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Q: Cobwebs: Spiders or Dust or ? ( Answered 4 out of 5 stars,   1 Comment )
Subject: Cobwebs: Spiders or Dust or ?
Category: Science
Asked by: kitandgary-ga
List Price: $20.00
Posted: 29 May 2005 21:09 PDT
Expires: 28 Jun 2005 21:09 PDT
Question ID: 527145
Settle a dispute.  G contends that some cobwebs are made by spiders
but that others made without arachnid intervention and made of dust
held together by electrostatic attraction.   M contends that all
cobwebs are made by spiders and that cobwebs, unlike dust bunnies, are
not formed of dust.  We need a reference to a reliable scientific source.
Subject: Re: Cobwebs: Spiders or Dust or ?
Answered By: tlspiegel-ga on 29 May 2005 21:42 PDT
Rated:4 out of 5 stars
Hi kitandgary,

Thank you for an interesting question.

MadSci Network: Zoology

Where do cob webs come from?
You never see a spider in cob webs nor are there patterns present generally 
associated with a spider's weaving. Yet those dust particles can't just fall
together and span sizable distances by themselves."


Posted By: Jurgen Ziesmann, Post-docBio and EcoChem

"Cobwebs come from spiders, even if you do not see the spider. Indeed,
there are quite a number of arthropods that can produce a sort of silk
similar to that produced by spiders. For example, silkmoths or other
butterflies produce a silk that is involved in some aspect of
reproduction or development. The silk production may be used to
produce a shelter for the eggs or for the pupae, e.g.

"Cobwebs," as they are commonly known, are built by spiders. I found a
picture of a typical abandoned cobweb on the internet. Each spider
species has its own pattern of weaving. Even the more or less
irregular pattern shown on this picture is typical for the species
producing it. Some spider species do not produce webs at all - jumping
spiders, for example.

Some species build a very regular web every morning, destroying it in
the evening again. The species building the web shown in the picture
leaves its webs to trap prey, until they are covered with too much
dust for hunting. Then they abandon it and build a new one somewhere

Why do you never see a spider in it? You are too late. Fresh webs are
nearly invisible. When you see a web easily it is already covered with
dust and abandoned."


Words to the Wise - Your Etymological Queries Answered

"The word cobweb is the problem.  I know that cob is the old term for
a spider, therefore, a cobweb is a spider web.  The problem is that,
in my house (and the houses of a few other people I know), there are
cobwebs and spider webs.  A cobweb is a single strand of dust, whereas
spider webs are multi-stranded in a pattern.  I can find no term for
cobweb/spider web that is as I describe above, so I turn to you for


"You actually have the word you seek already.  Cobweb does mean
"spider web" in its earliest incarnations (14th century).  However,
less than one hundred years later it was already being used to refer
to similar material produced by insects (versus arachnids), and one
hundred years after that, it referred to "any musty accumulation".

The cobwebs to which you refer are actually single strands of spider
thread that collect dust (versus a complete spider web).  Based on the
history of meaning discussed above, you can probably get away with
calling spider webs and spider strands cobwebs, especially if they are

While we're at it, we should discuss the etymology of cobweb.  It is,
as you suggest, formed from cob "spider" and web.  Cob was originally
coppe (as in Middle English coppeweb, 1323) and later cop.  It derived
from Old English attercop "spider", which was formed from atter
"poison" and coppe "head".  Coppe is thought by some to be related to
cob "ear of corn" which would make a cob more a "head of corn".  We
don't hear other uses of cob much here in the U.S., but in Britain it
has other meanings:..."


The Straight Dope - A Staff Report by the Straight Dope Science Advisory Board

Are cobwebs made by spiders?

"What exactly are cobwebs? My mother says that they are "some kind of
dust formation." A friend of hers insists that they are dusty spider
webs and dusty strings left behind when a spider is moving about. My
mother is almost fiercely against this idea and says that no spiders
are involved. I implore you to clear this up."


"Yes, cobwebs are made by spiders. Arachnologically speaking, a
"cobweb" is a web made up of short irregular strands arranged
haphazardly, as opposed to the elegant and elaborate orb webs made by
spiders of the family Araneidae. The "cobweb spiders" make up the
family Theridiidae. One of the commonest in the U.S. is the common
house spider Achaearanea tepidariorum. Because the strands are sticky,
they gather dust, producing the long fluffy streamers you see. The
notorious black widow spider Latrodectus mactans also belongs to this
family. Another spider which may be responsible for webs around the
house is the long-legged cellar spider Pholcus phalangioides of the
family Pholcidae, which makes loose irregular webs in dark places.

Some stray strands of cobweb aren't (and never were) part of a web,
haphazard or otherwise, but are produced by spiders or other
arthropods just the same. Jumping spiders, for example, trail a
dragline wherever they go, but don't make webs. A single filament like
this can sometimes get into the airstream and land and stick
somewhere. Likewise, as readers of Charlotte's Web know, many spiders
will disperse from their egg sac by "ballooning," which involves
trailing a long filament of silk from the spinnerets until the air
currents catch hold (like flying a kite more than ballooning, I
suppose).  These filaments can obviously occur indoors if that's where
the egg sac was located, or they may blow in from the outside.
Similarly, many tree-feeding moth larvae will make silk "escape" lines
if they feel threatened, and these lines can break loose and get into
the air.

While we're on the subject, you're probably wondering what a "cob" is.
Here's what the Word Detective says:

The most commonly encountered "cob" is the corn-cob, the cylindrical
woody shoot on which grains of corn grow. That kind of "cob" comes
from a very old English word that meant "head or top."

It is possible that "cobweb" is related to that word, but a more
certain ancestor is the Middle English "coppe," which meant simply
"spider." Over the years "coppe" was gradually slurred to "cob," and,
voila, "cobweb.""

--SDSTAFF George, SDSTAFF Doug, and SDSTAFF Ken 
Straight Dope Science Advisory Board


Keyword search:

what are cob webs
cob web
cob webs not formed by dust
spider webs
cobwebs built by spiders


Best regards,
kitandgary-ga rated this answer:4 out of 5 stars
Fast and useful.  Thanks.

Subject: Re: Cobwebs: Spiders or Dust or ?
From: simon2wright-ga on 01 Jun 2005 14:43 PDT
Cobwebs are made by spiders, in time dust sticks to it and will appear
just to be made out of dust,
I dont think that dust can form a web without the help of a spider.

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