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Mozambique Diary: Webspinners

An adult female of a yet unidentified webspinner from Gorongosa National Park.

An adult female of a yet unidentified webspinner from Gorongosa National Park.

It has been a busy couple of months for me – first organizing a month-long biodiversity survey in Gorongosa National Park, then dealing with various aspects of our newly created E.O. Wilson Biodiversity Laboratory. But now that I am home I can process all the photos taken in Mozambique and, finally, write a few long overdue blog posts.

Our second biodiversity survey of the park started with a week of sampling in the Sand Forest, an interesting plant community near Chitengo, the park’s main camp. While somewhat underwhelming at first glance, this stunted forest that grows on remarkably infertile, pale and sandy soils, produced some of the finest discoveries of the survey. It was also an exciting place to be, on the account of roaming elephants (who really didn’t like people invading their private feeding ground) and a radio-collared male lion (who, I was told by our lion researcher Paola Bouley, might actually “like” people).

Males of many webspinner, such as this cosmotropical Oligotoma saundersii, are fully winged. Their wings can easily flex in half over the top of the body to help them move backward in the narrow silky corridors.

Males of many webspinner, such as this cosmotropical Oligotoma saundersii, are fully winged. Their wings can easily flex in half over the top of the body to help them move backward in the narrow silky corridors.

The first thing that I noticed was that many tree trunks in the forest were covered with extensive carpets of silk. This was great because for the last two years I had been searching in Gorongosa for the elusive webspinners (Embiidina), an order of semi-social insects that build intricate silk corridors on trees and rocks. No species of webspinners has ever been recorded from Mozambique but I knew that they had to be there. To be precise, I did find a webspinner once in Gorongosa, but it was an introduced, Asian species Oligotoma saundersii, which has a nearly cosmotropical distribution. But the animals on the trees of the sand forest were clearly something very different.  For one, they were huge. I am used to webspinners being tiny, brownish insects that you look for with a magnifying glass. But one adult female that we collected was pitch black and nearly 25 mm long, which probably makes her the largest webspinner in the world (the largest webspinner that I could find a record of is the South American Clothoda, which grows to 20 mm.) But despite their size these insects were not easy to find. I ripped through dozens of their silky colonies but found only a handful of specimens. Only later did I realize that during the day these insects were hiding deep in the crevices at the base of the tree or in debris-filled nooks between branches.

The thin sheet of silk acts as an invisibility cloak, protecting foraging webspiners from their principal enemies, ants.

The thin sheet of silk acts as an invisibility cloak, protecting foraging webspiners from their principal enemies, ants.

Webspinners have fascinated me for a long time. They are one of those animal groups that don’t attract much attention because of their small size and unassuming physique but, once you learn about their biology, they become very hard to ignore. The webspinners’ most obvious claim to fame is their ability to spin silk. But how do they do it? Spiders spin silk from spinnerets located at the tip of their abdomen (opisthosoma), but all insects (caterpillars, ant larvae, gryllacridid crickets, to name a few) have them located on their mouthparts. Or so the entomologists thought. And so strong was this conviction that early morphological descriptions of webspinners included silk-producing tubercles on the labrum which, upon closer inspection, turned out to be purely imaginary – as it happens, webspinners possess unique silk-producing, glands on their front tarsi, and not on their mouths. This explains their characteristic behavior of constantly waving the front legs – they are spinning silk, but the individual strands as so microscopically thin as to be completely invisible to the human eye. Only once hundreds or thousands of individual strands have been spun together do they begin to appear as a thin sheet of soft silk. The proteins that make up the spider and moth silk are some of the strongest organic compounds, resistant to breaking and very flexible. In contrast, the webspinners’ silk is remarkably weak and tears quite easily. This may have to do with its primary function – rather than being used to capture prey or protect a fragile developing pupa, it is merely a cloaking device that makes the insects invisible to ants while the webspinners graze lichens that cover bark or rocks. I have watched ants walk right on top of webspinners separated only by a diaphanous sheet of silk, while the webspinners were happily grazing on lichens, completely unperturbed by the presence of their deadly enemies.

The second function of the silk is the protection of eggs, which the female covers with silk and guards them until they hatch. She stays with the eggs mostly to chase away parasitoid scelionid and plokiophilid wasps, and her presence increases the survival of eggs by 50%. But once the eggs are about to hatch the mother must remove the silk, otherwise the nymphs will not be able to emerge. She then stays with her children until they are ready to fend for themselves, initially masticating their food and spinning the silk corridors. She then leaves to start another colony.

The front tarsi of webspinners are strongly enlarged to accommodate silk-producing glands.

The front tarsi of webspinners are strongly enlarged to accommodate silk-producing glands.

Interestingly, some webspinners are the only social insects that are inquilines within the societies of other social animals – two species of Oligotoma from India build their societies inside colonies of a social spider Stegodyphus sarasinorum (but continue to spin their own silk). Another, Oligotoma termitophila, lives in termite colonies in Sudan.

So, what’s next for my Mozambican webspinners? Next time I am in Gorongosa I plan to look into their biology, and figure out what their colony structure and dispersal patterns are. The species also needs to be identified and described, which I should be able to do once I bring the specimens back from Mozambique (we hit a little snag with the export permits). I also plan to look for other species on Mt. Gorongosa. Who knows, I may also be able to find the webspinners’ closest relatives, the amazing zorapterans.

Silken galleries of webspinners covering trees in the Sand Forest of Gorongosa.

Silken galleries of webspinners covering trees in the Sand Forest of Gorongosa.

My life is now complete

A wingless form of zorapteran (Zorotypus hubbardi) from Sapelo Island, GA

A wingless form of zorapteran (Zorotypus hubbardi) from Sapelo Island, GA

When I set off for a long weekend on Sapelo Island in Georgia to teach insect photography at the BugShot workshop, it never occurred to me that the trip would culminate in completing a life-long quest. I am not one to keep bucket lists of things to see or do but, as an entomologist, I always hoped to personally collect all extant orders of insects. The most conservative classifications list about 28 orders of these animals, while others divide the class into more ordinal taxa (for example, Vitaly M. Dirsh divided the Orthoptera into 14 separate orders; thankfully nobody paid any attention to such craziness.) Regardless of the semantics, over the years I have collected all major lineages of insects, including such rarities as the Mantophasmatodea (in fact, I collected the second live specimen ever found; the first one was collected by Namibian entomologist John Irish about 10 minutes earlier), Grylloblattodea, or Strepsiptera. But one group has consistently eluded my grabby hands – the Zoraptera.

Warm, humid, and festooned with Spanish moss, the oak forest of Sapelo Island, GA, is an ideal habitat for the Zoraptera.

Warm, humid, and festooned with Spanish moss, the oak forest of Sapelo Island, GA, is an ideal habitat for the Zoraptera.

Described in 1913 by Italian entomologist Filippo Silvestri, Zoraptera are the least diverse order of insects – only 39 species are known, all in the genus Zorotypus (Mantophasmatodea have fewer species, but are divided into multiple genera and families.) As far as rare insects go, Zoraptera may appear somewhat underwhelming in their size and morphology – most species are only about 3 mm long, usually pale yellow or brown, blind and wingless. Their preferred habitat is also not very sexy as Zoraptera are found mostly in rotten logs across tropical and subtropical parts of the world, feeding on fungal hyphae or springtails. They are rather picky in their selection of habitat, and will only survive in logs that have reached the “Zorapteran stage” of decomposition – nothing more, nothing less (the five-stage classification of log decay was introduced in 1959 by E.O. Wilson, who to this day considers himself a zorapteran aficionado). Looking for Zoraptera is akin to looking for a grain of salt in a sugar bowl – in a log teaming with ants, termites and springtails you need to be able to spot a nearly microscopic, whitish insect that runs frantically in all directions, whose body proportions are only slightly different from those of a newly hatched termite nymph. It took me several hours of ripping through decaying logs and enduring countless stings of trap-jawed ants (Odontomachus) before I noticed an eensy dot of an insect that looked a little different. Even as I was putting it in a vial I was not quite sure that it was really a zorapteran, but my suspicion was confirmed the moment I looked at it through the macro lens of my camera.

Most zorapterans are pale, wingless and blind. Winged forms only appear if the decaying long in which they live can no longer support the population of these insects.

Most zorapterans are pale, wingless and blind. Winged forms only appear if the decaying log in which they live can no longer support the population of these insects.

But of course one should not judge the Zoraptera by their unassuming demeanor, for their behavior and reproductive biology are some of the most interesting among all insects. First, despite their name (zor [Gr.]=pure, aptera=wingless), winged forms are found in all species, albeit they only appear when the time comes to leave the log when it shifts from the “Zorapteran” to “Passalid stage” of putrefaction. And, once a new, nicely rotten habitat is found, the wings fall off. This type of behavior is not unique to the Zoraptera (aphids display a similar wing polymorphism), but what happens next is.

Zoraptera are not truly social, but often live in groups of 30+ individuals of various ages. But, unlike termites and ants, all individuals in the colony can reproduce, at least in theory. The colony is strictly patriarchal – the dominant individual is always the oldest male who maintains a harem of females and fights off younger males. Only when the senility kicks in, younger males have a chance to take over the top spot. This type of a male-dominated society is unique among arthropods, where it is always the females who control both reproduction and individual status in the colony.

Even more interesting is the way males inseminate the females. All across the animal kingdom males tend to be rather generous with the dispensation of their reproductive cells (to put it mildly), while females are frugal with their eggs, and choosy when it comes to mating. But in Zoraptera things are different – to inseminate the female the male produces only one (one!) sperm cell. And not just any sperm – the zorapteran spermatozoa are about 3 mm long, which, if you recall, is the average body length of the entire animal. Not surprisingly, males of these insects are not particularly eager to mate and it is the female who does most of the courting. Why this happens is not entirely clear, but most likely the single, giant sperm cell fills the female spermatheca (a sperm storage space that allows the female to inseminate eggs long after the copulation) and precludes her from mating with other males.

I wish I could have spent more time in Georgia – it would have been nice to see armadillos in a form other than flattened pancakes on the highway. On my drive from Savannah to Atlanta I counted 27 carcasses of these animals killed by cars.

I wish I could have spent more time in Georgia – it would have been nice to see armadillos in a form other than flattened pancakes on the highway. On my drive from Savannah to Atlanta I counted 27 carcasses of these animals killed by cars.

As I drove back from Savannah to Atlanta, counting armadillo roadkill (27), I couldn’t help but wonder what the bar scene of our species would look like if men produced only one, 6 feet long reproductive cell during each mating. In the end, I am happy for the zorapteran males, but will keep my millions, thank you very much.

Zorapteran (Zorotypus hubbardi), the only species of the order Zoraptera found in the United States.

Zorapteran (Zorotypus hubbardi), the only species of the order Zoraptera found in the United States.

BugShot 2014: Sapelo Island, GA

Polyrhachis

Intimate portraits: A queen ant (Polyrhachis armata)

My arrival in Johannesburg has brought a welcome respite from the unbearable winter of New England, and tomorrow I fly to Gorongosa National Park to begin preparations for the official opening of the E.O. Wilson Biodiversity Laboratory on March 27th. Stay tuned for updates and photos!

But there is something else that I am very excited about. Last year I was invited by Alex Wild to teach an insect photography workshop in Belize, the famous BugShot, and this year we are doing it again. This time the workshop will take place on Sapelo Island in Georgia, a place I have never been to but always wanted to visit. Insect life is bound to be spectacular – among other things I expect to find there Brunneria borealis, North America’s largest praying mantis and the world’s only fully parthenogenetic species of these insects. There are webspinners (Embioptera) there, two species of sylvan katydids (Pseudophyllinae), and over 100 species of other orthopterans. This is going to be good.

High-speed macrophotography: Periodical cicada (Magicicada septendecim)

High-speed macrophotography: Periodical cicada (Magicicada septendecim)

The workshop will take place on May 22-25 and there are still a few empty slots left. If you want to learn macrophotography, perfect your technique or learn a new one, or simply find out amazing facts about invertebrates, then you should join entomologists and photography experts Alex Wild, John Abbott, and myself on this fun adventure. Visit the BugShot website to find more details.

Wide-angle macro: Sylvan katydid (Celidophylla albiomacula)

Wide-angle macro: Sylvan katydid (Celidophylla albiomacula)

Time lapse macrophotography: A molting katydid (Enyaliopsis petersi)

Time lapse macrophotography: A molting katydid (Enyaliopsis petersi)

Ambient light macrophotography: Atlantic shield-back (Atlanticus testaceus)

Ambient light macrophotography: Atlantic shield-back (Atlanticus testaceus)

Mozambique Diary: A welcoming conehead

A female conehead (Ruspolia consobrina) found in a Maputo hotel.

A conehead katydid (Ruspolia consobrina) found in a Maputo hotel.

Last night I arrived in Mozambique’s capital Maputo. It was almost midnight when I finally got to my hotel, tired to the point of barely being able to keep my eyes open after more than 20 hours on the plane. But the scent of tropical, humid air was too much for me to resist, and so I put on my headlamp and took a quick stroll around the hotel’s grounds. 

It is the wet season now, and although it did not rain last night the atmosphere felt very humid. But it quickly became apparent that the hotel’s garden had been sprayed with pesticides, as evidenced by almost no insect activity on its beautifully manicured lawns. Across the street from the hotel insects were flying around street lamps and several species of crickets and katydids could be heard in a distance; I even heard the unmistakable call of a pamphagid grasshopper. “Oh, well”, I thought, and at that moment a large katydid flew in from across the fence and landed on the wall in front of me. It was a female conehead katydid (Ruspolia consobrina), a species I knew well from Gorongosa. After a few minutes I found a second individual, trapped in the foyer of the hotel.

Coneheads of the genus Ruspolia are handsome insects, with bodies resembling blades of grass, which makes sense as these are the plants they mostly feed on. Their mandibles are massive and strangely asymmetrical, a feature they share with several other grass-feeding katydid genera. Why is one mandible, usually the left one, much larger than the other is unclear, but it likely helps with stabilizing and cracking seeds of grass that these insects like to eat. And because they feed on such nutritious food, bodies of Ruspolia can get very fat. Combine it with the fact that coneheads can occur in large, almost plague-like numbers in certain parts of Africa, and it is not surprising that they feature prominently in the diet of many African peoples. They high fat content also allows coneheads to survive long periods of low food availability, or even starvation (a topic I covered in an earlier post).

I quickly snapped a few pictures of the katydid, happy to see it minutes after my arrival, and collapsed on the bed on the verge of total exhaustion. Of course I woke up a couple of hours later, unable to fall back asleep because of the time change and so, here I am, writing this blog well before sunrise – a first for me.

Ruspolias

Coneheads (R. consobrina) are highly polymorphic – these three individuals are from the same population in Gorongosa National Park.

Music in my head

Male Carolina ground crickets (Eunemobius carolinus) are the hardiest of all my garden's musicians, and may continue to woo females with their song well into late November.

Male Carolina ground crickets (Eunemobius carolinus) are the hardiest of all my garden’s musicians, and may continue to woo females with their song well into late November.

I have always wanted to be a musician. Not that I have any particular musical talents (and never learned to read music), but my fascination with sound was definitely one of the reasons for becoming an expert in the taxonomy of orthopteroid insects, nature’s preeminent musicians. Few things are more pleasant to me than sitting on the deck of our house near Boston on a warm summer evening – a high frequency sound recorder in one hand, a glass of gin & tonic in the other – and getting lost in the hypnotic chorus of about a dozen species of katydids and crickets that share our garden with us. (The best part of this activity is that I can call it “data collecting”.) Now that the summer is sadly over, all I have is the memory of beautiful garden soundscapes, and a bunch of recordings. There are still some strugglers out there – just the other night I found a Sword-bearing conehead (Neoconcephalus ensiger) singing on the lawn in front of our house – but let’s face it, it will be very quiet very soon. And thus I thought that this might be a good time to put all of this year’s recordings together into one composite soundscape, and relive the aural painting that I am privileged to experience every summer.

Some of the cricket species I recorded in or near my garden. The number under each name represents the sequence of joining the musical performance in the composite recording below.

Some of the cricket species I recorded in or near my garden. The number under each name represents the sequence of joining the musical performance in the composite recording below.

Some species, such as the ubiquitous Carolina ground cricket (Eunemobius carolinus), produce calls that are not especially musical, but rather reminiscent of a buzz made by overtaxed power lines. Others, like the Treetop bush katydid (Scudderia fasciata), make irregular, high frequency clicks that show no discernible rhythm. But, as I listen to the evening’s ambience, a repeating pattern begins to emerge. Snowy tree crickets (Oecanthus fultoni) stridulate in a way that is both highly rhythmical and melodious (Joni Mitchell fans will recognize this species in the song “Night Ride Home”), while the frequency-modulated chirps of Field crickets (Gryllus veletis) add a nice, if somewhat irregular, punctuation.

Some of katydid neighbors. Just like with the crickets, the number under each name represents the sequence of joining the musical performance in the composite recording below.

Some of katydid neighbors. Just like with the crickets, the number under each name represents the sequence of joining the musical performance in the composite recording below.

As the night falls more and more species join in. A Two-spotted tree cricket (Neoxabea bipunctata) utters short, piercing cries, usually in sonic pairs, sometimes in series of threes or fours. And although I cannot hear it, I know that the Drumming katydid (Meconema thalassinum), a relatively recent arrival to North America from Europe, is banging one of his hind legs against the bark of the large oak in our garden, creating a percussive line for the rest of the ensemble. Why this species has lost its ability to stridulate and instead evolved a drumming behavior is a mystery, but it is likely that the shift was driven by either a predator or a parasite the had used its (originally) airborne calls to find the singing males and do unspeakable things to them.

And finally, later at night (and later in the season), the True katydid (Pterophylla camellifolia) adds its voice to the chorus. This spectacular insect, whose song is recognizable to anybody who’s ever lived on the East Coast of the US, is the northernmost member of a largely tropical lineage of katydids, the Pseudophyllinae. Despite them being very large and remarkably common insects (you can hear true katydids in the middle of Boston and other large cities), few people ever get the chance to see one – they spend their entire lives high in the canopies of the tallest trees, and are encountered only occasionally, for example when a gust of strong wind knocks them down onto the ground. I have lived surrounded by True katydids for the last 20 years, but can count all my encounters with them on the fingers of one hand. Incidentally, if you ever wondered where the word “katydid” came from, listen to this species’ call. The more northern populations (and thus the ones that the Pilgrims first heard, and apparently were afraid of) have a call consisting of 2-4 syllables that can be interpreted as the sound “ka-ty-did” (or, as the legend goes, “katy-she-did-it”, thus betraying the identity of some murderous lady).

My foot has been tapping since the tree crickets started calling, and now, with the strong beat of the True katydid, I can’t help but imagine melodic lines filling the spaces in between the pulses. I sip my drink and let the mind wander.

A sonogram of a composite recording of most of the orthopteran species singing in my garden. On a good night I can hear them all, but here I decided to add them one by one to the recording to make each species' song stand out. Click here to listen to this soundscape. Please note that some species (esp. Scudderia and Microcentrum) may not be audible to a certain group of listeners (I am talking about you, men 35 or older; I count myself incredibly lucky for still being able to hear all my local species – but who knows for how long). It will help if you listen to this recording through headphones or external speakers; most built-in computer speakers may not be able to reproduce all frequencies (esp. the low frequency drumming of Meconema). (If you would like to see an animated sonogram with species names appearing as they join the chorus, click here; it is a large file, suitable only for a fast connection.)

A sonogram of a composite recording of most of the orthopteran species singing in my garden. On a good night I can hear them all, but here I decided to add them one by one to the recording to make each species’ song stand out. Click here to listen to this soundscape. Please note that some species (esp. Scudderia and Microcentrum) may not be audible to a certain group of listeners (I am talking about you, men 35 or older; I count myself incredibly lucky for still being able to hear all my local species – but who knows for how long). It will help if you listen to this recording through headphones or external speakers; most built-in computer speakers may not be able to reproduce all frequencies (esp. the low frequency drumming of Meconema). (If you would like to see an animated sonogram with species names appearing as they join the chorus, click here; it is a large file, suitable only for fast internet connections.)

BugShot 2013 in Belize

There are still a few slots available for BugShot 2013, a great opportunity to learn macrophotography in the rainforest of Belize from Alex Wild, Thomas Shahan, John Abbott, and yours truly. It is going to be a great event, at a fantastic location. You will not only discover the carefully guarded secrets of some of the best insect photographers in the world (e.g., what cameras they really use, how they drug their insects so that they sit absolutely still* etc.), but you will also learn a lot about insect biology and behavior, and visit a variety of Neotropical habitats.

Head on the BugShot.net to grab one of the few remaining spaces.

*) I am kidding, of course – real nature photographers never drug, chill, or kill their subjects.

The Greatest Show on Earth, happening now

The best time to see Atlantic horseshoe crabs (Limulus polyphemus) is on the nights of the full and new moon in May and June.

The best time to see Atlantic horseshoe crabs (Limulus polyphemus) is on the nights of the full and new moon in May and June.

I am still in Mozambique, and will be here for a few more weeks, but I simply must take a quick break from describing African nature to highlight a spectacular phenomenon that is taking place right now along the eastern coast of North America – the mass spawning of the Atlantic horseshoe crabs (Limulus polyphemus). Watching these magnificent animals is to me one of the most beautiful natural events that one can witness, and I encourage everybody living on the East Coast to take a trip to the beach this and next month (this year the best time to see them are nights of May 24th, and June 9th and 23rd.) What follows is a short excerpt from my book “Relics” (Chicago University Press 2011), describing my experience of watching horseshoe crabs on the beaches of the Delaware Bay.

“As hundreds of biting flies did their best to drain us of every drop of blood, my friend and fellow photographer Joe Warfel and I stood on the beach, waiting for the spectacle to begin. The sun grew dim, and the high tide was nearing its peak. There were a few people on the beach when we first arrived, but by now they had all disappeared, and we were the only witnesses to what was about to unfold. I started to tell Joe how strange it was that nobody else stayed to watch, but swallowed a fly and decided to quietly enjoy the rest of the evening. First came the big females. Nearly all had males in tow. In the dimming light we could see spiky tails of hundreds more as they tumbled in the waves, trying to get to the dry land. By the time the sun fully set, the beach was covered with hundreds of glistening, enormous animals. Females dug in the sand, making holes to deposit their eggs, nearly 4,000 in a single nest, while the males fought for the privilege of fathering the embryos. Fertilization in horseshoe crabs is external, and often multiple males share the fatherhood of a single clutch. Equipped with a pair of big, compound eyes (plus eight smaller ones), capable of seeing the ultraviolet range of the light spectrum, male horseshoe crabs are very good at locating females even in the melee of waves, sand, and hundreds of other males.

Delaware Bay is the best place in the world to see these magnificent animals. On a good night one could easily see 100,000 horseshoe crabs.

Delaware Bay is the best place in the world to see these magnificent animals. On a good night one could easily see 100,000 horseshoe crabs.

Horseshoe crabs have been around longer than most groups of organisms that surround us now. A recent discovery in the fossil deposits of Manitoba, an interesting little creature named Lunataspis aurora, proves that horseshoe crabs quite similar to modern forms were already present in the Ordovician, 445 million years ago. By the time the first dinosaurs started terrorizing the land in the Triassic (about 245 million years ago), horseshoe crabs were already relics of a long-gone era. And yet they persisted. Dinosaurs came and went, the Earth changed its polarity and climate many times over, but horseshoe crabs slowly plowed forward. Yet during this time they changed surprisingly little. Species from the Jurassic were so similar to modern forms that I doubt I would notice anything unusual if one crawled in front of me on the beach in Delaware. Somehow horseshoe crabs had stumbled upon a lifestyle and morphology so successful that they were able to weather changes to our planet that wiped out thousands of seemingly more imposing lineages (dinosaurs and trilobites immediately come to mind.) But despite claims to the contrary by creationists and other lunatics, they kept evolving. Modern horseshoe crabs, limited to three species in Southeast Asia and one in eastern North America, differ in many details from their fossil relatives. We know, for example, that many, if not most of fossil horseshoe crabs lived in freshwater, often in shallow swamps overgrown with dense vegetation, and some might have even been almost entirely terrestrial. Currently only the mangrove horseshoe crab Carcinoscorpius rotundicauda from the Malayan Peninsula routinely enters rivers, and is the only species to lay eggs in fresh or brackish water.

Even Sir David Attenborough, the man who probably witnessed more natural spectacles than any other human being, is fascinated by the spawning of horseshoe crabs. Here he demonstrates the improper way of holding a horseshoe crab (never hold them by their telson) while on the beach in Delaware during the filming of the BBC series "Life in the Undergrowth".

Even Sir David Attenborough, a man who probably witnessed more natural spectacles than any other human being, is fascinated by the spawning of horseshoe crabs. Here he demonstrates the improper way of holding a horseshoe crab (never hold them by their telson) while on the beach in Delaware during the filming of the BBC series “Life in the Undergrowth”.

The following morning Joe and I found the beach covered with horseshoe crab eggs. Well-rested and ready to start a bright new day the flesh-piercing flies attacked us with a renewed enthusiasm. Flailing our arms and swatting dozens at a time we went about flipping crabs stuck on their backs in the sand, and started to look for particularly big clutches of eggs. Although females burry the eggs in the sand, the returning tide washes out many of them. Freshly laid eggs are small, not larger then half a grain of rice. Surprisingly, the eggs grow as they develop, eventually becoming more than twice as large. This, of course, is impossible. The “growth” is an illusion, the result of the production of an external, thin membrane by the developing embryo. A fully developed egg, which at this stage has spent two weeks in the sand, resembles a tiny glass aquarium, with a petite horseshoe crab twirling inside, impatient to break the walls of its miniature prison. Once free, the larva (or at least the lucky ones) catches a wave back into the ocean and will spend about a week floating freely, before settling on the bottom of the shallow shore waters to begin life akin to that of its parents.[…]“

Tiny horseshoe crab larvae, known as the trilobite larvae, twirling in their aquarium-like egg shells. Soon they will break free to begin a short pelagic period, after which they settle on the bottom of the ocean to begin a lifestyle similar to that of their parents.

Tiny horseshoe crab larvae, known as the trilobite larvae, twirling in their aquarium-like egg shells. Soon they will break free to begin a short pelagic period, after which they settle on the bottom of the ocean to begin a lifestyle similar to that of their parents.

Just like their distant relatives, scorpions, horseshoe crabs display green fluorescence under the ultraviolet light.

Just like their distant relatives, scorpions, horseshoe crabs display green fluorescence under the ultraviolet light.

Limulus5

Atlantic horseshoe crabs on the Prime Hook Beach near Milford, Delaware.