This morning, in my bathroom, I was faced with a dilemma.
A guest post by Jen Guyton
In my lap was a specter, one of the most elusive animals in sub-Saharan Africa. I’d been waiting years to see it, and now it was weighing abrasively on my thighs like a sack of bricks stuffed into a giant pinecone. It wiggled and unfurled its roly-poly body just enough to reveal an eye like sticky caviar, its tongue whizzing in and out and reinforcing the illusion that this scaly orb was a dragon come to life.
But it was a warm-blooded, placental mammal, confirmed by the tiny body double that was furled in her grasp, suckling at the teats exposed on her underbelly. The mother and her pup were ground pangolins (Smutsia temminckii), one of eight species belonging to the mammalian order Pholidota, found only in Africa and southeast Asia. Though often called scaly anteaters, pangolins are unrelated to the Vermilingua, the suborder containing true anteaters. Actually, pangolins aren’t closely related to much of anything; these animals are unique, clinging to a long, isolated branch on the tree of life.
We were in Gorongosa National Park, Mozambique, and someone had told us about her. There was a man in a village across the river, the whispers went, selling her for the low price of 22,000 meticais (about $700 USD). Like rhinos, pangolins have fallen victim to a deeply-held misconception that their keratinous scales hold medicinal magic: that they can cure skin disease, reduce swelling, or even conquer cancer. I’ll tell you now: save yourself the money and the risk of jail time, and just chew on your nails – they are chemically and physiologically the same.
One day and a sting operation later, the pangolin was in my lap. Park rangers, working with the local police, arrested the poachers and rescued the animals. We were driving them out into the core of the park, where we’d release them, safely distant from grasping human hands. Though the pinecone plates of a pangolin’s back can and do stand up to being chewed on by lions, these animals are no match for a human that’s interested enough to simply pick one up and carry it off. Their only other defense is their smell, an indescribable odor that originates from a noxious acid secreted from glands below the tail.
I ran my hands along the pangolin’s scales. They were grooved and brittle-chipped, crooked and mud-splattered like fingernails that had seen many years of working with the land. In Asia, the scales of confiscated pangolins bear the circular scars of punches used for medicine. Even the artful hand of evolution, which had crafted this unique armor from a plush pelt, couldn’t save them.
As she unrolled herself from her fortress, a second head surfaced, tiny and pale. It was her male pup, the only one that will be born until he reaches sexual maturity in two years. He was born in captivity, a side effect of stress, and an unrealized bonus prize for the poacher. His scales were half-baked, pliable, and the dark shriveled stump of an umbilical cord poked from his round belly. He moved in the shivering stutters of an infant still unsure about the world.
As the pup crawled up my arm, the mother thrust out a hooked hand to right herself. Her claws, the length of my fingers, gripped my jacket like rusty nails and tore a gaping hole in the material as they bore into my side. I jumped, and she rolled back into a ball, her pup safely inside. These formidable sickle-claws are used to tear open termite mounds and ant nests, shredding the hard earth in search of scrambling adults and doughy larvae. The pangolin laps them up with its sticky-salivating tongue, longer than its own body and the longest relative to body size of all known mammals. Because pangolins lack teeth entirely, keratinous folds line their stomachs with inverse armor, grinding the insects to bits with the help of ingested pebbles.
We finally reached an appropriate site: far from the park’s perilous edges, the forest bulged above a tapestry of termite mounds. We set her gently on the ground, and waited.
Pup clinging to her back, she stood and sniffed the air, taking a few moments to orient herself to her new and safer home before choosing a bearing. Her scales clack-clacking, she ambled away on her hind feet like a drunken Velociraptor, tail out and claws curled against her chest. It’s hard to walk on all fours when you’ve got scythes for hands.
In Chinese mythology, pangolins are wayfarers. It’s said that they travel the world by digging through the core of it, tying the earth together with a vast underground labyrinth. In Cantonese, they’re called chun-shua-cap, “the animal that bores through the mountain.” I’d like to think she’s safely reached the Alps by now.
Text and artwork ©Jen Guyton 2014
If you would like to learn more about pangolins, and threats they face from the illegal wildlife trade, read a recent expository piece on the CNN website.
“Hey, where is the spider post?”, you may be asking if you arrived at this page by following one of the thousands of links that sprung up overnight in the online media and social circuits. In the fine tradition of online publishing I took the liberty of pulling a “bait-and-click” switcheroo, and turning the hysteria surrounding the Goliath birdeater’s story into a teaching opportunity. And thus, please bear with me, and read this post to the end (where you will find the original post about the spider) before banging out an angry comment in ALL CAPS.
For some reason, probably related to the proximity of Halloween, my blog post about the Goliath birdeater spider received an inordinate amount of attention, and has been republished, reinterpreted, outright stolen, and vilified all over the Internet. This one post on my obscure blog is now receiving in excess of 120,000 unique visits every day, and comments are pouring in. Alas, most of them are somewhat less than positive, and I am beginning to wonder if I really am a “HORRIBLE person” who “will destroy the earth.” (I must admit that some of the trolls were touchingly tactful – they might have said ” F&*K you, a$$hole”, but they modified the foul words as not to offend my sensibility.) But why the vitriol?
You see, while talking to a reporter I explained that one of the specimens I describe in the blog had been collected and placed in a museum. This, combined with my comment of having seen this species only a handful of times, triggered a tsunami of self-righteous outrage at my murderous act which, according to the most vocal individuals, is bound to drive this species to extinction. In fact, I really fear for the Smithsonian Institution, this nation’s preeminent natural history collection. If a single spider collected by a scientist causes such an outrage then, surely, the 126 million specimens in its holdings will warrant burning it to the ground and crucifying all scientists working there.
But in all seriousness, why was the specimen collected? First, a bit of a background about the expedition to Guyana during which this took place. I was there with a group of biologists and Guyanese students at the invitation of the Ministry of Amerindian Affairs and the Environmental Protection Agency of Guyana. Our job was to conduct a comprehensive survey of animals and plants of the newly created Community Conservation Area, train Guyanese students in the methodology of biological surveys, and collect specimens for the Center for the Study of Biological Diversity at the University of Guyana. These specimens are used to both create permanent documentation of the species composition of a never before explored area of the country, and to train a new cadre of scientists and conservation professionals in identification and morphological diversity of organisms. And before you point out various alternative methods of documentation (photographs, sound recordings, non-destructive DNA samples), let me assure you that there is no substitute for the collection of physical specimens.
What about this particular spider? As I mention in the post below, Theraphosa blondi is indeed the largest spider in the world (although its legs are not foot long, as some media reported), and thus it makes a perfect specimen for teaching spider morphology. It is also a very common species, not protected or endangered, and collecting of a single individual poses absolutely no threat to its survival (a scientist picking up one spider is no different from a bird doing the same; if a stochastic event such as this can drive a species to extinction then this species is already doomed.) In fact, you can purchase Goliath birdeaters in many pet stores in the US or online for $20-100 a piece. But they are shy and elusive, and thus I was thrilled every time I saw one during a small handful of encounters with this species. Once the animal was properly euthanized and preserved, something that is never done lightly, it was carefully labelled and deposited in the collection in Guyana where to this day it serves as an important teaching tool. And, years from now, the same specimen may provide new data on spider anatomy, genetics, evolution etc. In addition to the spider, we also collected vouchers of 857 other species of animals and plants (excluding birds and large mammals), which are now deposited across various research institutions in Guyana, Venezuela, and the US.
Collecting and preservation of physical specimens is an integral, irreplaceable element of biological sciences. There is hardly a branch of biology that does not rely on the examination of organisms’ bodies (the only exception I can think of is ethology, and only some variants of it), be it for the purpose of their identification, understanding of the functions of their respiratory system, or the speed of transmission of neural signals. Museum collections, where specimens are preserved for future scientists, are a special, very important case. There specimens are often deposited not for a particular, clearly defined research project (such as when a geneticist examines thousands of fruit flies to measure the expression of a particular gene). Rather, collections serve as both a documentation of the current state of species composition in a particular time period or an area, or as a library of morphological and genetic diversity across a wide range of species. We cannot anticipate what questions will be asked, and answered, using specimens deposited in such collections. For example, the ban on the use of DDT, a horrible environmental pollutant, was based on the discovery made in ornithological collections that bird egg shells have been getting progressively thinner, thus leading to high mortality of birds, ever since the chemical began to be used. The spread of chytrid fungus that is wiping amphibian species across the globe was understood by examining specimens dating back a hundred years. Closer to my own research, the world’s only cave katydid is now listed as Endangered by the IUCN Red List and thus receiving a greater attention from conservationists, because I found 70-year old, unidentified specimens of this species, collected by a scientist who had no idea what a remarkable animal he was catching.
Can collecting specimens for scientific research threaten a species’s survival? The short answer is no, there is absolutely no evidence that any scientist has ever driven a species to extinction. Famous New Zealand 19th century ornithologist Walter Buller is sometimes accused of having collected birds to extinction, but a close examination of the numbers of specimens collected by him proves that his work had no impact on the birds’ populations; rather, his bird collection is now a sad repository of species exterminated in New Zealand by moronic, purposeful introduction of alien species and destructive agricultural practices on the islands.
And this is the key – species are never lost as a result of scientific collecting, but almost invariably because of the destruction of their habitat, or due to competition from alien species introduced by humans. And this loss of species is happening on an unimaginable scale – by some estimates 16,000 species quietly go extinct every year, some even before scientists have a chance to describe and name them. And this is why if I see something that may be new to science, even if I suspect that it might be rare and threatened, I will collect it and deposit it in a museum. Some years ago I found a new species of katydid in South Africa. I knew that its population was tiny and on the brink of disappearance. In fact, this species is now probably extinct. Not because I collected a few individuals, but because its only population was located in a tiny patch of a native yellowwood forest within a massive pine plantation, a patch that was already being cut down to be replaced by more non-native trees grown for timber. Had I not collected a few specimens of this animal, we would have never known it existed. Now, at least its tombstone has a name – Paracilacris periclitatus, The Endangered Katydid.
I could go on and on about why scientific collecting is needed, but I want to mention one last thing. Every single one of us is guilty of involuntary bioslaughter – we kill thousands of organisms without realizing that we do it. Look into the light fixtures of your house or the grill of your car, they are full of dead insects and spiders. That highway that you drive to work – each mile of it equals millions of animals and plants that were exterminated during its construction (and if you live in an area of particularly high endemism, California or New Zealand for example, its construction probably contributed to pushing some species closer to extinction). That tofu that you eat because meat is murder – it probably comes from Brazil, where massive soy plantations stretching from one horizon to another have replaced its once thriving rainforest and led to the disappearance of thousands of species.
It is very easy to fixate on an individual case of an organism being deliberately euthanized. We do it because it is convenient emotionally – it is much easier to feel superior when we can point a finger at somebody who does it consciously, even if for a good, justifiable reason, but we don’t like to think about those trillions of animals and plants that we kill by virtue of simply going to a grocery store.
And now, enjoy the story of the Goliath birdeater.
The sound of little hooves in the night
When I go out at night into the rainforest to search for katydids I don’t like to have any company. Not that I am particularly antisocial, but tracking skittish and cryptic animals is an activity that’s better done alone. I walk slowly, trying not to disturb anything and anybody, slowly scanning the vegetation and the forest floor in the light of my headlamp. Every now and then I turn the light off to fully immerse myself in the ambient sounds of the forest, which often helps me pinpoint a faint trill made by a katydid’s wings. A few years ago I was deep in the rainforest of Guyana doing just that – listening to the sounds of the night in a complete darkness – when I heard the rustle of an animal running. I could clearly hear its hard feet hitting the ground and dry leaves crumbling under its weight. I pressed the switch and pointed the light at the source of the sound, expecting to see a small mammal, a possum, a rat maybe. And at first this is what I thought I saw – a big, hairy animal, the size of a rodent. But something wasn’t right, and for a split second the atavistic part of my brain sent a ping of regret that I didn’t bring any companion with me on this particular night walk. But before that second was over I was lunging at the animal, ecstatic about finally seeing one of these wonderful, almost mythical creatures in person.
The South American Goliath birdeater (Theraphosa blondi) is the largest spider in the world. For all the arachnophobes out there this is probably a good excuse to pave over large swaths of the Amazonian rainforest, but for the rest of us this species is one of biodiversity’s crown jewels. Although far from being the largest member of the subphylum Chelicerata – this honor belongs to horseshoe crabs – Goliath birdeaters are ridiculously huge for a land arthropod. Their leg span approaches 30 cm (nearly a foot) and they weigh up to 170 g – about as much as a young puppy. They truly are Goliaths, but are they bird eaters? Alas, the truth is a bit less exciting. Although definitely capable of killing small birds, they rarely have a chance to do so while scouring the forest floor at night (however, there is some anecdotal evidence that they may feed on bird eggs if they run across a nest). Rather, they seem to be feeding on what is available in this moist and warm habitat, and what is available is earthworms – lots of them.
But how do they get to be so big? Apparently, according to one study (Makarieva et al., Proc. R. Soc. B  272), it has to do with their metabolic rate, which is lower than in the Goliath birdeater’s relatives. This allows it to function with lower levels of oxygen reaching its tissues and organs than those required by smaller, more active spiders. In other words, the bigger the body the more difficult it is to provide oxygen to all its parts if the metabolic rate is to remain constant. Regardless of the reason, because of its gargantuan size, the Goliath birdeater is probably the only spider in the world that makes noise as it walks. Its feet have hardened tips and claws that produce a very distinct, clicking sound, not unlike that of a horse’s hooves hitting the ground (albeit, admittedly, not as loud). But this is not the only sound this spider makes.
Every time I got too close to the birdeater it would do three things. First, the spider would start rubbing its hind legs against the hairy abdomen. “Oh, how cute!”, I thought when I first saw this adorable behavior, until a cloud of urticating hair hit my eyeballs, and made me itch and cry for several days. If that wasn’t enough, the arachnid would rear its front legs and open its enormous fangs, capable of puncturing a mouse’s skull, and tried to jab me with the pointy implements. The venom of a birdeater is not deadly to humans but, in combination with massive puncture wounds the fangs were capable of inflicting, it was definitely something to be avoided. And then there was a loud hissing sound. For a long time the source of the sound was a mystery, but now we know that it is produced by “setal entanglement” – some of the hairs (setae) on the legs are covered with microscopic hooks that scrape against other, feather-like setae, producing the loud warning hiss.
A couple of years after my first encounter with Theraphosa blondi I was in South America again, walking alone at night in the rainforest of Suriname. Suddenly my foot brushed against something big and moving, and I nearly tripped. I froze, expecting a snake. “Nah, it’s just another Goliath birdeater. Aren’t you a cutie pie?”
Update: You can now purchase high quality prints of all images appearing in this post – just click on the image. For commercial use please contact Minden Pictures with inquires regarding licensing of these photos.
Yesterday evening, right before the weather turned nasty, as I stood on the deck over my garden I suddenly caught a sound wave, one that I immediately recognized but had never before heard around my house. I ran to grab my recorder and was able to capture a snippet of the call. Seeing me pointing my microphone towards his house, a neighbor approached me warily, inquiring if I am trying to find the property line. I explained what I was doing and he left, satisfied in his knowledge that I am just feeble minded, and not trying to sue him for his land.
The call was that of the Jumping Bush Cricket (Orocharis saltator), a species I first encountered a couple of years ago in Cambridge, MA. Since then I have been looking for other places where this pretty animal might live, but never expected to find it in my backyard. It is a species that belongs to the chiefly tropical subfamily Eneopterinae, and makes a fine addition to the chorus of crickets around my house, which now includes 12 species:
Jumping Bush Cricket (Orocharis saltator)
Handsome trig (Phyllopalpus pulchellus)
Say’s trig (Anaxipha exigua)
Carolina ground cricket (Eunemobius carolinus)
Allard’s ground cricket (Allonemobius allardi)
Striped ground cricket (Allonemobius fasciatus)
Two-spotted tree cricket (Neoxabea bipunctata)
Snowy tree cricket (Oecanthus fultoni)
Spring field cricket (Gryllus veletis)
Fall field cricket (Gryllus pennsylvanicus)
House cricket (Acheta domesticus) (introduced)
Eastern ant cricket (Myrmecophilus pergandei)
In 1911, after a short and apparently unsatisfying stint as a lawyer, Keppel H. Barnard left his native London and joined the staff of the South African Museum in Cape Town. First a mere lab assistant, he quickly ascended the ranks, in 10 short years reaching the position of the museum’s director, which he held until his retirement in 1956. Barnard’s life was dominated by two seemingly opposite passions. One was the study of aquatic animals, and during his productive career he laid the foundations of modern African ichthyology, carcinology, and malacology. But I probably would have never even heard of him if it wasn’t for his second obsession – mountaineering. In September 1925 his insatiable desire to scramble pointy rocks lead him to the ragged peaks and caves of Cederberg, a mountain range of red, Ordovician sandstone, about 150 km North of Cape Town. Once there, his zoological predilection kicked back in, and made him look into every nook and cranny to collect specimens for the museum. In narrow caves known affectionately as the Wolfberg Cracks he encountered large, spider-like insects, with spindly, striped legs and 6-inch antennae. But neither he nor anyone else knew what to make of them, other than that they might have been katydids.
For 70 years those specimens had sat in a dark corner of the museum until, after a string of my increasingly incessant letters, they were packed with a bunch of other unidentified material and shipped to me, then a young student of entomology working on a revision of southern African katydids. One glimpse at the specimens and I knew that they were special. Not surprisingly they were new to science — an always welcome but not unexpected occurrence. But the fact that the insects had been collected from caves was intriguing — no other katydid had ever been found in such a habitat. Could those be the first such animals? Their morphology certainly seemed to suggest it. Extremely long appendages and pale coloration are the hallmarks of troglophiles, organisms living in caves, and the new katydids fit this pattern.
To add to the mystery, all specimens were immature, and I could only speculate about what the adults might have looked like. I published a formal description of the new katydids, giving them the scientific name Cedarbergeniana imperfecta (immature katydid from Cederberg; now I wish I had named them after Barnard), but ever since I have been dying to find out more about their behavior and biology. Do they really live in caves? What do they eat? Can they sing? Are they solitary, like virtually all katydids, or do they live in groups, like cave crickets?
In the years that followed I have been able to visit Cederberg many times, and collected a lot of data about their biology. Yes, they truly are cave dwelling katydids, the world’s only, and yes, they are highly gregarious, often found in clusters of 20-30 individuals of various ages. The caves they prefer are cold, maintaining the chilly temperature of 12°C (54°F) throughout the year. Their habitat cannot be occupied by bats or hyraxes, which probably quickly do away with the tasty, surprisingly very slow-moving insects, thus limiting the number of available caves (interestingly, when exposed to higher temperatures they become phenomenal jumpers). I know now what sound they produce – a short, ultrasonic click. All their close relatives (katydids of the tribe Aprosphylini) produce long, continuous trills, but such a call would probably cause a lot of reverberation in a cave environment and thus make it difficult for a female to locate a singing male. I also know what they eat, a mystery that had bugged me after seeing the nearly sterile interior of the cave – they leave the cave at night to forage on grasses and other plants growing at the mouth of the cave. This behavior makes them, in technical parlance, trogloxenes.
Last month, during a short visit to Cederberg with my friend Jen Guyton, I approached Wolfberg Cracks with some trepidation. For one, it is a tricky climb and, having witnessed another friend tumble down the mountain and break several bones while looking for cave katydids, I did not want the same thing to happen to me or, especially, Jen – it would be hard to explain why young females who accompany me to the cave always end up falling off cliffs. But I was also worrying about the katydids themselves. Corey Bazelet, my collaborator at the University in Stellenbosch, and I have recently completed the IUCN Red List assessment of South African katydids, and the Cederberg cave katydid unquestionably ranks as Endangered. It is known only from a tiny handful of locations in the Cederberg Mountains, a possible relic of colder climates of the Pleistocene, having found shelter in the cooler environment of the caves. With, what now seems to be unavoidable global climate change, and an already well-documented warming up of southern Africa, I fear that its days are numbered. But, luckily, today cave katydids are doing very well. Jen and I found them to be thriving; I even found an additional, small cave where I had not seen them before.
We climbed back down safely and stopped at a little gift shop at Sandrifft, the highest vineyard in Africa and the legal owner of the Wolfberg caves, and picked up a few bottles to toast to the survival of K.H. Barnard’s incidental discovery, the result of his random collecting that lead to the description of the world’s only cave-dwelling katydid and now, with its proclamation as an Endangered species, its increased protection. If the chances of the katydids’ survival are in any way related to the amount of toasting, they will be just fine.
We climbed deeper into the cave, approaching a site of a Mayan ritual. Here – Abel, our half Mayan guide explained – in this pitch-black underground chamber in one of Belize’s countless limestone caves, ancient Mayans performed gruesome bloodletting rituals, slicing women’s tongues and men’s genitals to entice gods to relieve dry, parched fields with life-giving rains. He pointed to razor-thin slivers of obsidian laying among shards of broken clay pots. In the light of my headlamp I could see a few piles of ash that looked as if the fire went out only a few hours ago, but in fact they had burned hundreds, perhaps over a thousand years before I was born, and the complete lack of air movement, or any other disturbance, preserved them perfectly.
The blood rituals seemed to work, and rains came back every year. Why the Mayans thought that the gods would get a kick out of people injuring themselves is a mystery (I guess gods all over the world have similar tastes.) But, as it turns out, the Mayan self-mutilation might have been for nothing because another creature was already working on their behalf, calling to Chaac, the Mayan god of rain.
Uo, as the rain-calling animal is known among the Mayans, an onomatopoeic name based on its strange courtship song, is a frog. But it is difficult to tell by just looking at it as it is a frog like no other. When I saw it for the first time it took me a second to make sense of the fist-sized black and red balloon with short, stubby legs. It seemed that an animal like this could not possibly be able to walk, but in fact these frogs are remarkably agile and can even jump. But what it is really good at is digging.
Uo, or the Mexican burrowing toad (Rhinophrynus dorsalis), as it is known among herpetologists, is the only member of a relatively basal (“primitive”) family of amphibians, the Rhinophrynidae. Its closest living relatives are equally strange, strictly aquatic clawed frogs of South America and Africa (Pipidae). Rhinophrynus are found in low laying forests from the southernmost tip of Texas to Costa Rica. Among frogs they are unique in having their tongue attached to the back of the mouth the way we, mammals, do – in all other frogs the tongue is attached at the tip, and is flipped forward and upside-down when hunting.
Looking at the face of this animal it is difficult to see any resemblance to a typical frog. Uo’s mouth is tiny and surrounded by strange cushion-like pads. Electron microphotography revealed that every single cell around the mouth of the frog is armed with a keratinous spike, which likely protects the mouth when the frog pushes forward through the soil. Like most fossorial frogs, uo buries itself backward, using its short but powerful hind legs as shovels. It also inflates its body rhythmically as it goes deeper into the soil to widen and stabilize the sides of the burrow. But once fully dug in, the frog can move forward, pushing its snout towards termite and ant colonies, the source of its food. Apparently nobody has ever seen uo feeding, as it all happens underground, but it seems that it hunts by sliding the tongue along special grooves in its toothless mouth and swallows the prey – stinging ants and biting termites – alive and whole. To minimize the effect of the aggressive insects, the esophageal lining has leaflike projections that vastly accelerate food digestion.
When I was in Belize last week, teaching photography at BugShot, it was clear that the rain god Chaac had already heard the call of uo, and was very generously spilling his rain-filled gourds onto the earth. After a few days my black backpack turned moldy white, and my laptop flickered and died. Mosquitos seemed to target mostly the corners of my eyes and deposited several botfly larvae onto my skin, but seeing the amazing uo made it all worthwhile.
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).
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.
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 wasps and plokiophilid bugs, 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.
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.