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FAMILY ARANEIDAE
- This page contains pictures and information about St Andrew's Cross Spiders that we
found in the Brisbane area, Queensland, Australia.
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 - Leg to leg female 50mm
-
- St Andrew's
Cross spiders are common in Brisbane bushes, backyard and gardens. They are easily recognized by the
bright pattern on their body and the cross stabilimentum
on their web. St Andrew's
Cross spiders build vertical orb web. In the middle they put four thickened zigzag
strips in the shape of a cross of 'X'. The spider then hangs head
down with its legs pairs together over the cross of
'X'. This is why they are called
St Andrew's cross spiders. Adult females build web about one meter in diameters and 1-2 meters above ground. The spiders
are active during day and night.
Female
- Female St Andrew's
Cross spiders are very different from the males. Adult females grow to 15mm in
body length. The abdomen is flat oval shaped with transverse white, yellow
and reddish-brown stripes. The thorax and head are brownish-silver under sun
light.
-
 -
- Legs are paired together, brown in colour with yellow bands.
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   -
- On the bottom side of the abdomen there are the yellow lines around the
black patterns, with the spinnerets in reddish brown colour.
Male
   - Leg to leg 15mm, adult male
Male approaching a female
Male and female
-
- Adult male St Andrew's Cross spiders
are much smaller than the adult female. They are dull brown in colour and with no
pattern on the abdomen. Both female and male St Andrew's Cross spiders have the hairy silver thorax and banded legs. All St Andrew's Cross spiders,
including male, young and matured female, rest with legs in pairs.
-
 - Male with only four
legs
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- We occasionally found male St Andrew's Cross spider with
some legs missing. The male in the above picture had only four legs. He
could had just mated with a female. In the spider's world, it is common that
the female may attack the male. Although this male was lucky enough to escape
after approaching a female, half of its limbs were broken.
-
- When the males approach the females, they always stay on
the opposite face of the web and slip between the threads for the purpose of
mating.
- St Andrew's Cross spider and some other spiders
make this zigzag band known as stabilimentum.
-
   -
- The function of those stabilimentum is uncertain yet.
Some believed that the zigzag is used as the sign to warn-off the larger
animals. Some believed that it is to stabilize the web. Some suggested that it
acts as a sunshade. Some suggested a molting platform and other suggested they
are depository of surplus silk. Recently found that those ribbon silk
reflect ultra violet light which is attractive to flying insects. This is a typical type
of question in Evolution, it may never have a single proven answer. However,
usually more than
a single answer, or
even most answers are correct.
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Egg-sac
  -
-
The
female lays her eggs in a silk sac which is close
to her web, then she extracts the liquid that dyes the egg-sac into dark
green colour.
-
-
- Female makes her egg-sac on late summer to early winter. Usually a female makes three or more egg-sacs.
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Juveniles
   -
- From late winter to early spring, the young St Andrew's Cross Spiders
hatch from the egg-sac. The young spiders stay together outside the egg
sac for a few days. Then they climb to the highest point and 'gone with the
wind' using the ballooning technique.
-
- Ballooning - A way that many species of spider used for travelling,
especially the young spiders. They hold a short length of silk which blowed by
the wind current. If the wind is strong enough, the young spiders travel with
the wind. By this way spiders can distribute in a very large distrance.
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Young Spiders
  - Leg to leg 15mm, young
female
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- Female St Andrew's Cross spiders are easily recognised by
theirs yellow bands on its flattened abdomen with reddish-brown and white dots.
The patterns may be a little different for different individual. The young
female spiders are smaller in size, with same abdomen pattern although the
colours are paler than the adult female.
-
 
 -
- From spring to mid summer, young spiders build web with
circular stabilimentum on lower plants. Their orb web is about 30cm in
diameter with circular stabilimentum, which make the web centre and the spider highly visible. They
are young St Andrew's Cross Spiders. They are pale brown to creamy white in
colour. As the spider grows the circular shape is gradually transformed into
cross shape.
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   -
Leg to leg 20mm, elder young female
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- Sometimes, the St Andrew's Cross
spider makes only one line. Sometimes, not very often, the spider
make two crosses.
   -
- A closer look at the silk spinnerets of St Andrew's Cross spider.
Sometimes the spider build really big cross. When disturbed, the spider will
either temporary drop to the ground (bungee jump with safety line) from the web
or shaking its web vigorously.
-
- Some orb web spiders, such as the Garden Orb Web
Spiders, only set up their web at night. The St Andrew's Cross spiders
set up their web 24 hours standby. However, they usually rebuild their web at
mid-night if necessary. In day time St Andrew's Cross spiders usually
repair (at minimum level) their webs if it was damaged.
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- We discussed about how spiders use their silk in this page.
On bird's diet menu
 - Photo thank to Trevor Jinks, Gold Coast
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- The bird is feeding a St Andrew's
Cross spider to its young.
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- Reference:
- 1. Wildlife
of Greater Brisbane - Queensland Museum 1995, p35.
- 2. St.
Andrews Cross - The
Find-a-spider Guide for Australian Spiders, University of Southern
Queensland, 2007.
- 3. A Guide to Australian Spiders - Densey Clyne, Melbourne, Nelson
1969, p67 (Argiope aetherea).
- 4. Saint Andrew's Cross Spider - Spider Fact sheets, Australian Museum, 2003.
- 5. Australian Spiders in colour - Ramon Mascord, Reed Books Pty
Ltd, 1970, p76 (Argiope aetherea).
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