Here’s Why thought we remembered something about spiders plucking webs to attract other spiders. We also thought we noticed that selections of Johann Sebastian Bach‘s music transcribed for guitar were in fact drawing the little creatures out from behind the bookcase to wriggle and bounce on the wall.

Could that be true? Well … sort of. We went on another Spider Quest to find out.

First of all, we looked at the spider page fom The Animal Communication Project by Washington State science writer Stephen Hart. (Check this out! He writes about everything from octopi to elephants, dragonflies to bats.).

Mr. Hart explains that certain boy spiders pluck “notes” on the web-strands of girl spiders, so the girl can tell that her date – not her dinner – has arrived. It’s a bit like strumming a guitar outside her window. How romantic!

It’s not all sweetness, though. We also found an amazing video from Arkive: Images of Life on Earth

of a female spider declaring her intent to take over an existing web by plucking the strands of the web’s owner. If you are uncomfortable with spider closeups, you might want to skip this one. But if you are fascinated by the beauty and elegance of arachnids, then by all means you should see this.

For more information, we contacted Rod Crawford, our favorite arachnologist and the curator of arachnids at the Burke Museum in Seattle. His Spider Myths website is a fascinating (sometimes very funny!) look at the things we should not believe about spiders. You might want to look at his Spider Collector’s Journal as well.

Here’s what Mr. Crawford says about musical spiders in a Q&A via email:

Here’s Why: I really have seen house spiders bouncing (as if doing pushups) on my walls when I’ve played classical guitar music (particularly J.S. Bach) on my stereo. Am I imagining this, or are they actually enjoying it?

Rod Crawford: “Enjoy” wouldn’t be the right word, since they don’t actually have enough brain cells to feel human-like emotions. But if your stereo has enough of a woofer to send vibrations through the floor and walls, spiders would certainly feel that and react in their automatic, robot-like fashion. If any of the tones mimic the pitch of a fly’s wing vibrations, some spiders could detect that through the air as well.

HW: Would certain rhythms mimic the vibrations of prey or of a mate, or do spiders just like to dance on the walls?

RC: Some certainly could mimic prey vibrations. Nobody has made enough studies of the pitch of house spider stridulations to be able to tell if musical pitches could mimic those, but it’s possible. Spiders don’t actually “like” or “dislike” in our sense.

HW: If male spiders pluck “notes” on web strands, is there an actual music to it? Has anyone heard or recorded the sound of this plucking?

RC: To my knowledge, there has been little if any acoustical study of the plucking and stridulation of web-making spiders. One research group has studied wolf spider stridulation extensively (wolf spiders make no webs, so no plucking is involved) and I’ve heard some of their amplified recordings – you might even be able to locate a sound file online, though I have no link handy. A few species have even been discovered by differences in stridulation. One of my colleagues once wanted to name a new species “harleydavidsoni” after its sound, but this noble ambition was quashed by a humorless administrator.

HW: Could a spider actually “like” classical guitar music? Could it “disllike,” so to speak, heavy metal?

RC: Not in those terms, but there could be differences in reaction depending on what realm of spider behavior was evoked by the specific vibes: prey capture, mating, fighting, predator avoidance, etc.

HW: Are there any sounds that they particularly “like” or “dislike”?

RC: I just answered this.

HW: Would certain kinds of music or vibrations scare spiders away (as opposed to grabbing the bug spray or a large shoe)?

RC: Fear, an emotion of us big vertebrate mammals, is not part of the spider’s mental universe. A vibration (such as human footsteps) that denotes an object too big to prey on, frequently evokes some sort of predator avoidance behavior. However, that is just as likely to be freezing-in-place as running-away. Also, spiders (particularly short-sighted indoor species) can’t easily tell the direction vibrations are coming from. They are not detecting these vibrations with ears, but with certain specialized hairs, which are non-directional. If they run, they are as likely to run toward as away from the source. Some run toward the nearest shadow (they can see shadows, but not images). That shadow might be yours! Of course if they could actually see you they’d likely run the other way.

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Mr. Crawford also adds one more interesting facet to spider communication, caled “stridulation”:

RC: [ Note from HW: We emailed Mr. Crawford about our intentions of writing a web plucking post] I would have liked to see whether you discussed spider stridulation (which is even more prevalent than web-plucking). Lots of spiders – in a moist north temperate zone environment, perhaps as many as 40% – can produce sounds as a means of communication (mostly with potential mates) but only in very few is there any chance of a human hearing these sounds without amplification.

You probably already know how crickets stridulate, but in case you don’t, here’s a nice article from the Scarabs web site http://crawford.tardigrade.net/bugs/BugofMonth31.html Similarly, spiders that stridulate have a file on one body part and a scraper on another. The Linyphiidae (sheetweb weavers and microspiders, maybe 35% of the entire U.S. spider species list) have a file on the sides of the chelicerae (jaws) and a scraper at the base of the pedipalps. Some also have a separate apparatus with a file on the book lung covers (underside of abdomen) and a scraper at the base of the 4th legs. Spiders in various families have a file on the back end of the carapace and a scraper on the front end of the abdomen.

There are other possible variants that are less common. Even images of spider stridulatory files are scarce online, but I found one: http://jeb.biologists.org/cgi/content-nw/full/209/6/1074/FIG6

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So isn’t this fascinating? Now we know that spiders don’t only pluck to serenade, some also do a kind of violin thing as well!

As for “dancing spiders” – it sounds as if Here’s Why simply has a good imagination.

Again, many thanks to Here’s Why‘s arachnologist of choice, the generous Rod Crawford for his time and his detailed answers. Please do check Mr. Crawford’s Spider Myths website and his arachnology section at the Burke Museum’s website for some more captivating spider information.

ADDENDUM Sept. 8, 2010: Read the Burke Museum’s post on house spiders and why we shouldn’t be scared of them, with more information from Mr. Crawford.

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