NEW YORK CITY—If spiders send chills down your spine, then it's probably best if you don't go anywhere near the American Museum of Natural History in New York. Not only are spiders on prominent display on the inside, but the front arch of the main entrance is now dominated by a giant, inflatable spider.
Of course, the people behind the exhibit would tell you that if spiders give you the chills, there's no better place for you than inside the exhibit. There, amidst a fantastic collection of tarantulas and orb weavers, you can get a far better sense of just how spectacular these animals can be—and why they actually do most of us more good than harm.
People tend to assume spiders are insects, but they're actually of an independent lineage that dates back 300 million years, making us mammals look like youngsters. The exhibit itself includes a spider fossil that is about 100 million years old. There are now at least 43,000 distinct spider species recognized, and estimates are that we've only identified about half of them.
There are a number of characteristics that distinguish spiders from insects. Unlike insects, spiders don't have compound eyes, but have a single lens covering a simple eye. Most spiders have eight of them, rather than the two that are typical of insects. Spiders also have eight legs, although it doesn't always look like they do. The reason is that they have two structures called pedipalps that often look a lot like legs, but are thought to be modified mouth parts.
Pedipalps serve a variety of purposes. On many species, they have a collection of sensory organs which help the spider sample its environment. In a lot of these species, the males also use their pedipalps to hand sperm to females during mating. Then there are the scorpions. In this branch of the arachnids, the pedipalps have evolved into the large claws that are one of the defining features of the group.
As if eight eyes and eight legs weren't enough to freak people out, most spiders come equipped with serious looking fangs, again derived from their mouth parts. These are used to inject prey with venom that generally paralyzes it. On occasion, this venom can do serious damage to humans. But, as exhibit curator (and resident spider expert) Norman Platnick said, spiders have spent millions of years evolving the ability to paralyze insects. The fact that the venom can sometimes harm other types of animals is purely "an accident of chemistry." Most spiders (including many large ones) can't generate enough force to break the skin. And, in general, spiders tend to get out of humans' way whenever possible.
There's a pretty simple reason for the lack of force in a typical spider: an average species is only a few millimeters long. Platnick, in fact, studies the goblin spiders, which are even smaller than the average arachnid. That, of course, makes finding samples and identifying species quite a bit harder. To get a good look at goblin spiders, Platnick's group often turns to the Museum's electron microscopy facility.
The other thing that tends to make people nervous is the spider webs. Not all species make webs—many are ambush predators—but the webs themselves are often spectacular feats of engineering, with different kinds of silk used for different purposes.
Another reason that we might want to appreciate spiders instead of fearing them comes down to their prey. Outside of vertebrates, they are the most significant insect predator out there and, through sheer numbers, consume huge quantities of insects. That makes them a major source of pest control.
The exhibit itself contains a wide variety of species, many of them with spectacular coloring, as you can easily see above. In the center of the exhibit, a projection system is used to let one of the museum employees do live demos, ranging from the shed cuticle of a goliath bird-eater to showing off a live spider. The text accompanying the exhibits is nicely laid out, and a few of the facts it conveyed were real surprises to me.
These include the existence of the African funnel web spider, which group together and produce a web collectively. Or the pirate spider, who pokes at the webs of other spiders, and then eats them when they approach. Or the fishing spider (one of them is on display), which uses its legs to sense ripples on the surface of some water that identify prey within.
And then there's the spiders themselves. The emphasis is clearly on the large and visually arresting, and the animals are spectacular. In the case of the two orb weavers on display, the museum has had them in the cage long enough for them to put up a spectacular web to display their craft.