Sunday, 23 October 2016

Webspinner

Image: Mike Quinn
Spiderman. He just doesn't make sense!

It's not the whole 'bitten by a radioactive spider and now he's a bit like a spider' thing. That's fine. That's great. That makes perfect sense. Well known fact, that is. The problem is the 'now he's a bit like a spider'.

Is he? Is he, really?

Image: Ken-ichi Ueda
Female Webspinner
If he's so much like a spider then where are his extra legs? His extra eyes? Why doesn't he have silk coming out of his backside? How come he isn't physically surprisingly weak, relying instead on his venomous bite? How come he runs around all the time instead of being content doing absolutely nothing for absolutely ages.

No, Peter Parker, that was no spider. That was a Webspinner.

It's an easy mistake to make. Sort of. A lot of people blame spiders for things they didn't do. These days pretty much everyone gets bitten by a mysterious, villainous entity or malignant force known only as 'brown recluse spider'. These so-called 'spiders' come in many forms, including bacterial infections, fungal infections and bedbugs. Usually no spider is ever found, just its calling card, a painful and unsightly skin disorder that the victim should really see a doctor about.

Image: chan.ethan.5
Male Webspinner. Possibly radioactive
Even if ol' Pete had seen the culprit with his own eyes it's quite likely he'd have no idea what he was looking at. Webspinners are very much on the lesser-known side of the insect world. Even the scientists who study them have trouble figuring them out!

It's not that they're particularly rare. Several hundred species of Webspinner have been described so far, making up their very own order called Embiidina or Embioptera. Their true home is the tropics, though enough species can tolerate a bit of chilly weather that every continent but Antarctica has at least a few.

Image: Don Loarie
Thing is, while about 400 species have been described, there are a lot more than that in the actual world. One researcher reckons he has 1,500 undescribed species in his own collection! Incidentally, that must be one of the coolest things about being an insect scientist. You can have draws full of specimens to admire in your own home. People might think you're a little odd but at least you're not the guy with a collection of taxidermy vultures. People think that guy is a psychopath.

The problem with Webspinners is they all look so similar - a cylindrical, usually entirely brown thing, up to 2.5 cm (an inch) long, with a round head and stocky legs. Even tried and true methods like looking really closely at various intimate body parts isn't as reliable as usual in telling species apart.

Image: CSIRO
A Webspinner on a tree. But WHERE on the tree?
Scientists aren't even sure where they fit on the family tree. To me they look a lot like other insects that crawl through dark and narrow spaces, like earwigs and termites. As it turns out, most scientists today think their closest relatives are the phasmids. In other words, leaf insects and stick insects.

It sounds sort of ridiculous at first. I mean, leaf insects? Stick insects? They're the kind of animals who are so dedicated to very specific types of camouflage and mimicry that if you put them on a plain, white background they suddenly appear astonishingly ornate and eye-catching. What they don't look like is a small, brown cylinder. Well, maybe some of the smaller stick insects do, but still...


What you always have to remember is this: evolution can do remarkable things. Think about termites. They're cockroaches who acquired a bunch of friendly bacteria that let them digest wood. And then they decided to settle down to family life. Mega-family life.

So imagine something like the small, squat and rather ancient stick insects of the genus Timema. Not so extravagant. Not so leafy. Not so sticky (sticky? Stickish. Whatever). Perhaps this is what their ancestors looked like. Some of them marched among the twigs and leaves and became the flamboyantly camouflaged, fearless stick insects we know today. Another, more humble, group hid in the bark.

Image: José María Escolano
Home
And then they very quietly built themselves flamboyant web-galleries so they could be fearless in private. Which takes us to the whole web-spinning thing and yes, Webspinners spin web from their wrists! Or... front-ankles?

It's the females who do most of the work. Both male and females have enlarged front legs but the female's are even bigger, particularly around the ankles. Actually they're called tarsi, and each one is packed full of up to 150 silk-producing glands. With so much silk at her fingertips (leg-claws, I suppose), it's a simple matter for her to effortlessly construct a home composed of web-slung chambers and silk-spun tunnels.


Video: BBCWorldwide

These silk 'galleries', as they're known, cling to tree bark, burrow under rocks and delve into leaf litter. It's a safe and cosy home which keeps moisture in and keeps predators and bad weather out. Some Webspinners will even decorate it with bits of nearby detritus. Maybe 'decorate' is the wrong word. 'Hide' might be more accurate. Some of the old, stick insect's instinct for camouflage coming through, perhaps. And anyway, it's a nice, organic touch. Like a rural log cabin instead of these modern silk houses they have nowadays. And it makes it even safer and cosier.

In fact, it's all so wonderfully safe and cosy that Webspinners are loathe to ever leave home. Sometimes they have to, like when they need to find a juicy stash of moss, lichen or rotting vegetation to eat. But they don't celebrate a successful expedition with an outdoor picnic. Instead, it's back home and back to work as they build a whole new corridor to the new food source so they can eat indoors like civilised people.


Video: cmkosemen
Check out that backwards running!

As time goes by these gossamer gangways can became labyrinthine networks of narrow tunnels extending in all directions. Webspinners run around it with lively speed and confidence. That's where names like Embiidina and Embioptera comes from; embios means 'lively'. They even have a kind of spidey sense! It's in the form of a pair of tails that are so sensitive they can walk backwards just as easily as they can forwards.

Some Webspinner galleries are bigger than others. Many species are solitary, so a single female builds the whole nest and lives there with her offspring. She might even feed them, too! Can you imagine? She goes out looking for food and when she finds it she builds a whole chunk of house to it. And then she chews up some of the food in her own mouth so she can feed it to her youngsters. AND she might even have to cover up the new wing of her house in bits of detritus to hide it from nosy neighbours. It's homemaking on a whole new level.

Image: S. Dean Rider, Jr
Baby!
Some Webspinners are more social. A single nest may contain several mothers along with all their offspring. I can only hope they've developed some kind of rota system so they have at least a tiny bit of time to relax.

But that all raises the question of the males. Where are they? And how dare they?

Truth is, they're in the nest. At least the young ones are. Sitting around eating or getting fed by their devoted mother. They soon grow up, stop eating entirely and, in some species, grow wings. The wings are soft and flexible at first so they can bend as the Webspinner walks forward and back in the tunnels. They'll only be flight-worthy when he puffs them up and fills the veins with haemolymph (insect blood), and he'll only do that when he's ready to leave the nest.

Image: Dr.Jose R. Castello
And he only leaves the nest to find a new, female Webspinner to mate with. In some species the male has no wings at all so he has to go a-courting on foot. And, er, sometimes he doesn't get very far so he mates with one of his sisters. In some Webspinners the females can, if need be, produce young without mating at all, which I think is the better solution.

In any case, the male Webspinner is starving hungry so whatever the result of his endeavours he dies soon after, saddling the female with all the housemaking and homemaking. Or, occasionally, she might eat him. Which seems fair enough, to be honest. She's a got lot of work ahead of her.

Image: Dr.Jose R. Castello
So what's the tally? Wrist-mounted silk-slingers, spidey sense, running around all over the place, the fact that Spiderman can't eat with his mask on. Seems clear to me that young Parker was a little rash in his conclusions that fateful day in the power plant. That, or he just thought spiders were cooler.

And he calls himself a science whizz?

4 comments:

TexWisGirl said...

peter parker would be proud...except for the mating with his sister part, maybe...

Joseph Jameson-Gould said...

Hahaha! Yeah, maybe!

Lear's Fool said...

That backwards scuttle was awesome! I suppose that's one of those features of living in galleries, but it's still pretty cool.

Joseph Jameson-Gould said...

Yup, and they've got a real turn of speed when they want it!

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