SPIDER WEBS
G'day folks,
I love watching and taking photographs of spider webs. They are a bit like lightning. You never know what you will get. Here is some background on how and why.
A Typical Spider Web
An
orb-spinning spider puts its elegant traps together pretty quickly, proceeding
easily from step to step according to the instruction manual pre-programmed into
its brain.
Every web begins with a single thread, which
forms the basis of the rest of the structure. To establish this bridge, the spider
climbs to a suitable starting point (up a tree branch, for example) and
releases a length of thread into the wind.
With any luck, the free end of the thread will catch onto another branch. If
the spider feels that the thread has caught onto something, it cinches up the
silk and attaches the thread to the starting point.
It walks
across the thread, releasing a looser thread below the first one. It attaches
this thread on both ends and climbs to its center. The looser strand sags
downward, forming a V-shape. The spider lowers itself from this point, to form
a Y-shape. This forms the core support structure of the web.
The spider
easily grips the thin threads with special serrated claws, a smooth hook and a
series of barbed hairs on the end of its legs.
As it walks along the initial structural threads, it lays more frame threads between
various anchor points. Then it starts laying out radius threads from the
center of the web to the frames. The spider does not coat the frame and radius
threads with sticky material, since it needs to walk across them to get around
the web.
After building
all the radius threads, the spider lays more nonstick silk to form an auxiliary spiral,
extending from the center of the web to the outer edge of the web. The spider
then spirals in on the web, laying out sticky thread and using the auxiliary
spiral as a reference. The spider eats up the auxiliary spiral as it lays out
the sticky spiral, resulting in a web with non-sticky radius threads, for
getting around, and a sticky spiral for catching bugs.
The spider
sits in the middle of its web, monitoring the radius threads for vibrations. If
an insect gets caught in any part of the web, the spider will feel the motion
through the radius threads and make its way to the vibration source. In this
way, the web extends the spider's sensory system over a much wider area. The
spider might also leave the web, to retreat to a separate nest, while
monitoring the web via a connected signal
line.
Web-spinning
spiders have an innate ability to tell the difference between vibrations from
insect prey and vibrations from other sources (a leaf falling into the web, for
example).
Many species can also distinguish the characteristic vibrations of
dangerous insects, such as wasps, from their preferred prey.
When the orb web has deteriorated and is no longer
useful, many spider species will destroy it, eating up all the threads so it
can recycle the raw silk material. Spiders may leave the heavy bridge thread so
that they can easily rebuild the web at a later point.
Not all
spiders catch their prey by spinning a web.
Clancy's comment: Being a photographer has helped me to learn amazing things about nature, by viewing things much closer through the lense.
I'm ...