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- Herausgeber: Icon Books
- Kategorie: Lebensstil
- Sprache: Englisch
What is the best way to kill weeds in paving? How scared should we really be of Japanese knotweed? And what is a weed anyway? Biologist Ken Thompson set out to write a different kind of gardening column, one that tackles what he calls 'the grit in the gardening oyster'. In this new collection he takes a look at some of the questions faced by gardeners everywhere in a bid to sort the truth from the wishful thinking. Why are the beaks of British great tits getting longer? Which common garden insect owns a set of metal-tipped running spikes? Why might growing orange petunias land you in hot water? Are foxes getting bigger? How do you stop the needles falling off your Christmas tree? This expert's miscellany of (mostly) scientifically-tested garden lore will make you look at your garden through fresh eyes.
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PRAISE FORTHE SCEPTICAL GARDENER
‘A delight … if you have simply had enough of people refusing to take gardening seriously, I suggest you buy The Sceptical Gardener’
The Spectator
‘Packed with good, common-sense gardening advice gleaned from years of tending his own patch, it’s also very funny’
Waitrose Weekend
v
CONTENTS
ABOUT THE AUTHOR
Ken Thompson was for 25 years a lecturer in the Department of Animal and Plant Sciences at the University of Sheffield. He recently retired and moved to Devon, and writes regularly on gardening for the Daily Telegraph. His book, Where Do Camels Belong? (Profile, 2014), was described as ‘lively and punchy’ by the Sunday Times, and the predecessor to this volume, The Sceptical Gardener (Icon, 2015), was hailed as ‘a delight’ by The Spectator. In 2016 he was awarded the Royal Horticultural Society’s Veitch Memorial Medal for his contribution to the advancement and improvement of the science and practice of horticulture.
INTRODUCTION
Sport goes on and on, you see. You have to run on the spot to keep up. Events just keep on coming: moreover they keep coming in exactly the same order, year after year, which is sensible, but also a bit depressing if the sporting calendar’s rigid cycle dictates your actual life.
Lynne Truss in Get Her Off The Pitch! How Sport Took Over My Life
In the above quote, Truss is explaining why, after four years, she had had enough of being a sports correspondent for The Times. I’m sure she’s right about sport, but gardening, if anything, is even worse. At least when Spurs play Chelsea this year, the result may be different from last year; the exact score is almost certain to be. But it’s hard to persuade yourself that planting your runner beans or pruning your wisteria this year will feel much different from the same job last year. And gardening journalism can feel the same; once you’ve written one column on ‘what to do in June’, do you ever need to write another one?
Thus it was, ten years ago, that I set out to write a different kind of gardening column. One that addressed questions with no obvious answer – or worse still, answers xivthat are all too obvious, but still turn out to be wrong. One that asked questions that no one in their right mind had even bothered to ask before, such as whether birds understand speed limits, whether foxes really are getting bigger, what (if anything) the plants on the Duchess of Sussex’s new coat of arms tell us, and just what are ‘plants’ anyway? Occasionally, I even write something useful, such as how to make your own slug gel, the best way to stop the needles falling off your Christmas tree, or the best plants to persuade someone to buy your house.
My indispensable partner in this enterprise was, and still is, Joanna Fortnam, gardening editor of The Daily Telegraph. Joanna and I, despite actually meeting only rarely, manage to see eye to eye on the need for a column like mine – grit in the gardening oyster. Remarkably, ten years on, there still seems to be an inexhaustible supply of fresh stuff to ramble on about, and even more remarkably, neither Joanna nor the readers of the Telegraph seem to have tired of those ramblings.
After about five years, the columns available at the time were collected in the book The Sceptical Gardener. And now, in what seems like no time at all, here we are again, with a completely fresh collection. As before, I have not attempted to update them. Most don’t need it, and in any case the updating itself would soon be out of date. Here and there, I have added a brief footnote that explains where we are xvnow (in late 2019). In even fewer cases, a footnote clarifies a topical reference that isn’t obvious from the context. Otherwise, the columns are reproduced here in exactly the form in which they were originally written. A handful of columns failed, for one reason or another, to appear in the Telegraph (Joanna and I don’t agree about everything), but it seems a shame to waste them (especially as one or two are personal favourites), so they’re here too.
A huge thank you to Joanna, of course, for putting up with me all this time. And also to Duncan Heath at Icon Books, who not only took a chance on publishing the first collection, but was happy to come back for more. To everyone else at Icon, including Ellen Conlon for her work on the text, Marie Doherty for her typesetting, Lisa Horton for her lovely cover design, and Ruth Killick for publicity, and to Michael Stenz at the Telegraph, for seeing the project through to fruition. Many thanks as always to my wife Pat for putting up with me while I write. Finally, thanks to you, the reader. If these columns are new to you, I hope you like them, and if you’ve read them before, I hope you enjoy them all over again. I certainly enjoyed writing them.xvi
NAMES OF THINGS, MAINLY PLANTS
2
The fritillary’s chequered past
Reading a magazine article recently, I was surprised to find ‘marsh fritillary’ included among a list of plants. I suppose if you were a plant person, familiar with the common snake’s head and other fritillaries of the botanical sort, you might easily assume a marsh fritillary was a plant. In fact, of course, the marsh fritillary is a butterfly, and there are several other fritillary butterflies. Which set me wondering: why are the plants and the butterflies both called fritillaries?
The first thing to notice is that the butterflies and the snake’s head fritillary (but not most other plant fritillaries) share a rather similar chequered pattern, black and orange in the butterflies and various shades of purple in the plant. There is a general consensus, shared by Wikipedia and my Shorter Oxford Dictionary, that the name refers to this pattern, and comes from the Latin fritillus, meaning dice-box. But what exactly is a fritillus, and what has it got to do with a chequered pattern?
Well, the Romans were great gamblers, and went to a lot of trouble to prevent players cheating when throwing dice. The simplest solution was the fritillus, which was more of a dice-cup than a dice-box – usually a fairly plain cylindrical container in which dice were shaken before being thrown. Often they had ridges or grooves on the inside to help to agitate the dice and further prevent any attempt to interfere with a fair throw.3
But this is where things get complicated, because we have several fritilli recovered from Roman sites, and there’s nothing remotely chequered about any of them. Maybe the answer is the pyrgus, or dice tower, the ultimate anti-cheating device. A pyrgus, which removed the human element entirely, was a square tower, open at the top. Dice are thrown into the top and descend past a series of baffles, eventually leaving the tower at the bottom, tumbling down a short staircase which mixes them up even more. As long as the dice are fair, the pyrgus completely prevents cheating.
OK, you’re thinking, so what? Well, the dice tower had perforated lattice-work sides, probably to allow the players to see the dice inside, and make sure that the dice that left at the bottom were the same as the ones that went in the top. Overkill, you may think, but it looks like the Romans really did have a big problem with people cheating at dice. Crucially, this lattice pattern looks a bit like the chequered pattern of a fritillary, so maybe – just maybe – this is where the name comes from.
But then again, maybe not. In his book Flora Britannica, Richard Mabey prefers the account in John Gerard’s famous Herball, or Generall Historie of Plantes, first published in 1597. According to Gerard, ‘it hath beene called Fritillaria, of the table or boord upon which men play at Chesse, which square checkers the floure doth very much resemble’. Which certainly seems more straightforward than the 4tortuous dice-box story, although I should warn you that other theories are available; a variation on the fritillus story says that fritillary flowers resemble the shape of a fritillus.
We’ll probably never know the truth for certain, although I like the Gerard story. Either way, the snake’s head fritillary is both attractive and easy to grow, and will happily naturalise in a patch of damp grass. Beware the scarlet lily beetle, which likes to eat fritillaries, although the snake’s head is usually just a bit too early to suffer any serious damage. But if you want to see a fritillary butterfly, you will have to make a special effort; the urban gardeners among you are unlikely to see any of our eight native species in your garden.
DNA opens a can of worms for gardeners
Whatever Marie Kondo* may have to say on the subject (and frankly, who cares?), the arrival of a new book in the Thompson household is always a cause for celebration. 5Especially when it’s the fourth edition of Clive Stace’s New Flora of the British Isles.
Let me explain. For every generation, there’s a standard British Flora; the book whose mission, in the words of the first edition, is simply to enable botanists to identify the plants found growing in the wild in the British Isles. Since 1991, that book has been what is universally referred to as ‘Stace’. Pre-Stace, British Floras tended to be a bit sniffy about introduced plants, but Stace changed all that. Recognising that you often couldn’t know whether an unknown plant was native or alien, or whether someone had planted it or not, the pragmatic approach was to include everything you might expect to find in the wild. And since the source of new wild plants in Britain, more important than all the others combined, is horticulture, Stace is a useful guide to garden plants too.
For Flora writers, and for botany in general, the seismic shift came between editions two and three. Previously, our ideas about how plants are related to each other had been based mostly on morphology, but plant classification has been revolutionised by molecular data, especially DNA. The third edition of Stace was the first to reflect that revolution. But the changes were far from complete, and in fact they still aren’t, so although Stace’s approach is essentially a conservative one, the new edition includes many new changes that are now clearly here to stay.6
For gardeners, some of these changes are uncomfortable, to say the least. We already knew that Hebe had vanished into Veronica, and that most asters now belong in Symphyotrichum, but some changes go further than that. Sometimes, the genera created or altered by DNA information are morphologically indistinguishable.
To appreciate the true horror of that, you need to know that at the core of any Flora is a huge number of dichotomous keys, which lead you (with luck) via pairs of choices to the right name for the plant in front of you. Right at the start, a whopping great key takes you to a family. Once you’re in the right family, another key takes you to a genus, and then a final one takes you to a species.
When the whole system was based on morphology, that worked a treat, and mostly it still does. But consider the fate of Sedum. Ever since Linnaeus, Sedum has always looked like a large group of species that are obviously closely related to each other. But, says the DNA, they’re not. Old favourite Sedum spectabile is now Hylotelephium spectabile, and even two plants as similar as S. spurium and S. rupestre are now in different genera: Phedimus spurius and Petrosedum rupestre. As a result, Stace has abandoned a key to Sedum, and instead has a combined key to Sedum and the other three genera. Taxonomists don’t like having to do this, but there really is no other option.
Sometimes, the problem arises in reverse: plants that 7surely must be different but aren’t. The DNA says that Mahonia and Berberis belong together, but don’t panic; fearing a riot down at the garden centre, the taxonomists are doing everything they can to keep them apart.
Will the real laurel please stand up?
A while ago I came across a short article in a gardening magazine about laurels. It talked about Portuguese laurel (Prunus lusitanica) and spotted laurel (Aucuba japonica), but had most to say about cherry laurel (Prunus laurocerasus), which it described as ‘the true laurel’.
My Shorter Oxford Dictionary defines a laurel as (among other things) both ‘a tree or shrub of the genus Laurus (family Lauraceae), especially the bay tree, Laurus nobilis’ (and, separately, as any member of the Lauraceae) and ‘any of various trees and shrubs having leaves resembling those of the bay tree’. Which illustrates the problem; the word ‘laurel’ is being asked to do too much. On the one hand, it’s shorthand for the bay tree, or any member of the genus Laurus, or indeed of the family Lauraceae. On the other hand, it’s a useful name for any laurel-like tree or shrub, which essentially means anything with leathery, entire, evergreen leaves.8
That second definition is very broad indeed, and can include several evergreen cherries and the spotted laurel (as above), plus spurge laurel (Daphne laureola), Alexandrian laurel (Danae racemosa), Chilean laurel (Laurelia sempervirens), two American oaks (Quercus hemisphaerica, Q. laurifolia), and no doubt others. Naturally the cherries are related to each other, but all the other laurels are completely unrelated, to each other or to Laurus. On top of that, there’s the rest of the Lauraceae, including sassafras, cinnamon, avocado and Lindera which, unusually for a laurel, is deciduous and is grown mostly for its excellent autumn colour. The wonderful Californian laurel or headache tree (Umbellularia californica) has aromatic leaves, a bit like bay but even stronger – I never was quite sure whether the smell was supposed to give you a headache, or cure it. A very fine specimen in Sheffield Botanical Gardens blew down in a storm a few years ago, and is sadly missed.
In Ancient Greece, wreaths of bay laurel leaves were used to crown the victors of athletic competitions in the ancient Olympic games. Julius Caesar and Napoleon Bonaparte both understood the symbolism of the laurel wreath and liked to be pictured wearing one. And in modern times the laurel wreath lives on, even if only symbolically, in words like ‘Baccalaureate’ and ‘Laureate’.
So where does that leave the ‘true laurel’? On both botanical and historical grounds, I’d say that accolade 9belongs to the bay laurel. And I know I’m just prejudiced, but I would also say that the bay laurel is a better plant from a purely gardening perspective, as long as you can put up with its suckering habit. Cherry laurel is a thug, and spotted laurel is just plug ugly, although Portuguese laurel is a more refined shrub that deserves to be more widely grown. And spurge laurel is a lovely native plant for a shady spot, producing its inconspicuous and pleasantly (if faintly) scented flowers at a time of year when there’s not much else to look at in the garden.
On the other hand, it’s not my job (or anyone else’s) to police the use of the word laurel, so if you agree with the author of my original article that cherry laurel is the ‘true laurel’, no one is going to stop you. But the next time anyone tells you they’ve planted a laurel (or even a true laurel), you’re entitled to raise a questioning eyebrow.
Time’s up for rosemary
As we learn more about the family relationships of plants, chiefly these days by looking directly at their DNA, we often find that our earlier ideas weren’t quite right. One outcome is that plants’ names need to change.10
Mostly this means one of two things. One possibility is that we need new names. For example, the sprawling empire that was once Aster has nearly all vanished into new genera, and most of our garden Michaelmas daisies are now in Symphyotrichum. That had to happen, and my only complaint is that they could have chosen something easier to both say and spell. Something very similar has also happened to Sedum. This process is far from complete, so for example Sorbus (whitebeams and rowans) is currently on death row, and survives in its present form only because no one can decide what to do with it.
The second common outcome is the loss of familiar names, usually because one genus is found to be embedded within another, for example Hebe turns out to be entirely surrounded by Veronica. Leaving things like that would mean there were speedwells that were more closely related to hebes than they were to other speedwells, which is not allowed, so Hebe had to go. Lavatera, Nectaroscordum, Saintpaulia, Chionodoxa and many others have gone the same way.
The latest high-profile casualty is rosemary, which nicely illustrates the difficult decisions thrown up by the DNA evidence. There was always a good argument, purely on morphological grounds, for including Rosmarinus in Salvia, and the latest DNA evidence confirms that that’s where it belongs. So far so good, but what to actually do 11about that isn’t necessarily obvious. It may sometimes look like the botanists are out to confuse gardeners, but in reality they strive to make as few changes as possible, consistent with the scientific evidence.
In the present case, rosemary is in a branch of the Salvia family tree along with several other familiar salvias, including Salvia officinalis and S. sclarea. If you really wanted to, you could keep Rosmarinus, and those salvias, exactly as they are, but only at the cost of a version of the hebe/veronica problem: salvias more closely related to rosemary than they are to each other (definitely not allowed). And the only way out of that problem would be to invent a whole load of new genera for all the other salvias, such as the lovely S. patens and hundreds of others. Faced with the inevitability of upsetting an applecart, the botanists decided to upset a small one (Rosmarinus) rather than a large one (Salvia), a decision which I’m sure we can all applaud.
So rosemary is now Salvia rosmarinus, and we – and the manufacturers of plastic plant labels – are just going to have to get used to it. Of course, you can still call it rosemary, just as you can still grow hebes and asters, even if the plants are no longer in those genera.
Oh, I nearly forgot, exactly the same fate has befallen Perovskia, so P. atriplicifolia is now Salvia yangii. Why not Salvia atriplicifolia? Don’t ask – that would be a whole other column, and a very dull one.12
Better than wrong
Some time ago, I read some sensible advice on managing self-seeding garden plants, warning that although allowing self-seeders to grow is a great source of free plants, it can be problematic if you have weedy soil. Specifically: ‘You can’t take this laissez-faire attitude in a new or neglected garden, as the self-sown weeds choke the rest. Annuals such as groundsel, bittercress, bird’s-eye speedwell and sour thistle appear among the interesting, planted things, and the place becomes hard to keep on top of. But if your soil is relatively clean of weed seed after several years of regular tidy-ups, then what germinates in spring is usually desirable.’
Excellent advice, but what caught my eye was ‘sour thistle’. There’s no such plant, and it’s clearly a mis-hearing of ‘sow thistle’ (Sonchus oleraceus). On the other hand, sour thistle captures something that sow thistle doesn’t, and you almost wish Sonchus really was called sour thistle. Is there, I wondered, a name for such things, i.e. mis-hearings that are at least as good as the original, and maybe even better? Before the internet, I might have gone on wondering, but Google answered my question right away. There is such a word, and it’s far from new, with an interesting history.13
In an essay in Harper’s Magazine in 1954, American writer Sylvia Wright recalled how, as a young girl, she misheard a line from the 17th-century ballad ‘The Bonnie Earl o’ Moray’:
Ye Highlands and ye Lowlands,
Oh, where hae ye been?
They hae slain the Earl o’ Moray,
And laid him on the green.
She heard the last line as ‘And Lady Mondegreen’, liking the romantic image of the stricken Earl and the beautiful Lady Mondegreen dying in each other’s arms. Thus was the word ‘mondegreen’ coined by Wright for a mistake that’s better than the original.
A fertile source of mondegreens is song lyrics, which are often indistinct, and sometimes apparently meaningless even if you can hear them. I’ve spent my entire adult life believing that in ‘Purple Haze’, Jimi Hendrix sang ‘’Scuse me while I kiss this guy’, while all printed versions of the lyrics plainly say ‘’Scuse me while I kiss the sky’. In my defence, I was far from alone in the mistake, and Hendrix acknowledged the frequent mis-hearing by often deliberately singing the ‘mondegreen’ version in concert.
Sometimes, the mondegreen eventually becomes the correct version. The original version of ‘Twelve Days of 14Christmas’ has ‘four colly birds’, from the Old English col, meaning an ember or charred remnant, and thus meaning black, and eventually giving us the word coal. So the four colly birds are blackbirds. But sometime around the turn of the 20th century, colly fell out of use and they became calling birds, which is now the lyric of the official version.
But one of my favourite mondegreens is another plant. In his wonderful book Flora Britannica, Richard Mabey reports that the daughter of one contributor grew up believing that ivy-leaved toadflax (Cymbalaria muralis) was really called ‘I believe in toadflax’.
* The author of the bestseller The Life-Changing Magic of Tidying, who famously asserted that no one needs more than 30 books.
GARDEN WILDLIFE
16
Darwin meets the bird feeder
As I think I’ve mentioned before, bird feeding in British gardens takes place on a massive scale; the UK spends twice as much on bird seed as the rest of Europe put together. It would be surprising if this weren’t having some large effects, not least on the birds themselves. A recent study by a consortium of British and Dutch researchers, and published in the journal Science, sheds some interesting light on the subject.
One of the commonest species at bird feeders is the great tit, and measurements of hundreds of specimens from museums in Britain and mainland Europe show that British great tits have longer beaks. The difference isn’t enormous, but then neither are the beaks.
Of course, that in itself doesn’t tell us very much. There are no known differences in ecology and behaviour between British and European great tits, but maybe our tits have always had longer beaks for some unknown reason, or just by chance. So the authors looked at data from one of the best-studied bird populations in the world – the great tits of Wytham Wood near Oxford. Twenty-three years of data from Wytham’s birds show a steady increase in beak length. Again the change isn’t large, only about 0.1mm, but that’s a lot over such a short time, in an organ that only measured 13.5mm to start with.
But why are beaks getting longer in British great tits? The researchers found a gene, catchily named COL4A5, that 17was strongly linked to the change in beak length. They were then able to show that British birds with this gene successfully raised more fledglings, but that Dutch birds with the same gene did not. In fact, having the long-beak gene even seemed to be a slight disadvantage for Dutch birds. Notably, the greater success of the British birds wasn’t because they laid more eggs, they were just more successful at turning eggs into fledgling birds. Which in turn suggests that longer-beaked birds may be managing to obtain more food.
Back to Wytham, where data from radio-tagged birds showed that the genetically-distinct, longer-beaked birds were more likely to use bird feeders. In other words, it looks like birds with the long-beak gene may somehow be able to get more out of bird feeders. But the researchers don’t speculate about exactly how this might happen, so although the link between beak length and bird feeders looks plausible enough, more work is needed to figure out exactly what is going on. If our favourite theory turns out to be wrong, it wouldn’t be the first time. Personally, given the recent news about admissions to Oxbridge, I wonder if having longer beaks doesn’t just make it easier for Oxford’s great tits to look down their noses at other birds.*
18A footnote to this research is that the researchers identified a number of other genes connected to beak length, two of which are also linked to variation in beak shape in Darwin’s finches, nicely connecting this example of natural selection right back to the origin of the concept. I also can’t help noting that the Science paper reporting all this is entitled ‘Recent natural selection causes adaptive evolution of an avian polygenic trait’, a title that might have been designed to conceal this fascinating stuff from all but the most inquisitive reader.
Thumbs down for neonicotinoids
Neonicotinoids are systemic insecticides that inevitably find their way into pollen and nectar, and are thus consumed by bees, albeit in very low doses. You could be forgiven for thinking that the argument about whether this does the bees any harm would never end. Some experiments say it does, others say it doesn’t, giving encouragement to both sides of the debate. But one thing is for sure: almost all previous studies have taken place under some kind of artificial conditions, rather than in the real agricultural world. 19
The manufacturers of neonicotinoids have always maintained that this lack of realism exaggerates the negative effects of neonicotinoids, and that in normal use they are safe. So, full marks to Syngenta Ltd and Bayer CropScience for putting their money where their mouth is and funding a massive new study, although by now they must be wishing they hadn’t bothered.
The research, published in the journal Science, took place in the UK, Hungary and Germany, and was carried out here by the Centre for Ecology and Hydrology. Oilseed rape was grown under standard agricultural conditions, with all the usual pesticides and fertilisers. The only difference was that some of the rape was treated with the neonicotinoids clothianidin or thiamethoxam, and a control was not. The researchers measured the impact on honeybee hives and on colonies of a common bumblebee and a common solitary bee.
The effect on honeybees was inconsistent: negative here and in Hungary, but not in Germany. For the other two bees, there was no obvious effect of the experimental treatment. But fortunately, the researchers had taken the precaution of measuring the amount of neonicotinoids accumulated in the nests, which revealed a clear effect: nests with more neonicotinoids performed worse. Even more alarmingly, residues in nests didn’t consist only of the clothianidin or thiamethoxam applied during the experiment; they also 20 found a third neonicotinoid, imidacloprid. Since all three chemicals have been the subject of an EU moratorium since 2013, this means imidacloprid at least can hang around in the environment for years, still causing harm to bees.
The chemical companies may now be regretting shelling out L2.7 million for the study, although Bayer are probably regretting it more, since the evidence suggests that imidacloprid and clothianidin, both made by Bayer, are more harmful than thiamethoxam, made by Syngenta. In fact Syngenta have welcomed the study as ‘a helpful contribution to the ongoing debate about pollinator health’. Bayer, on the other hand, have set about rubbishing the study, claiming it doesn’t show what the published paper says it does (but trust me, it does).
In the debate that led to the current EU moratorium, the British government tended to side with the chemical companies, but was eventually overruled. Following Brexit, it will be interesting to see if part of taking back control means regaining the freedom to continue poisoning our bees. This study should help to make sure it does not.
Hello again, crab spider
Move from Sheffield to Devon, as I did recently, and everything changes: rainfall, temperature and soil to mention only the most obvious. It may even be worth having another go with plants that I tried in Sheffield, and that turned out to be the horticultural equivalent of banging your head against a brick wall (Tropaeolum speciosum springs to mind). But one of the less apparent changes is the opportunity to renew my acquaintance with one of the garden’s more charismatic (but mostly overlooked) inhabitants: Misumenavatia, the common flower crab spider.
Crab spiders have found a way of finding and catching prey that is so neat, and at the same time so obvious, that you wonder why more spiders don’t do it. Many different kinds of spiders use silk to create a huge variety of sticky traps, snares and tripwires, some chase down their prey, and others have evolved remarkable jumping ability. But crab spiders do none of these things; they simply sit in flowers and wait for their food to come to them.
Which would be interesting enough, but Misumena has another interesting ability (I’m almost tempted to call it a ‘superpower’): it’s able to change colour. Not almost instantly, like a chameleon or a cuttlefish, but over a few days. Crab spiders’ default colour is white or cream, but they can change to almost any shade of yellow, and then 22 back to white again. The matching against a yellow flower background can be quite uncanny, rendering the spider all but invisible, at least to human eyes.
There has been a lot of argument about exactly why crab spiders do this. The first explanation likely to occur to you is that the spider is hiding from the bees, flies and butterflies it is hoping to catch. But spiders of all kinds are also a favourite food of birds, so maybe they are hiding from their own predators. Some fancy research, simulating how crab spiders might appear to both birds and bees, has left the question unresolved; they could be hiding from either – or both. But a complication is that they often don’t seem to be trying very hard. That is, if you collect crab spiders from a range of white and yellow flowers, they don’t seem to match where you collected them much better than by chance.
Fortunately, other observations can help us to discover what crab spiders are up to. One large study of the stomach contents of birds found the remains of over 10,000 spiders, of which just four were Misumena. So birds eat very few crab spiders. Of course, that could just mean that the crab spider’s camouflage is perfect. But no camouflage is that good, and you would expect birds to detect spiders moving between flowers, or while they were eating their (much more conspicuous) prey. Moreover, one researcher spent 30 years studying crab spiders without witnessing a 23 single bird attack. So it looks like birds don’t bother with crab spiders, but we don’t know why not.
At the same time, other researchers have been studying how well potential prey can detect crab spiders. Crab spiders are quite small, so they are more dangerous for smaller bee species. One study found that small bees tended to avoid patches of flowers with crab spiders, and to prefer spider-free patches. But how do the bees know the spiders are there? The answer is they don’t. Bees rapidly left flower patches infested with spiders, but only after experiencing a ‘close call’ (i.e. surviving an unsuccessful attack). So it looks like bees are unaware of crab spiders until they are attacked. Which all suggests that whatever else it may do, the crab spider’s camouflage is certainly very good at fooling insect pollinators.
