Eight Legs, Two Segments
BY ALPER ÖZKAN (MSN/PhD I)
As you have probably noticed, this week's column is about spiders, so those of you who are spider-averse should probably not read any further.
The most recognizable arachnids this side of scorpions, spiders are not exactly what you'd call varied in form - owing to the lack of endoparasitic species in the group, you can pretty much identify all spiders right away as spiders, which is more than you can do for almost any other invertebrate group out there (just do a Google image search for Sacculina, Acanthocephala or Myxobolus and try to guess what sort of animals they are!). But much like crabs, spiders are extremely good at what they do within the boundaries of their core body plan, and are some of the most successful terrestrial arthropods out there. (As an aside, crabs have such a solid design that many distantly related animals have evolved to look like them!) Predators through and through, few spiders are known to eat plant matter (with Bagheera kiplingi a notable exception; however, other spiders are also known to imbibe nectar), and many are specialized in their hunting methods, for maximal capture efficiency with minimal effort.
Bolas spiders are one such example, with a unique and unusual capture method specialized to target moths. Doing away with the inefficient business of weaving many strands to capture but few insects, these arachnids hunt with only a bolas - a single strand of web with a small silken sphere on the end, which they drop down from a suitable perch. The droplet of silk contains pheromones mimicking those of female moths, so the males seeking a prospective mate fly straight into the spider's single thread and are promptly captured (though the spider is an expert at swinging the bolas around and will bring down most other flying insects as well). Other spiders don't even bother with the webbing: they merely release the aforementioned pheromones and wait with their front legs ready to grab any unfortunate moth from the air. A somewhat similar method is exhibited by net-casting spiders, which, as their name should suggest, produce a small basket of web with which they expertly net their prey, like eight-legged Roman retiarii.
The predator defenses of spiders are just as interesting as their behavior as predators themselves. The archetypal enemies of spiders are no doubt wasps -- while a large variety of animals prey on spiders, wasps are particularly famous for the fact that they paralyze the spider victim and lay their eggs within its body, leaving the poor arachnid to be eaten alive by their larvae (but then, wasps target many other arthropods in the same manner and are extremely well-equipped for the job, some even possessing the capability to inject a symbiotic virus into their caterpillar hosts to disable their immune systems). The desert spider Araneus rota, a close relative of the common garden spider, has found a way to avoid its mortal enemy, however: when confronted with a wasp with less-than-honest intents, it moves its legs closer to its body, turns itself into a wheel and starts rolling across the sand dunes, hopefully getting any pursuers off its tail before turning into a spider once more and going back to its own business. Cyclocosmia, a genus of trapdoor spiders, possesses another curious method for wasp defense: these spiders have an abdomen that ends in a hard, flat disc, so that when threatened, they can retreat back into their tunnels and plug the entrance with this platform, completely blocking any entry.
Such well-established defenses against wasps are not unwarranted. Not only are many wasps exceedingly competent specialist hunters of spiders: some have even mastered the art of spider programming. The Costa Rican wasp Hymenoepimecis argyraphaga, like many other wasps, lays its eggs in immobilized spiders, which are then left to wander around and do what spiders are supposed to do. But when the wasp's larva is about to pupate, it induces a change in the spider's behavior: instead of building its normal, insect-capturing web, the spider is manipulated to create a thick overhead web that serves as a shelter against rain, to which the pupa would be vulnerable. With its rain problem resolved, the larva is then free to kill the spider, emerge from it and pupate.
And while I'm on the topic of spiders, I might as well mention sea spiders. They are not closely related to their terrestrial counterparts and are named thus merely due to physical similarities, though their phylogeny is something of a mystery and a potential affinity has been suggested with almost every arthropod group out there. Nowadays they're considered chelicerates, along with spiders, scorpions, horseshoe crabs and their kin (but especially curious is the suggestion that they were derived from the great appendage arthropods that once swam and crawled in the Cambrian sea). Members of this group can be significantly larger than spiders (with a leg span of up to 90cm), though most are about the same size. Particularly notable is the fact
that compared to their spindly, many-jointed appendages, which
may number between 8 and 12,
their bodies are so small that most
of their organs have relocated into the legs.
r during the summer months might chance upon the Hyakki Yako, a parade of demons who gather not for any higher purpose, but just to make merry, though mortals they encounter are still doomed to die on the spot.
The 18 months of the Aztec solar calendar, each with 20 days, ended with a calibration period of five days called the Nemontemi, an unlucky period when the divine order was out of place and supernatural dangers were not unexpected. Such was the threat posed by those days that the Aztecs ignored their existence whenever possible, for to recognize them was to increase their power.
And so on, and so forth.
Halloween, though, was not one of these ominous occasions, at least not initially. Its origin is said to lie in Samhain, a festival in which the dead were honored and a good harvest was celebrated, and like the Walpurgisnacht, it was gradually transformed into what it is now. But that's not my concern, because after using Halloween as an excuse to fill half of this week's column with trivia (but then, that's what this column is for, so I'll consider this a success), I'm going to tell you the origin of those goofy carved pumpkins with goofy carved faces.
As the story goes, an old drunkard, who went by the name of Jack, had such a bad reputation that even the Devil himself caught wind of it and decided to personally determine whether or not old Jack lived up to the rumors. Jack, for his part, immediately recognized the infernal prince and knew that his time was up, though he had one more trick up his sleeve: he asked the Devil to treat him to a last drink of ale before his eternal damnation. Never missing out on a chance to get a sinner to sin more, the Devil gladly agreed.
After drinking to his heart's content in a nearby pub, Jack then demanded that his demonic patron pay the tab, suggesting an additional con: Jack would pay for his booze with the Devil himself, transformed into a silver coin, and the latter would then escape back into his original form, leaving the bartender penniless. Impressed by Jack's keen wit even at death's door, the Devil gladly complied, only to find himself in Jack's pocket, where a crucifix was also kept. Unable to transform back, the Devil was then forced to give Jack an extra ten years of life in return for his freedom.
At the end of the ten years, the Devil returned to take Jack's soul once and for all, no doubt with tortures devised just for him as payback for the earlier humiliation. Willing to accept his fate, Jack this time asked for one last apple to eat, and the Devil agreed again - after all, there were no transformations involved, and the chance for trickery seemed very low. But apparently not low enough, for while the Devil was busy climbing a nearby apple tree, old Jack covered the tree's trunk with crosses, again trapping the poor infernal prince (for all his unholy might, the Devil apparently can't fly). Jack's demand was heftier this time - he asked for his soul never to be taken to Hell - but the Devil had no choice but to agree.
As the fates would have it, Jack soon succumbed to old age and his drinking habit, and made his way to Heaven to enjoy his afterlife -
only to be turned away at the gates, for he was a sinner. Having no other choice, he then tried his luck at getting into Hell, but the Devil couldn't break his word and had to refuse entry. In grudging recognition of Jack's trickery, the Devil instead provided him with the undying fires of Hell in a lantern to assist him in finding his way on Earth, where he is now forced to eternally wander, barred from both Heaven and Hell. Imitations of this lantern - initially carved in a turnip but later upgraded to a pumpkin - are what you see decorating houses and gardens every Halloween.