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Eriophora transmarina FAMILY
ARANEIDAE
- On the evening of later summer, in the bush along Bulimba Creek, we saw a
dragonfly fly into the orb web of the Garden Spider. We recorded how the spider
preyed on the dragonfly.
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 - Most Garden Orb Web Spiders build their web at night
and remove it before dawn. In
some cases, the spiders may leave their web as is during the daytime. On a
late summer evening when we were walking along the Bulimba Creek
and looking for insects, we notice a Garden Orb Web Spider just came out
from its retreat and started to build its web. Because the old web its built
on the day before was still there, we guessed it will remove the old web
first and then build the new web. When we were watching the spider start
actively checking its old web, suddenly we saw a dragonfly flied into its
web and got entangled. The dragonfly look like the female
Red Skimmer Dragonfly
(Diplacodes haematodes).
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 - At first the spider (on the far side of the camera, the blur brown
object) was a bit sceptical on this for it could sense that the prey on its
web was quite large. Spider
can feel the size of the object on the web by sensing the movement,
tension and vibration from the silks. The dragonfly was a skimmer and was
pale yellow in colour. Its wings looked very new too. From its colour and
wings conditions it could be a young adult just newly come out from its
pupa.
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 - The spider approach to its prey with high caution for it could be a
predator. The way that spiders handle prey on their web are different from
species to species, and its also depend on different prey. Some spiders will
bite their prey first and retreat, wait and see. If prey become motionless,
then they will warp their prey by silk. Some other spiders will pour silk
onto the prey first, until their prey is fully entangled, then they will
give them a bite. This will usually be the case if the prey is very large
and may fright back. I saw a Garden Orb Web Spider in our backyard, a Giant
Grasshopper fell into its web, when the spider approach, the grasshopper
kicked violently with its back legs. The spider just poured a large amount
of silk onto its back legs until they were entangled. Then the spider went
to the other side of the grasshopper and bite on its head.
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 - The spider approach to the dragonfly and find that there is not much
hitting back. Then the spider held the dragonfly and gave it a good bite,
until the dragonfly was motionless. Notices that the spider had prepared a
large bundle of silk, which could be useful in case the dragonfly fright
back.
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 - After a few minutes, the spider found that the dragonfly was unconscious,
the spider warp around the dragonfly by silk and make sure it is well
connected to the web, then the spider check around its web to find out if
the web was not damaged too badly. Usually, if the web is build for that
night, the spider will repair it a little bit and than start to feed on its
prey. For this spider, it just continues to remove the old web and start a
new web again.
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- Spiders do not swallow nor chew solid foods. Spiders digest their food
externally. They secrete their saliva that contains enzymes which can
decompose the prey body. Once their food is liquefied, the liquid is sucked
into the stomach. Food is then store in the midgut.
For more information about spiders digest system, click here.
We also recorded how
they build their webs.
Questions for Discussion
- There is a simple experiment that we can show the spiders can sense the
size of prey on theirs web. Next time when you see a spider web with a
spider sitting at the middle, try to find a thin, real thin, and long grass.
Uses the tip of the grass to disturb the web. If the grass is really thin,
the spider will think there is a small prey fall onto the web and the spider
will rush to the point you disturbed and try to bite your grass and pour
silk on it.
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- If you use a long stick or thick grass with the considerable mass, the
reaction of the spider will be different. No matter how slightly you disturb
the web by a stick, you body weight to transmit through the stick to the
spider and its know a big thing is coming. It will run away back to its
retreat, drop to the ground or run to the top of the web, whichever is
easier for the spider.
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- Remember, when you do the about experiment, use a long enough grass or
stick and make sure the spider cannot bite you at your figure. I am quite
sure the spider will not run to your hand along the stick. Please also
remember you are just joking with the spider, do not damage its web too
much. For the spider have to spend hours to build it.
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