Friday arachnid (etc.) blogging: multi-legged mambo italiano

Before we get started, here's one jumping spider who has been waiting since May to appear on the web:

The stone railing you're looking at is on the Costiera amalfitana in southern Italy, which gives this post its theme. For the pictures below the fold are our holiday snaps from Italy (albeit farther north and from late August-early September). More than just spiders this time, today's FAB boasts stars from three great phyla, including our own. It's been a long time since I posted any Friday arachnids (as David Duff complains in comments to Tuesday's post), so as compensation you are getting a good many creatures today; those with slow connections might want to wait till they are at a computer with broadband access before going on.

We'll start with a spider, of course.

Now there's a pretty face. She shouldn't be hiding it bashfully behind her hand like that. (BTW, I have altered this photo by flipping it 180°. She's used to hanging upside down. You might not be, and turning the photo round will help you see her 'normally'.) We stared at each other for a while before I snapped the picture. That is, I stared at her; she stared at the tip of my nose, which would have been the bit of me closest to her.

It's an unanswered (and perhaps largely unanswerable) question whether and to what extent animals -- especially animals as little related to us and as relatively simple as spiders and other small arthropods -- are 'conscious'. Certainly they perceive, and some of their senses are so acute as to beggar belief. (Sight is not one of those senses, though, at least not in most spiders.) But do they conceive, and if so how?

If they are conscious at all, though, it's a safe bet spiders are not conscious of us as biological units. We're simply too big. If they are aware of a human, what they are aware of is the fingertip (or, all too often, the rapidly descending shoe sole) moving towards them. When your fingertip is in their range of vision, much of the rest of you is well beyond it. Perhaps it's good their brains are so tiny. Had they humanlike imagination, surely they'd be racked with terror at the thought of us, stupendously huge lumbering dangerous giants that we are. Bear that in mind next time you shrink back at a sudden flurry of tiny legs, shrieking 'Eeek! A spider!'

But all this philosophising is too much for our wee friend, who retires to her hideaway to consume a small moth she'd caught earlier.

This brute, by contrast, is far too big to be a meal for such a very small orbweaver:

He is a stag beetle of the genus Lucanus, a touch over 5cm in length. That's not especially impressive by stag-beetle standards; specimens of L. cervus (which is what I suspect this fellow is) can easily reach 7.5cm. Still, I am sure he is the biggest beetle I have ever picked up.

The beetle's thumping great jaws, by the way, are not for tearing gobbets of flesh from prey. These beetles feed by sipping daintily at tree-sap. The jaws are for males to use in rassling other males to see who gets the girl.

Though both belong to the great Phylum Arthropoda, the jointed-limbed animals, spiders and beetles aren't terribly close relatives. Compared with our next guest, though, they are kissing cousins. For that matter, even we are the beetle's kissing cousins by comparison.

This is a jellyfish, from the Phylum Cnidaria, the 'nettled ones' or, less poetically, stingers. And that is what they do, using nematocysts, specialised cells that are like a microscopic jack-in-the-box, only with a tiny venomous hypodermic harpoon inside instead of an evil-looking clown.

Cnidarians have no brains. Indeed, they have no head to keep one in. They are not bilaterally symmetrical like spiders, beetles and your own good self. Some of them live bizarre communal lives that make ants seem libertarian loners by comparison. Phylum Cnidaria includes animals most people have heard of, even though most will never encounter them: hydras; Portuguese men-of-war; corals; sea anemones; Australia's infamous box jelly, the 'sea wasp', with its unusually well-developed (for such a 'primitive' creature) eyes and its horrific sting. Best known of all cnidarians, though, and the ones you are most like to run across outside the aquarium, are the 'true' jellyfish, the Scyphozoa.

Lots of coasts are plagued by (often seasonal) jellyfish infestations. I have been fishing off Long Island, New York, where the water just below the surface was stuffed with jellies: at least one per cubic metre, each a bit smaller than your hand. I'm told that they don't often go all the way in to the shore, but can at some times of year, where they leave unlucky swimmers with an irritating but not particularly dangerous sting. The Costa degli Etruschi had its own jellyfish plague while we were there, though these stayed well away from the beach (they were at least a couple of hundred metres out, where we saw some swimming a little below the surface while we were kayaking). However, large numbers of dead or dying jellies were washed ashore. I don't know whether this is seasonal or had something to do with the weather. (Though the weather was fine much of the time, we did have some rain and high winds at night, and one enormous two-day storm at the beginning of our stay.) I didn't hear of anybody being stung, and the locals didn't seem concerned at the many meduse, as they are called in Italian.

Indeed I am not sure these jellyfish can sting. They ranged from about 18cm-24cm across the 'bell' and were mostly translucent, but for a dark blue ring round their rim. They look like Rhizostomae, which lack the long hairlike stinging tentacles of other jellies. In any event I accidentally brushed a bare foot against the tentacles of the one in the photo, and felt nothing unpleasant. I have read that all cnidarians have nematocysts; I do not know whether the Rhizostomae have lost theirs secondarily, whether their 'harpoons' are too small to sting a human, or whether the stingers of dead jellyfish simply don't work. (That last is a bit doubtful, actually, as some octopuses reportedly break off jellyfish tentacles to use as weapons.)

But hello, what's this?

There; do you see it? That brief white flash at the jelly's edge... and, quick as a wink, it's gone again.

It'll be back, though. It's a very small crab (crabs are crustaceans, which like insects and arachnids are one of the great arthropod subgroups). And it's nibbling at the dead jellyfish -- one of those 'circle of life' things. The crab was very cautious, and very fast. With its small size, it can obviously treat the saturated sand of the surface as a fluid, 'swimming' in it as easily as you or I would swim in a pool. A quick shear with the claws, and down it plunges, only to resurface a few seconds later for another bite.

It wasn't reckoning with me and my stick, though, and found itself flipped up the beach onto packed dry sand. It tried to scuttle sideways (as one does, if one is a crab) down to the water, so I flipped it again. This time it landed on its back and played dead. Interesting. I flipped it a few more times, and it always did the same: land right-way up, scuttle towards the water; land upside-down, lie still. I picked it up and took it home to the kids, pausing to dunk it in the water every hundred metres or so. My daughter was delighted:

The greenish-greyish mottling of her carapace is very effective camouflage in wet sand. The crab almost never needs this, though. We put it into a large clear plastic cup filled with seawater and some sand at the bottom. Straightaway it buried itself. All one could see (and then only if one knew where to look, and looked very carefully) were two tiny eyes, each like a grain of sand on a stalk.

Let's turn now to a 'crab' of a different sort, a Thomisid crab spider.

She's very tiny - about the size of a lower-case 'o' in this text, assuming you are looking at it in 1024 X 768 resolution. (I write 'she', BTW, though I cannot tell for sure. Given its tiny size, this spider is almost certainly immature. The pedipalp visible in the picture looks like a female's, but for all I know an early-instar male's might look much the same, gaining its characteristic 'boxing-glove' appearance only after further moults.) A crab spider is no more closely related to a true crab than is a great hairy tarantula, of course. But even though the photo can't recreate the spider's scuttling movements, it shows you how apt the popular name of these creatures is. Note how very small her chelicerae ('jaws') are. These are the two bits just beneath her 'face' and next to the visible pedipalp. The fangs at their ends are even tinier. Crab spiders are among those spiders that couldn't bite a human if they wanted to (most spiders never want to anyway). Her chelicerae even lack the jagged 'teeth' along their edges that many spiders' have, meaning she cannot chomp up her prey. She can only sip the liquefied innards out through the minuscule holes made by her fangs, leaving the prey's exoskeleton intact.

Here's another tiny and quite clearly immature spider. She is so young I am not even certain what sort she is.

From the general habitus and markings, though, I'd say she's probably an araneid (orbweaver). In any event, she is certainly... a SPIDER BABY!

Ted:      A spider baby?
Dougal:  It has the body of a spider but it's actually a baby.
Ted:      ... does it wear a nappy?
Dougal:  No...
Ted:      Well, does it have the head of a baby?
Dougal:  No.
Ted:      Then how do you know that it's not actually just a spider?
Dougal:  They keep it in a pram.

Erm... sorry, couldn't resist. At least you were spared the Tunnel of Goats. Anyway, to get an idea of the spider baby's scale, you can look at my daughter's string bracelets, which are the same as in the photo of the crab above (same daughter too, for that matter).

This great bruiser, though, is anything but dainty:

He's a male gnaphosid, or flat-bellied spider. Gnaphosids don't trap their prey in webs. They are hunters, but unlike the sharp-eyed salticids (jumping spiders) are mostly nocturnal, and their sight is hardly better than that of the hopelessly myopic orbweavers. Instead they hunt by feel, sensing vibrations around them and pulling down anything they stumble upon than cannot kill them first. Our specimen might possibly be immature, but if so is closer to maturity than the crab spider above. You can easily see the 'boxing gloves' at the ends of his pedipalps, even though he is not 'aroused'. (When he is, the 'gloves' will swell and expand to their full and, for each species, uniquely baroque shape.) He looks to be closely related to the Balearic gnaphosid who starred in an earlier FAB; perhaps even of the same species. Our lad would be about a centimetre in length, not counting legs or chelicerae, and like many gnaphosids is powerfully built. (The female from the earlier FAB would have made short work of him, though.)

Now here is a story with an unhappy ending (for at least one of the parties, anyway). You've probably seen insects like this one before:

It's an ensiferan, a grasshopper of the sort commonly called a 'katydid' and part of the same group that contains crickets. This one found its way to a table on our balcony. We'd just had coffee; the hopper found a couple of stray grains of sugar and lapped them up greedily. (I'd never heard of grasshoppers eating sugar before, but why not? They'll eat most anything; some of them even eat other grasshoppers.) Here she is scouting round for more. Hmmm, I thought, if she's hungry and has a sweet tooth... So I put her on a small plate and gave her a piece of one of the biscuits we'd been having with our coffee. Sure enough, she began chomping happily away. Then we went out and didn't return till the evening...

... and when we did return, there she was still, standing guard over her treasure-trove of biscuity goodness. She had gnawed away quite a visible chunk of it, too. A strange thing, though: there wasn't a trace of frass (if that is the correct technical term for grasshopper shit) to be seen. What happened the next day suggested an explanation for this curious absence.

That morning my daughter found the grasshopper prostrate on the balcony. She thought it was dead. It wasn't; at least not quite, not yet. She put it on the balcony's railing to have better light. The hopper just lay on its side, an antenna occasionally twitching. And then, after a while, a fat wee maggot emerged from the hopper's body; Alien in miniature. (Clearly the maggot wished to go elsewhere to pupate, as opposed to using the 'mummy' of its victim as a shelter, as may other parasitoids do.) Alas, a stiff breeze carried the maggot away before we could capture it. The same breeze also carried away the now-empty husk that had been the hopper.

Lots of people know that many wasps are parasitoids. And it's true that a great many hymenopterans are parasitoids, and that they account for the largest group of parasitoid insects. (Even bees, those vegetarians of the hymenopteran world, probably had parasitoid ancestors.) What lots of people don't know is that the Diptera -- flies, in other words -- account for most of the other known parasitoid insect species. And I think it was a fly that killed this hopper. There are tachinid flies that parasitise the katydid's cousins, crickets, attracted by their mating call. I shall have to look in Godfray to see whether there any suggestions about what insect killed our grasshopper, but I suppose we'll never know for certain.

Here is another katydid, so far as I know luckier than her relative:

She is running around at night. To my knowledge katydids are diurnal. But our balcony had a strange feature -- a large, bright light that could not be turned off. The light attracted many night insects (and things looking to eat them). But it also confused a lot of day insects caught in its glare come nightfall. This is likely what happened to the katydid in the picture.

They are very pretty, this species -- bright green with tiny red flecks; red eyes with, as you can see if you look closely, subtle brown stripes. Those black dots on the eyes aren't pupils, by the way. They're an optical illusion. The black dot you think you see is the patch of lenses on the insect's compound eye that you are looking straight down at. Those lenses you are seeing at an angle have their 'normal' appearance. As you shift the angle at which you view the insect, the black dot naturally shifts as well, creating an eerily pupil-like effect. This doesn't happen with all insects, but it does with many hoppers as well as with mantises.

While we're at it, let's have a closer look at the insect's face:

Do those mouth-parts remind you of little legs? They should, because that's more or less what they are. When we speak of an insect's or spider's mouth or jaws, we speak with perfect precision if we are thinking in terms of function. These bits do exactly the same job for a katydid or black widow that they do for us. But if we are thinking in terms of structure and origin, to speak of an insect's 'mouth' or a spider's 'jaws' is but broad analogy. Our jaws evolved from gill arches. Arthropod 'jaws' evolved from limbs. The postulated common ancestor of all arthropods was a segmented, wormlike creature whose segments bore appendages. As its descendants developed and diverged, some of these segments became legs, while others became 'mouth' parts. Still others became antennae or pedipalps or spinnerets or what have you. (To further complicate matters, other sorts of appendages served as 'gills' and, in lots of arthropods, still do.)

Our first arthropod today was a spider. Our last is a spider's worst nightmare:

It's a wasp, of course. And I am pretty sure she is a pompilid. (No idea what she is beyond that; those white bands on her antennae might be a clue for those who know more about hymenoptera than I do.) Pompilids are a group of wasps that hunt spiders. The pompilids include Pepsis, the famous 'tarantula hawk', an astoundingly big wasp of the American southwest that hunts even bigger tarantulas. (Pepsis, BTW, is reputed to have the most agonising sting of any insect. How do they get volunteers for those studies, I wonder?) Her cousin (as I suppose her to be) in the photo is much smaller, about 2.5cm in body length. I know little about wasps, but am guessing she is a pompilid based on general appearance, including her curly antennae and those long hind legs. I'm also guessing it based on this:

Here she is, invading a spider's (empty) sheltering-web. She didn't just stumble into it. She was walking around, seemingly purposefully, waving her antennae ('sniffing', as it were) and acted as though she knew just what she was doing. Alas for the wasp (but lucky for the owner of that sheltering-web), she was, like the katydid, the victim of our balcony-light. Being a pompilid wasp would seem to be a daylight job; her intended prey works nights, and was out on the job when she called.

The spider should be grateful for that. A pompilid paralyses a spider with a sting, then carries it off to provision the nest she digs for her larva. Sometimes she'll snip off the spider's legs first (the spider won't be using them anymore). Then she puts the spider into the nest and lays an egg on it. The larva hatches and slowly eats the spider alive. The spider is unable to move and can do nothing to escape its fate. I wondered up above whether spiders are conscious. Perhaps it is for the best if they are not.

Mind you, this wasp might be a sphecid rather than a pompilid. Not all sphecids hunt spiders, though this one (if sphecid she be) seems to. If she is a sphecid, her spider victims might have the consolation of being entombed alive in very prettily proportioned wee mudpots to await their doom, for the sphecids include the 'potter' wasps.

Our final animal is a member of Phylum Chordata, just like you. She's a toad, and though she is not a gorgeous jewel like some tropical rainforest frogs, by toad standards she is rather pretty.

She also has an interesting defence mechanism. When (for example) picked up by an excited child and held up for a parent to look at, the toad pisses. Pisses voluminously -- more piss than one would have thought a toad that size could ever possibly contain -- and all over the place, especially on the parent's feet, as any parent who happened to be wearing very flimsy open sandals at the time would be in a position to report.

So much for our Italian arachnids (etc.), then. I'm sure you'll agree with me that they are (like most things Italian) admirably attractive and stylish. I shall try to be a bit more regular in posting instalments of FAB but, for the time being, it's going to have to be the dour and stolid arachnids (etc.) of Germany.