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Spiders - Introduction & General Information
As with other animal types, spider diversity in
the Wet Tropics is broad and many fascinating species occur here
that range from the ominously large to the tiny and hardly noticed,
and from the dullest browns or black to the vibrantly hued or deceptively
shaped.
Spiders can be roughly classified according the strategies
they use for feeding. Spiders which appeared earlier in the evolutionary
scale feed by waiting in a burrow for food to come along before
grabbing it. Following them were spiders which actively wandered looking
for food and which caught it by ambush or chasing it down. The evolution
of flying insects generated an incentive for spiders to evolve new ways
of catching food which couldn't be chased and so the earliest aerial web
weavers arose.
A few facts about spiders:
- Most spiders feed on insects and other arthropods
but the Whistling Spider or Tarantula (known as the Bird-eating Spider - see the Primitive
spiders page) has been documented taking and feeding on frogs and small birds. The Golden Orb Spider also regularly traps small birds in its strong web and usually kills them.
- Spiders cannot eat solid food - they suck out
their victim's body fluids and softer tissues using powerful stomach
muscles.
- A spider periodically sheds its skin (exoskeleton)
so that it can grow (called moulting). Immature stages in between
moults are called moults.
Each species has a particular number of moults that it will go
through before reaching its final adult stage.
- The silk used to create webs or
wrap up caught prey is made mostly of proteins and amino acids.
There are at least seven different types of spider silk created
for specific uses (such as web construction, anchor lines, wrapping
prey and lining nests) and most spiders possess at least three
types of spinnerets. These extensions at the end of their abdomen
exude a liquid under pressure which becomes the threads, some of which may be very sticky.
- Usually, once male spiders have mated, they no
longer have any interest in eating and die shortly after. But,
even in death, Redback males often serve a purpose. The already engorged and gravid Redback females always kill their suitors and, in most cases, also eat them. This provides them with a small reproductive advantage.
Allowing spiders to take up residence around dwellings
can be beneficial in that they catch other annoying insects such
as mosquitos and flies. If you find a spider in your home that you
don't want there, you can use a large drinking glass to trap it
by gently placing the open glass over the spider as it sits on a
wall or flat surface; slide a sheet of paper under the rim so that
the spider is trapped inside when you move the glass. Take it outside
and toss it into a shrub or let it escape onto a tree trunk. Avoid
using insecticides to kill spiders as these chemicals also kill
other animals like frogs.
Rest assured that while you might see some large
spiders, and perhaps even some venomous ones, none will behave like
the Australian spider, Delena cancerides, wrongly portrayed as a dangerous villain in the horror film Arachnophobia! A good
'rule of thumb' regardless is to look and admire but don't touch
any spider you find. Even those without venom could still have a
nasty bite.
After you've had a read through our spider profiles
pages, you can visit some of the museum web sites around Australia.
Here are a few handy links:
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