Dedication

Dedicated to my dad … you would have been chuffed to bits

Contents

Cover

Title Page

Dedication

Foreword by Chris Packham

Introduction

40 Mating natterjacks

39 Wood ant nests

38 Displaying glow-worms

37 Playing fox cubs

36 Trapping moths

35 Grey seals pupping

34 Winter high tide roost

33 Machair in summer

32 Wild goats rutting

31 Swallows and martins feeding

30 Otters fishing

29 Roosting rooks

28 Pipistrelle bats swarming

27 Clouds of butterflies

26 Terns attacking

25 Pine martens hunting

24 Roosting parakeets

23 Dancing cranes

22 Hunting peregrines

21 Spiders’ webs

20 Wheeling puffins

19 Autumnal trees and toadstools

18 Wild orchid displays

17 Whale watching

16 Courting great crested grebes

15 Leaping dolphins

14 Boxing hares

13 Sea eagles fishing

12 Rutting red deer

11 Flocking pink-footed geese

10 Barn owls hunting

9 Basking sharks feeding

8 Dancing adders

7 Bluebell displays

6 Dawn chorus

5 Meadows in summer

4 Lekking black grouse

3 Leaping salmon

2 Roosting starlings

1 Diving gannets

Index

Acknowledgements

Keep Reading

Copyright

About the Publisher

Foreword

by Chris Packham

I made my first list when I was about eight. I thought nothing of it; it seemed perfectly natural. I was obsessed with reptiles at the time, which seemed normal too, and I’d come down from the heady heights of the dinosaurs to the British Six, as my list was called. Adder, grass snake, smooth snake, sand lizard, common or viviparous lizard and slow worm were the words so neatly inscribed in my book, even if I didn’t know what viviparous meant and had to be careful spelling it. I had four out of six ticks alongside them, not bad thinking about it now, but seriously disappointing for the obsessive young naturalist who had to wait an eternity – until he was twelve – to put the final mark alongside sand lizard. Lying in bed that May night wrapped in the warmth of smug satisfaction, I then wondered if I could be the youngest person ever to see the all of the UK’s native reptiles.

Several things are revealed by this admission: that list-making is a very important part of any naturalist’s behaviour; that an incomplete list can cause real distress and lead to an increase in obsessive behaviour; and that lists have a strong competitive component. When you think about it, they are only made to be completed. Shopping lists, wedding lists, they are all made up of things that we need, and the difference between want and need is a notable one. So, listing things is sometimes helpful but patently questionable, and I’m not sure that it makes you particularly happy sometimes, either. But I am certain that it gets you out of bed and that it can act as a wonderful fuel to get your life lived more fully. Oh, and people say that listing is geeky. So what? If you’ve picked up and paid for this book you are at least a little bit geeky, and that’s good; be proud of it!

It’s tempting to imagine that naturalists invented listing, but I’m sure it would be hotly contested from many sides. Historians are also consummate listers, and collectors of anything are listers par excellence, but I think we hold our own. I have a British bird list, a world bird list, a garden bird list, a dogwalking bird list, a garden moth list, a British butterfly and bat and amphibian list, an orchid list, a travel list … and, to be fair, that’s nothing. I’m an amateur when it comes to listing. But these are all empirical lists; there are also the subjective lists – and these are very exciting because they are dynamic and more interactive. We brag about the former, but we debate the latter.

My Top Ten Favourite Films Of All Time (the last bit is fabulously childish, but necessarily demonstrative, and should follow all such list titles) obviously bears no resemblance to the list from which I was trying so hard to tick smooth snakes and sand lizards, although Raquel Welch of the One Million Years BC era still features in several lists. And it can be thrown into turmoil by a single release; it can require a systematic reappraisal, taking hours and contentious ‘discussion’ with my movie guru James. And that is great, too, because opinionated lists must be argued about as a matter of honour. I mean, how can this self-appointed ‘guru’ have Blade II in his Top Ten? Or, more to the point, how the hell did black grouse lekking make it into the Top Five of this list when glow-worms are languishing in the 30s? And who seriously thought: it’s right that a spider’s web is not Top Ten material? And, to my mind, puffins should not be seen or heard in any list, gaudy little chavs. Starlings, swirling about going to roost, good, but so passé. That’s like still having The Italian Job in your Top Ten Movies. I mean, come on, update will you?

What is even more exciting about Nature’s Top 40 than the order is that it’s a UK-based list, and that it finally gives us a chance to bunch together a set of spectacles, which undeniably deserve their status, if not their final positions, in your or my opinion! It proves beyond doubt that the UK is not the land of ‘little brown jobs’, or ‘quite good for its seabird colonies’, or ‘has a few nice spots’; it is rich in things that can stop you in your tracks, make your heart miss a beat, make you hold your breath, make you travel a hundred miles, make you want to shout out loud, make you make lists of things it will make you do!

Joking aside – and I know that many of you will immediately count through to see how many of this 40 you have already seen – the actual ‘final’ positions don’t matter. What does is that you use this list to get you out to experience and enjoy these spectacles first-hand and that you get some youngsters out there with you. Ask yourself this: how many twelve year olds today have seen all the UK’s reptiles in the wild, or, more importantly, lie awake wanting to? If this list is to endure, we need some more of these apprentice listers, and that could be down to you.

Chris Packham

2008

PS The answer is … I’ve seen 37. I haven’t seen the roosting parakeets or the wild goats, and I would most like to get to grips with adders dancing.

Introduction

Music charts lend themselves to a list according to their popularity based on the solid statistics of sales volume, as do films, and of course computer games and books … but wildlife? Some may wonder how we dare make a Top 40 list of Britain’s greatest wildlife spectacles in such a manner, and may feel that the act of giving each of our chosen entries a number might even cheapen the very spectacle we have filmed and written about.

Others will be indignant that their favourite spectacle has unfairly been demoted to the lower regions of the Top 40. But look down any of the numerous Top 40 lists that have formed the basis of a variety of television programmes, such as the Funniest Moments on TV. Undoubtedly part of the fun is exclaiming in a faux-indignant way that the clip of talk-show host Russell Harty being attacked by Grace Jones is not as funny as the lower-ranked, but hilarious, moment where a slightly-worse for-wear Delia Smith screams, ‘Lets be having you!’ to a bemused Norwich City football crowd at half-time. There will also be those wildlife purists not best pleased that immigrant (and therefore ‘lesser’) spectacles, such as ‘parakeet roosts’ and ‘rutting goats’, have audaciously elbowed a spot in the list and now vie for attention alongside our native British spectacles. And, come to think of it, why are badgers playing and kingfishers fishing completely absent from the list altogether?

Our Top 40 was compiled from contributions by members of the public, following a request on the BBC Nature’s Calendar website for their suggestions. The 40 most popular suggestions put forward were then ‘moulded’ into an order by a panel of wildlife experts who argued (I believe well into the night) on the relative merits of each species and exactly why, for example, the thrilling clouds of butterflies, which was positioned at no. 27, deserved a higher spot than the enchanting light show put on by glow-worms at a more lowly number 38.

The factors taken into account when compiling this list included a combination of how unique the spectacle is to Britain, and a ‘thrill-ability factor’. Some of the entries in our ‘wildlife chart’ involve huge numbers of one species, such as pink-footed geese returning to roost, or bluebells flowering synchronously in a spring wood; others comprise either fewer or single individuals with particularly remarkable or fascinating behaviour, such as spiders building webs or great crested grebes courting. The best spectacles inevitably involved large numbers of one species (or a combination of species) acting in a remarkable manner, with Britain additionally being the best place in the world to view that event. The prime example of this is gannets diving, which deservedly made our number 1, because Britain holds an astonishing 63 per cent of the world population of gannets, and the very sight of flocks of these birds pelting into the water is frankly breathtaking.

It is important to bear in mind that these spectacles have not, of course, evolved for our viewing pleasure, and we are nothing more than voyeurs in what serve as vital functions in the mating and survival games of each of our entries. So, in addition to helping you find out more about how to come across each spectacle, the body of the book is primarily written to enable you to understand exactly what is going on and why, which should hopefully enhance your enjoyment and renew your appreciation of the wonderful wildlife still eminently viewable on and around the British Isles.

We make no apologies for the order of our Top 40; you may not agree with it but, hopefully, it may just occasionally form a stimulus for conversation in place of the latest TV series plotline. Perhaps you will be encouraged to make your own ‘Wildlife Hit Parade’. The primary motive behind the series and this book is, unashamedly, to encourage people to jump off their sofas, turn off their television sets and stow away the computer games console in order to get some fresh air in their lungs and a few spectacles under their belts instead.

Finally, with some insider information, the vast majority of these spectacles can be seen with a little planning and the requisite luck. Only when the joy or ‘Gospel of Wildlife Watching’ spreads to as many people as possible (irrespective of the order in which we place them), will these plants, the animals and their habitats be truly cherished, valued and conserved for future generations.

40 Mating natterjacks

The ‘Birkdale nightingale’, ‘Bootle organ’ and ‘Thursley thrush’ are all regularly used colloquial monikers that, in certain regions, have replaced the more commonly accepted name of our smallest and rarest British toad, the natterjack. The reason why such a seemingly inconspicuous and rare toad should been given so many local nicknames is purely down to its incredible ratchetlike call, which marks the highlight of its breeding season, and is also a tremendous spectacle for anybody with a penchant for toadspotting.

Natterjack toads

WHEN

April to mid-May

WHERE

Ainsdale NNR, Merseyside; Caerlaverock Nature Reserve (WWT), near Dumfries

‘Do not park here! The solid yellow line is the key identification feature of the natterjack toad.

David Woodfall

This diminutive relation of our common toad is entirely restricted to Europe, with its heartland being the Iberian Peninsula, and becoming progressively rarer further north. In Britain the natterjack was widely if locally distributed around southern and western coastal locations, but healthy populations can now only be found along the northwest English coast around Merseyside and in southwest Scotland centred on the Solway Firth.

To the untrained eye, natterjacks are similar to the common toad, but their size of no more than 75 millimetres, dry brownish to olive-green warty skin and yellow stripe, which runs the length of their backbone like a ‘no-parking here’ line, easily distinguishes this wonderful and mercurial little toad. In addition, natterjacks have short hindlimbs, giving them the ability to run at surprising speeds over short distances. Unlike common toads, where the females are generally larger, there is little difference in the size of the natterjack sexes, even when the females are bursting with eggs and ready to spawn.

Natterjacks in Britain are now found almost exclusively among sand dunes and the periphery of salt marsh close to our coastlines; they will always be below 100 metres above sea level. Befitting a species that is most abundant in Spain, it is no coincidence that this is one of the warmest habitats in Britain. These sandy spots are also perfect for a species that is a compulsive burrower, meaning that natterjack toads are easily able to dig down to escape from the extremes of temperature. The short, dense vegetation attracts lots of invertebrate prey, and, as sandy places are also well drained, natterjacks have evolved to breed in ephemeral freshwater pools and ponds in the dune slacks. A typical breeding site will often be no more than a small, sandy, shallow and unvegetated pool with a maximum depth of 30 to 50 centimetres that will often have completely dried out by the height of summer.

In common with all our native amphibians and reptiles, the natterjack is a species that opts out of the coldest autumn and winter months by hibernating. In the case of natterjacks, this time is spent underground in self-excavated burrows either alone or with other toads, with the largest number – an astonishing 44 – recorded by the celebrated herpetologist Trevor Beebee.

On good nights you might get the impression that you had dropped in at the Okavango delta or the Amazon basin at dusk rather than it being just a misty night on Merseyside!

After this period of torpor, the toads then emerge into the light in March or early April once the air temperatures have warmed up sufficiently to sunbathe.

Adults leaving their hibernacula, or winter residence, have usually only two things on their mind, and the first of these is food. The toads emerge to start foraging at dusk and may move several hundred metres from their burrow to feed in the dune slacks before returning to the same burrow before dawn. The natterjack is much more athletic than the common toad and hunts actively by running down its prey over short distances. The long sticky tongue then shoots out at lightning speed to ensnare the unfortunate ant, bug, beetle or fly. Smaller prey is swallowed immediately while larger prey often takes a while to gulp down and can be disposed of by the toad’s ingenious ability to retract its eyeballs back into its head, thereby applying pressure to the roof of the mouth and, hence, helping to crush and swallow the food.

While natterjacks will eat virtually anything that will fit into their mouths, the adults themselves have comparatively few predators due to the nature of their skin, as the larger warts contain parotid glands that secrete a poison when molested. This deters most predators, with the exception of some members of the crow family, which have learnt to disembowel them leaving the skin behind, and grass snakes, which seem less susceptible to the poisons. A secondary defence for the natterjack when faced with a grass snake is to puff itself out like a little balloon and stand high on all four legs to give the impression that it is larger and more menacing than it really is.

Having fed, the toads are then keen to move on to the details of mating. The first stage involves the short migration back from their winter quarters to the breeding site of choice and this generally occurs in late March or early April on evenings where the temperature is above 8°C. The males are the first to arrive at the pond and initially tend to occupy burrows close to the water. It is easy to tell when the breeding activity starts in earnest as the natterjack has the distinction of being Europe’s loudest amphibian and its calls can easily be heard from a mile away on a warm, still night. After sunset the males emerge from their burrows to take up evenly spaced positions in the pond margins. They then adopt a stance with their forelimbs straightened to keep their head and, more importantly, their vocal sac clear of the water.

The sight and sound of a male in full voice is an unforgettable experience. Its strident call is produced by an inhalation of air through a couple of slits in the bottom of the mouth, which is then shuttled backwards and forwards between the lungs and the vocal sac. This results in an enormous inflation of the vocal sac so the toad’s actual head becomes three times its normal size. As the normally purplish or bluish throat distends, in the light of a torch it appears ghostly white and translucent and is very reminiscent of a child’s bubblegum bubble. Normally, a male will be stimulated into calling by the churring of other surrounding males but even passing vehicles and planes can initiate a chorus. The call sounds like a ‘rrrrRIP’ that lasts for about a second before a slight upturn at the end, and individual males will usually call continuously for around a minute before taking a short rest and winding up again.

Calling males vastly outnumber the females on any given night, as the males may well stay for the entire breeding season, and a visitation by the female could be confined to just a few hours on one night of the year. As the ratio is skewed towards amorous males, much time is often wasted in chasing, grabbing and releasing other males in a case of mistaken identity. This error is soon sorted out by the grabbed male, who makes a small croak to let the other male know it is ‘riding the wrong chariot’; he is then immediately released. Females do not often arrive until after dark and are usually grabbed by the first males who chance upon them. In each case the male then proceeds to lie on the back of the female and keep hold by using his forelimbs to tightly clasp around her armpits in a grip called ‘amplexus’, which is strengthened by rough nuptial pads on the digits of the toad’s forelimbs.

This coupling process is a lot more gentlemanly than with common toads, where an unmated female can become covered by a writhing mass of males to the extent that she may even occasionally drown. With natterjacks, however, there seems little territorial behaviour or aggression, and, once a male has attached himself to a female, it seems often to be taken as read that the female is no longer available and the couple are left unmolested as the female selects a suitable shallow spot to begin spawning.

Most spawning takes place at night but can occasionally be seen in broad daylight after particularly busy nights. The egg-laying itself is a protracted process taking around three hours, with the female ejecting eggs in a long string, in between periods of rest; the male then fertilises these externally. The natterjack females will produce between 3,000 and 4,000 eggs in this way; the strings are easily distinguished from those of the common toad after a period of 24 hours, as the eggs develop into a single row as opposed to the double row of their common counterpart. As soon as the spawning is finished, the male swims away to look for more mating opportunities, while the female leaves the water, spent, her breeding season over and wanders off to feed.

During sunlight hours, natterjack tadpoles are visible in large numbers at the water’s surface or along the pond edges. This contrasts with frog tadpoles, which are much more shy and retiring. The tadpoles must grow quickly as they will all die if the pond dries out completely. Those that survive the high summer droughts and the jaws of predatory insects – the minority – metamorphosise, and head to the land and a brave new world in which they must fatten up in preparation for hibernation.

39 Wood ant nests

Ants are a subject to which many people have never given much thought, unless it is how to extinguish them when they invade our houses. The best thing to do, though, is to take a moment to watch ants, rather than exterminate them. There is much to be admired about an organism with levels of societal organisation that are the envy of the natural world.

Wood ants

WHEN

Most active from early spring through to late autumn

WHERE

In scattered woodlands and coniferous plantations throughout Britain; distributions depend on species. Coed y Brenin, near Dolgellay, Gwynedd; Glen Affric NNR (SNH), Inverness

A foraging party of wood ants. Something to stay well clear of if you are a juicy aphid.

Stephen Dalton

Britain’s ant fauna of around 50 species is impoverished when compared to the tropics; the famous biologist and ant expert EO Wilson once stated that he could find as many species of ant on one tree in the Peruvian Amazon as exist in the whole of the British Isles. However, what Britain lacks in quantity, it makes up for in quality, with the wood ants being among the most charismatic of this immediately recognisable, but little understood, group of insects.

Of the six possible species of wood ant in Britain, only three are commonly encountered. The Southern wood ant, the Northern hairy wood ant and the Scottish wood ant all look quite similar and are identified by the shape and amount of hair on their heads or, rather more easily, by geographical location, with the exception of a few places where two of these species will occasionally overlap. Moreover, none of these species will come anywhere near your larder!

With the largest individuals being around ten millimetres in length, wood ants are not only the biggest British ants, but they also have the most populous colonies, with some nests reaching close to half a million individuals. They are also the only true woodland ants in Britain, as all of our other native species need warmer temperatures and so are invariably found in more open and warmer habitats such as heathland or grassland. The ability of the wood ants to conserve heat in the cooler forest environment make them the ideal candidates for living in what might be considered an unsuitable habitat.

A large wood ant nest on an otherwise fairly bare forest floor is an impressive sight. These domes can easily reach to over two metres in height and are, moreover, only the above-ground part of the nest; the structure can extend at least as deep again underground. If one of these nests were to be sliced in half, it would reveal a citadel of complex interconnecting tunnels and galleries that would surpass even the wildest imagination of today’s science fiction writers.

During the summer months the surface of these nests can be a wriggling mass of thousands of ants busily carrying out their specific chores. The vast majority will be wingless workers, essentially immature females that take no part in reproduction. These differ in size between five and ten millimetres, according to the different jobs that have been preordained to carry out from the moment they emerge from their pupae. Some will spend their lives collecting honeydew – a saccharine substance found on the leaves of plants – or catching insect prey, while others will tend to the eggs, larvae and pupae, and a still different caste will have the responsibility of building and repairing the nest.

The sole egg-laying machine in the wood ants’ nest is the queen. She can usually be identified by her much larger thorax that houses the flight muscles, and an outsized abdomen, which contains the ovaries and a sperm sac from her single mating. Although the vast majority of her eggs will develop into the different worker castes, during spring, winged queens and males begin to emerge from slightly larger pupae. These ‘sexuals’ will take to the air and mate, after which the queens disperse to form new colonies away from the mother nest. Separate nests in the same wood are able to synchronise the release of their sexuals on the same day so that new populations have a shuffled combination of genes to avoid inbreeding. These synchronised flights of the winged wood ants will only occur during the right climatic conditions and the number produced can be vast as they rise into the canopy to mate on the wing or in the treetops. While many will be eaten, for example by insectivorous birds, the local predator population often becomes quickly swamped by this sudden surplus of food meaning that there is negligible overall impact.

An ant citadel, with a population slightly larger than Bristol and, arguably, far fewer traffic jams!

Laurie Campbell

After this mass aerial ant orgy, the males die and the females return to the ground, shed their now-obsolete wings and look for suitable nest sites. In the case of the Southern wood ant, the queen will track down a colony of a closely related species, the common black ant. She will then gather a few common black ant pupae and construct a special cell within the colony for them; upon hatching they will join their ‘stepmother’ in killing the original host queen. They will then look after the queen Southern wood ant’s eggs but, once the queen’s own eggs have hatched, the new Southern workers take over the colony and extinguish the original black ant colony!

The one and only mating from her nuptial flight will have provided the queen with enough sperm to last her entire life, which, in the case of wood ants, may be an astonishing fifteen years, during which time she may well lay hundreds of thousands of eggs. These eggs are placed in the warmest part of the nest until they hatch into hairless larvae. The larvae are then fed on a part-digested liquid meal by the workers, before they finally graduate on to prey items collected from the forest. As the larvae grow, they are meticulously looked after by the specialised workers while they undergo a number of moults until they are ready to pupate into either the workers or the sexuals.

Wood ants also use their incredible social organisation when, after a period of winter hibernation, the first few days of spring will be marked by an increase in activity and the workers can be seen pouring away from the nest along special pathways that they meticulously keep obstacle-free. In contrast to many ant species, which use chemical signals or pheromone trails to find their way, wood ants exploit their excellent eyesight; they use a combination of the shapes of the surrounding vegetation against the sky and the orientation of the sun. Foraging parties will then retrace their route back to the nest with their spoils.

Diligent ant researchers have extrapolated that, on a single warm summer’s day, a typical wood ant colony can bring back as many as 60,000 individual items to the nest; these include aphids, caterpillars, beetles, flies, harvestmen, woodlice and plant material. A daily haul of around 140 grams of solid food can have a serious impact on the wood, leading to so-called ‘green islands’ around nests, where the vast majority of the defoliating insects have been removed, meaning that the leaves remain virtually unblemished. A very important additional food source for wood ants is honeydew which is collected by the ants from aphids that have tapped into a plant’s sap. The wood ants will often protect their aphids from attack by ladybirds and, in return, effectively milk them, like we would our cows, for a reward of a tiny drop of sugar solution.

A substantial proportion of the daily items brought back will consist of leaves and twigs, or needles if the nest is under conifers, which will be used for running repairs to the nest. The nest is designed to keep out the rain, but is also constructed to catch heat to enable the ants to operate under conditions much warmer than that of the surrounding ambient air temperature. On the surface of the mound the temperature may vary by as much as 15°C in summer, but the heart of the nest can be kept at an incredibly constant and snug 25°C. Particularly in the first cold but sunny days of spring, it is thought that many ants will emerge to sunbathe before carrying the heat below to warm the nest.

The wood ant workers also have three formidable weapons to defend the nest against potential intruders and to subdue their insect prey. Like all ants they have relatively powerful jaws and huge supplies of formic acid, which can both repel borders and act as an alarm signal to the colony. Finally, the wood ants are able to rely on sheer numbers to help them overrun and subdue the enemy. If the surface of the nest is stirred up, large numbers of ants run to the disturbed point and curl their abdomens around to squirt the acid at the potential threat. Despite these defensive measures, significant numbers of ants will still often be consumed by green woodpeckers and badgers.

Away from the nest, territories may spread for close to 100 metres in all directions depending on the local competition. Ants can recognise colleagues from their own colony by a ‘nest odour’ and may viciously attack strangers; spring battles sometimes occur between some of the separate wood ant colonies as they delineate territories. Like all civilised societies, diplomacy will usually predominate if there is more than enough territory to go around, resulting in nests of many sizes and stages of maturity in favourable woods.

38 Displaying glow-worms

There can be few more delightful surprises for a naturalist than to walk along a country lane on a summer’s evening and to chance upon small pinpricks of luminous light emanating from the fields flanking the hedgerows. In addition to these unique biological lights being one of Britain’s most underrated wildlife spectacles, their function plays a vital part in the mating game of a fascinating insect.

Glow-worms

WHEN

Mid-June to mid-July

WHERE

More common in the south. Slapton Ley NNR, Devon; Barnack Hills & Holes NNR (Natural England), Cambridgshire; Aston Rowant Nature Reserve, near Stokenchurch, Buckinghamshire

The flightless female puts on one of nature’s finest light shows … and all to attract a male!

Stephen Dalton

The glow-worm is Britain’s only bioluminescent representative of an order of insects called fireflies, a group that reaches its maximum diversity in the tropics. However, both their name and the order to which they belong can be very confusing, as glow-worms are neither worms nor flies, but members of the order of beetles.

While those lucky enough to have seen this miniature version of the Blackpool lights are few, even fewer people realise that the light show is merely the final two per cent of the glow-worm’s intricate life cycle. For the previous 15 months, they have been quietly transforming from egg, to larva, to pupa and finally to adult as they prepare to go out in a blaze of colour.

In common with the vast majority of insects, the glow-worm starts life in the autumn as an egg. Batches of between 50 and 100 eggs are laid under vegetation or stones by a female from the preceding generation, a task so arduous that the exertion is her last task before she dies.

Each egg takes around 35 days to hatch, after which out pops a larva. The creature that emerges is a lean, mean, killing machine, and, once its skin has hardened, it has only one thing on its mind: food. The glow-worm larva is a specialist eater, restricting itself to a diet of snails and slugs, which are tracked down at night with its sensitive antennae and palps (feelers). Once potential food is located, the larva is able to tackle prey, such as snails, much larger and heavier than itself. It does this by giving the snail’s foot a series of nips with its sickle-shaped mandibles (or jaws). These mandibles are hollow and deliver a powerful poison, which firstly acts upon the snail’s nervous system to cause paralysis, and secondly starts to digest the snail into a ‘soup’ that is then lapped up by the larva.

During this process, the snail is paralysed but still alive; very occasionally, partly eaten snails have been known to recover as the toxin wears off and crawl away to fight another day. The larva is capable of eating substantial meals at one time meaning a rapid growth rate. However, this presents a problem as the growth occurs inside an inflexible exoskeleton. The larva solves this like many other immature insects, by undergoing a moult, in which the old skin is shed and replaced with a larger version.

Even though it is the adult females that are associated with the light show, the larva is also able to produce a faint light, which often pulsates on and off. The reasons for this are not entirely clear, but this technique is thought to be used to scare off potential predators. After a couple of moults and as winter takes hold, the larva becomes more lethargic and then hibernates under logs, stones or leaf litter. In the spring of their second year, the larva emerges hungrier than ever and eats voraciously over the spring and summer, undergoing moults along the way in preparation for breeding the following summer. Towards the end of the summer in their second year, as they curl up to see out their second winter before breeding, the much larger females can easily be identified from the males.

By the following spring, the larva is virtually full-grown and may not even need to moult again before it pupates. Once early summer arrives, the larva often loses its nocturnal habits as it actively searches for a suitable place to pupate. This is particularly important for the females: they are remarkably sedentary as adults so use this period to colonise new areas.

The larva then picks a secluded area and begins to pupate, a remarkable process in which the larva’s body, including all the organs, is completely broken down and then reconstituted as the adult form takes shape. This process takes just over a week for the females and slightly longer for the males as they have to undergo a more drastic alteration due to their need for the power of flight.

The first glowing females of the season are usually seen from mid-June, and, with their segmented bodies and absence of wings and wing cases, retain more than a passing resemblance to the larvae. The light organ is positioned on the underside of the abdomen and consists of two luminous bands and a couple of luminous spots set either side of the ovipositor, the organ from which the eggs will be deposited. The glow-worm’s light is produced by a string of chemical reactions between a small protein called luciferin and a large enzyme called luciferase. Though the complex reaction is still not totally understood, it is an incredibly efficient process: 98 per cent of the energy is released as light, compared to a measly 5 per cent in a light bulb, in which the vast majority of the energy is wasted as heat. This means that the light organs of the glowing females are completely cold to the touch.

Rough grassland with little light pollution is essential if you are a female glow-worm desperate for attention

David Woodfall

Andy Rouse

It is only virgin females that glow; once a female has mated and begins egg laying, the light organ has served its purpose and is switched off.

The glowing performance usually commences soon after dusk at around 10–10.30 p.m. It is thought the turning on of the light is triggered by a drop in light intensity below a certain threshold level, which explains why glow-worms that advertise in the darkness of a woodland edge will begin glowing earlier than populations in predominantly grassland locations. The female will generally display close to the ground, or up to a maximum height of around 40 to 50 centimetres if she feels a higher vantage point would be more beneficial. Females will even glow during rain, but usually stay closer to the ground during inclement weather.

Because the light organs are set on her underside, the female also has to twist her abdomen around to make sure that any males flying past will see her lights. This twisting is often accompanied by a swinging of her abdomen from side to side like a metronome, which, to complete the exhibition, gives the effect from a distance of the light brightening and dimming.

The display usually lasts for a couple of hours, after which, if she hasn’t been successful in attracting a mate, she turns off the light and retreats back into the grassy tussocks to prepare for a repeat performance the following night. The females are remarkably sedentary and are often seen displaying from the exactly the same spot until they either snag a mate or die an exhausted spinster after around ten consecutive nights of lighting up the night.

The numbers of glowing females can vary enormously from just a few females at small sites, to Brush Hill in Buckinghamshire, the location thought to contain the largest colony of glow-worms in Britain, with 320 females counted in one visit in 2007.

The male glow-worm looks very different to the female, because he has to be mobile in order to track down the displaying females, and so has a fully functioning pair of wings tucked away under his wing cases. He normally takes flight shortly after the females have started glowing and flies a couple of metres above the ground until he spots a virgin female. He will then drop out of the sky with unerring accuracy next to the female and attempt to climb on her back. It is not uncommon to have a number of suitors chasing a single female, meaning a form of rugby scrum can sometimes ensue as they jostle for position.

Like the adult female, the male cannot eat and so has a very limited adulthood. Once mating is over, the exhausted male dies, usually no longer than a week after emerging from his pupa for his date with destiny. His death is closely followed by the female’s after she has dutifully discharged her eggs to produce the next generation.

Although found all over Britain, glow-worm colonies are most abundant in southern England. They can be seen in grassland of every type, apart from sites that have been ‘improved’ with fertiliser or heavily sprayed with insecticides, and also occur in moorland, heathland and occasionally woodland. The spectacle is mostly a rural phenomenon, and country anecdotes abound of glow-worms being put in jam jars to read by at night!

The last 50 years are thought to have seen a steady fall in the number of colonies thanks to the usual lethal cocktail of habitat destruction, fragmentation and pollution. Artificial lights may well also present a problem as the males could be distracted by the lights and find it difficult to spot the females in the glare. Let’s hope, however, that these magnificent insects continue to bring light into our lives for many years to come.

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