Thursday, 11 October 2018

Argh! ...Ladybirds!?

It's a warm, still day in the first couple of weeks of October, time for... STD-ridden home-invading alien ladybirds migrating in from Asia!?

Despite the utter drivel vomited up by a range of local and national newspapers this week (e.g. the Sun), ladybirds are not going to come for you this week. They aren't coming from Asia, they're not all black, they are physically incapable of stinging, and being bitten by one consists of a barely noticeable pinching that doesn't break the skin.

These are Harlequin ladybirds, Harmonia axyridis.  Imported into America and Continental Europe as aphid biocontrol, they were never officially released here, but turned up as accidental imports on flowers, fruit and vegetables as well as flying the Channel when the wind was in the right direction.  Like all other ladybirds, they overwinter as adults, and now that the nights are drawing in they are beginning to look for places to sleep away the winter. For Harlequins, this generally means houses.  This, combined with the fact that they like to overwinter in big groups, makes them far more visible than our native ladybird species, which mostly disperse into leaf litter in small groups or individually.

Harlequins quietly gathering in the corner of a window. Terrifying.
 The middle weeks of October are usually the peak time for records coming into the UK Ladybird Survey, and this year the weather has been warm and still - ideal for the Harlequins to gather into large swarms and seek out overwintering sites. They preferentially seek out sites which stand out from the background - pale buildings on top of hills, or at the edges of fields often seem to be favourites - and work their way indoors through open windows, lofts, cracks, and air bricks.

They are, of course, completely harmless. No ladybird is capable of stinging: they simply Do. Not. Have. Stings. Occasionally a particularly hungry individual may try to bite a person: as their jaws are too small and weak to break skin, this is at worst felt as a brief pinch before the ladybird gives up on you as inedible.  There are occasionally stories in the tabloids about people suffering terrible wounds from ladybird bites: these are nonsense.  Like the ridiculous spider-bite stories that have regrettably become a staple of red-top slow news days, all they prove is that any break in the skin is a possible window for infection.

Ah yes, infection.  Apparently these 'foreign invaders' are 'riddled with STDs', in turn causing a tide of people commenting on social media 'Who has sex with ladybirds hur hur'.  This is, again, stretching the truth to breaking point... and it's slightly my fault.  The best part of a decade ago, I found a Harlequin ladybird with tiny yellow finger-like growths on it - the first British record of a Harlequin infected with the fungus Hesperomyces virescens, one of the Laboulbeniales group.  We published the record in 2013 and a friend decided to do some work on it during her PhD: she put out a call for sightings, a newspaper misinterpreted it, and the rest is history.

Finger-like growths of Hesperomyces virescens on a Harlequin (photo c. Katie Murray)
The fungus isn't really an STD - it's a surface-living disease which is spread between individuals by close contact. It's also pretty much harmless - it potentially causes a slight lowering of egg production but not much else. When you combine those two facts, it becomes clear that Hesperomyces is pretty much the ladybird equivalent of athlete's foot or ringworm - not ideal, but hardly a major threat.  It (should) barely need pointing out, but being able to grow on the outside of a ladybird and on human skin are totally different abilities. YOU WILL NOT CATCH AN STD FROM A LADYBIRD.

Although they are native to temperate regions of Asia, they do not migrate from there to here. The Harlequin was first found in Britain in 2003, establishing in 2004, and all the swarms are of ladybirds born and bred here.  Once indoors, they'll generally set up shop somewhere cool - the top corner of a window frame is the classic site - and sleep the winter away until waking up in April. Because houses are warm, they'll sometimes wake up in mid-winter and fly round the light.  If they use up too much energy doing that, individuals will start dying and dropping to the floor after Christmas.  Like all ladybirds, when disturbed they can produce a yellow fluid ('reflex blood') that tastes horrible and this can sometimes stain soft furnishings.  If you need to get them gone, the key is to be either quick (scrape them into a pot and take it outside) or gentle to avoid this.

Obviously they aren't all black.  Their colouring is controlled by several genes so they come in a huge range of different colour forms (up to 109, though most are lumped together nowadays and several have never been found in Britain).  Some of these are black - about 20% of the UK population are black with two or four red spots - but most are orange with 0-21 black spots. The orange can vary from pale yellow to deep red-brown, and the spots from barely-there (or not present at all!) to massive blotches overlapping neighboring spots.  They're tricky to identify because they're so variable (they can resemble most of our common native ladybird species!) but the large size (5-8.5mm long), brown legs, and two-tone underside, combined with a usual 'M' pattern on top of the thorax makes them distinguishable.

Some of the many different colour forms of the Harlequin ladybird
The distinctive two-tone underside and brown legs of a Harlequin ladybird
If you've read this far - thanks!  To find out more about ladybirds, don't read the newspapers, for God's sake.  Next month the Field Guide to Ladybirds comes out (written by experts Helen Roy & Pete Brown, beautifully illustrated by Richard Lewington) and next May it will be followed by my own Spotlight: Ladybirds book - less shouty than this (no caps-lock text about STD misconceptions at all, you'll be sad to hear) but hopefully entertaining and informative with actual facts. I personally find facts so much more satisfying than lies and downright misinformation.

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