlap with the next generation, which means that any infections die out with them before horizontal transmission can occur. The harlequin, in keeping with its bigger, better, faster reputation is currently the only ladybird species in population that exhibits overlapping generations – in fact, records from The Harlequin Ladybird Survey suggest that the harlequin has two – three generations each year. This makes it an ideal candidate population for an STD. It also means that if the mite were to host switch into another ladybird species, then it would die out with that generation.
Many thanks to Emma for answering my questions; it is certainly a fascinating area of research! In the meantime if you want to help combat the problem of harlequin ladybirds through monitoring their movements, visit the Harlequin Ladybird Survey website to find out more. To aid the plight of the nicer ladybirds in the UK you can find more information here.