“You guys have
started to pick up some interesting topics lately”, commented Shikhar in our college
whatsapp group in response to our last blog post on how lizards manage to cling
and move on walls. While the post, due to obvious reason of being about
lizards, made few of our readers go ‘eww’, Shikhar and few others found it
really enlightening. While we were thanking Shikhar for his kind words, he
asked a question. “Is the spider’s web really as strong as they show in the
spiderman movies?”. Well, I told him, that I will find that out for you. And
here I am, fulfilling my promise.
Spider webs
are a common sight around us. Small webs made by spiders near the corners of walls
and ceilings. These webs are multipurpose device created by spiders sometimes
to protect their bodies and eggs, but primarily to catch their prey. However,
there are few species of spiders who do not built webs at all or catch prey
using other methods as well.
Spiders (along
with few other insects and larva) are gifted by nature with a special organ
called spinneret, which is a silk
spinning organ. Spiders spin silk using these organs. Silk spun is a protein fiber
that spider uses to build the web in various shapes.
 |
| Spider hanging from web |
The most
common type of the web that we see is the Orb
web, which is built in a vertical plane. We all must have appreciated the
perfection and symmetry of an orb web whenever we saw one. Interestingly,
spider uses its own body for measurements while building the orb. An average
spider takes close to 60 minutes to build a full-sized orb web, which can be up
to 20 times the size of spider itself.
 |
| An orb web |
Once the
spider has completed building the web, it sits on or near the web and waits for
the prey to get trapped. Once the prey hits the web, and struggles to free
itself from the sticky web, the spider senses the vibrations in the web
structure and gets to know that dinner is ready.
Why so spiders do not get trapped in their own
web?
Spiders can
weave both sticky and non-sticky threads of silk. While making the web, the
spider uses both sticky and non-sticky silk and later carefully uses the non-sticky
ones to traverse through the web. In addition, they also have dense hair and
non-sticky coatings on their feet to prevent them from sticking to a sticky
thread if they mistakenly step upon one.
But the question is still unanswered, is the
web really that strong?
Well, the
short answer is ‘yes’. But the short
answer doesn’t quench the thirst for knowing more, so we have a long answer
too. Spider silk has a strength comparable to that of steel. If you have a
steel wire with same thickness as spider web, depending on the type of steel,
the steel wire may be stronger. However, if you take same weight, the silk will
beat steel hands down. Reason is that the silk has a lower density compared to
steel, and a wire of steel will be much thinner than thread of spider silk, of
same weight. However, spider silk is not as strong as Kevlar, a synthetic fiber.
However, if
we compare toughness, spider silk is tougher than both steel and Kevlar.
Nerd note
1: Spinnerets are located at rear end of the spider’s abdomen. Now you know why
Spiderman hangs upside down.
Nerd Note 2:
Tensile strength of a fiber is the resistance to change its shape. Toughness is
the amount of energy required to crack it.
Many thanks
to Shikhar for suggesting this topic and giving us an opportunity to know more
and share more.
And as
always, thanks for
reading.
Ayush!!!
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