Have Scientists Learned Anything from Giving Drugs to Spiders?
Turns out the famous 1948 experiment tells us nothing about drugs, and a whole lot about spiders.
Back in 1995, my D.A.R.E. instructor used a series of old photos in a lesson. The first was a normal spider web, then there were several webs in various states of shittiness. The explanation: the spider was on drugs when it made these webs! Surely the one high on marijuana (above) lost its train of thought partway through, and started staring at its own eight legs, I thought.
From time to time, these photos crop up again to illustrate something slightly different: since caffeine has arguably the most deleterious effect on web-building of all the drugs, the lesson of the spider webs has become less about the Horrors of Drugs has calmed down, and more about the surprisingly powerful psychoactive effects of caffeine.
"In addition to a general rule of thumb to avoid street drugs, it may also be wise to consider passing on that second cup of coffee this morning," a writer for Relevant Magazine concluded.
It may come as a surprise, then, that the original purpose behind giving spiders drugs wasn't to study the relative effects of drugs—or really to study anything. The person who did it wanted to get the spiders high for his own personal gain.
In 1948, the German zoologist Hans Peters wanted to make a documentary about spiders building webs, but couldn't because he didn't want to stay up past 2AM to watch it happen. Peters got his pharmacologist colleague Peter Witt to rig up a system for giving the spiders drugs in doses of sugar water, all in the hopes that their scrambled brains would lose track of the time, and make some webs during normal work hours.
Instead, Peters got the worst possible results: The high spiders annoyingly kept making their webs in the middle of the night, but they were also terrible at it. His photography project had to be scrapped.
But Witt was intrigued. The project became a lifelong passion for the pharmacologist, who over the decades teamed up with other likeminded scientists, including the Canadian chemist David Peakall, who took an interest in the effects the drugs were having on the business end of the spider, where the silk came out. Entomology seemingly always took a backseat.
"Chemistry wasn't nearly as advanced as it is now," said Linda Rayor, an entomologist at Cornell University who studies spider behavior. "Witt was into the idea that you could feed the blood of people on various drugs to spiders, and those spiders would build very drug-specific webs."
In addition to blood, Witt also gave spiders the urine of people with schizophrenia. There was a popular idea going around that schizophrenics had a hallucinogenic compound flowing through their veins. Some of Witt's contemporaries at a Swiss mental hospital performed a similar experiment, and found no connection between schizophrenia urine and crazy webs. Their only positive conclusion was that spiders hate the taste of schizophrenia urine. According to their report, after being dosed, the test subjects "left the web, rubbed any residual drops off on the wooden frame, only returned to the web after having given their pedipalps and mouthparts a thorough cleaning, and could scarcely be persuaded to take another drop of the stuff."
It appears Witt imagined a world where all police departments and hospitals have a sort of spider lab. When a patient or inmate behaved strangely, that person's blood would be fed to a spider, which would then be left overnight to build a web. In the morning, a careful look at the spider's handiwork would provide answers. "Aha! My webs indicate this inmate over here is a laudanum addict, and this poor patient is suffering from schizoaffective disorder," a chin-scratching lab technician might have said.
"It obviously didn't work that well," Rayor told me. "That wasn't necessarily the end-all-and-be-all in terms of analyzing what kinds of drugs people had taken." Eventually technologies like mass spectrometry made Witt's spidergraph (my word, not his) unnecessary.
But Witt's photos are still out there. Each one shows a crazy web next to the name of a drug, leaving the viewer to think that it must be a valuable lesson about the effects of drugs. But, Rayor added, "it's not particularly valuable information."
We can't really assume there's much of a connection between what a drug does to the web-building mechanisms deep in a spider's brain, and what they do to our own mammal brains. For instance, naturally occurring amounts of caffeine can kill animals that need a hormone called octopamine—a category that includes spiders, but not humans. That might help explain why caffeine devastates spider web production.
"When I'm teaching this," Raynor said, "I'm teaching about Peter Witt's experiments, which are only valuable in the context of their innate web-building behaviors." Although, she hastened to add, "biologists don't like the word 'innate.'"
But in this case, the word seems fitting. The behaviors involved in web-spinning aren't learned. Their mothers are typically dead by the time a spider is born, let alone by the time it starts building webs, meaning every young spider has to just figure it out. The spider doesn't need a Gladwellian 10,000-hour practice program either. "The first couple times, they're kind of not quite as complicated, and not quite perfect, but after the first couple times, they do a really good job," Rayor said.
So it's not so much what effect a bong hit will have on a spider web, but the fact that that bong hit will do just about the same thing to every web that's of interest to entomologists. "That the drugs modify their behavior in such a particular way is really interesting," Rayor explained. "This isn't a learned behavior."
Scientists are only beginning to understand the ways this behavior manifests in webs. Crucially, Rayor said, if there's some kind of alteration to a spider's brain chemistry, it doesn't seem to effect the spider's sense of what a web should look like.
Perhaps in orb weavers, she said, "the third leg is holding onto the spider silk as the spider moves around in very characteristic ways, and the fourth pair of legs is moving in a very characteristic ways, to pull out the silk and lay it down." It's these specific movements that are altered by a change in the spider's brain chemistry.
We can see this in an example that has nothing to do with drugs. Ichneumonoid wasps plant their larvae on the backs of spiders. At first the spider with a wasp larva living on its back acts pretty normal, Rayor said, "but as the parasitoid gets close to pupating to maturity, it somehow causes changes in the spider's brain so that the webs are built in such a way that they become a retreat for the parasitoid." Essentially the "retreat," works as a rain shelter for the wasp, which the wasp can enjoy while it eats the spider who built it.
So what horrifying mind control chemical is the wasp injecting into the spider? "I haven't seen any really good analysis," said Rayor. "This is relatively recent, that we're starting to notice this and recognize the amount that the behavior is modified." But as with the drug effects, it's likely just a few small changes in muscle movement that have a drastic change on the spider's web.
Further study into this might go a long way toward cracking one of the biggest spider-related mysteries—the one at the center of the classic children's book Charlotte's Web.
Every time the film adaptation is played on television, Rayor told me, people call entomologists at museums and universities to tell them that a spider in their garage is writing messages to them. After the entomologist has calmed the caller down, he or she explains that they're just witnessing a known spider behavior seen in diurnal orb-weavers called stabilimentum.
Also known as "web ornamentation," stabilimentum is a spider's use of its thicker silk—the stuff they wrap around their prey—to spruce up its web in a couple spots. It may look like a bunch of capital "As," "Vs," "Ms," and "Ws," but it's not a message from Charlotte that Wilbur wants his MAMA to take him to the VMAs. It's just random zigzags.
But why does a spider put zigzags in its web? There are some ideas out there, like that the more visible stabilimentum—in contrast to the relatively invisible rest of the web—help the spider attract prey, or keep predators away and help humans avoid a nasty mouthful of web.
These are all just guesses, however. Rayor cautioned me from jumping to any conclusions about a grand scheme at work in any aspect of a spider's web. "By messing with their brains, they modify things in a particular way," she said, explaining that you don't even have to get into a spider's brain chemistry to "mess with its brain."
Spiders will fix a web's radial lines (the straight ones resembling the spokes on a wheel) if you break them while the web is being built, Rayor told me. But hilariously, if you wait until they've moved on to the more intricate spiral lines, and mess up one of the radial lines, the spider will just make a weird, deformed web, rather than fix the radial lines. "They can't go back. They don't have that kind of flexibility," she said.
So it turns out, giving a spider drugs is just one possible interruption to a process within a brain that is, like all nonhuman brains, alien to us. We can't plausibly look at the handiwork of that arachnid and assume we know anything more about the drug that made it that way. Still, Rayor seemed thrilled to talk about the Witt photos, even though it sounded like she had used them as an example in a thousand lectures.
"It's a really cool example," she said.
Follow Mike Pearl on Twitter.