Argiope aemula (Walckenaer) 1841
Oval St. Andrew’s Cross Spider


Family : Araneidae, Orb-Web Spiders.
Habitat: Low shrubs beside hiking trails at the fringe of primary and secondary forests.
Female: 25-30 mm. Male: 5-8 mm.
Distribution: Singapore, Malaysia, Indonesia, Thailand , the Philippines, Brunei (new record), Papua New Guinea, Vietnam, Sri Lanka, India, Taiwan, China, Southern Japan, Northern Australia.

A lone male Oval St. Andrew’s Cross Spider by a lake in Sabah.


A female Argiope aemula (Oval St. Andrew’s Cross Spider)

This is a female Argiope aemula (Oval St. Andrew’s Cross Spider)

Unlike many other Argiope spiders, the abdomen of an Argiope aemulais is oval.

 

A female Argiope aemula (Oval St. Andrew’s Cross Spider)

Argiope aemula spiders webs are vertically 1-2 meters above ground.

The web of mature female spiders can be easily recognized by the X-shaped zigzag bands of white silk in the centre of the web.

 

Photo Left : A female Oval St. Andrew’s Cross Spider.

The brilliantly colored spider with silvery hair on the carapace sits head down in the centre of the web, and holds its legs in pairs in such a way that they appear to be aligned to the four arms of the letter 'X'.

 

A male Argiope aemula (Oval St. Andrew’s Cross Spider)

Photo Left : A male Oval St. Andrew’s Cross Spider.

The males are dull in color and like the females, have the habit of pairing their legs.

The male's webs are, however, decorated by a lace-like centre, instead of white bands in the shape of the letter 'X' in the female's.

 

More about Male Argiope aemula spider of Malaysia
 

Photo below : A lone male Oval St. Andrew’s Cross Spider by a lake in Sabah.


The Spinnerets - Spinners of a spider - Silk spinning organ of the female spiders

In this silk spinning organ, most spider species has just one pair of spinners. Some has as many as four pairs.

Each spinner has it own function.

There are small tubes in each spinners. All tubes are connected to the glands.

The number of tubes varies in each spider species between 2 and 50,000.

A spinneret is a spider's silk-spinning organ. It is usually on the underside of a spider's abdomen, to the rear. Most spiders have six spinnerets; some have four or two. They move independently and in concert to build webs.

Cribellum - additional silk spinning organ in some spider spicies.

Some spiders have an additional silk spinning organ called a cribellum situated in front of the normal spinnerets and consists of  one to four plates covered in spigots


Silk Gland Name Spinnerets Used Type of Silk
Piriform Anterior Disk Attachment
Ampullate Anterior/Median Dragline and Web Frame
Aciniform Median/Posterior Wrapping silk, Sperm-web, Egg-cocoon (outer wall)
Tubuliform Median/Posterior Egg-cocoon
Aggregate Posterior Spiral parts of Sticky-web
Flagelliform Posterior Axial thread of Sticky-web

This female Orb-Web Spider of Malaysia did not spin silk all over the pray (an owlfly), it merely spray silk to the 3 major moving parts - first the wings, then the abdomen follow by the head. The whole silk spinning process took only couple of seconds. After which the spider return to her original position and wait as if nothing had happen.

Minutes later, the spider return to its pray and began sucking body fluid from the owlfly.



The silk spinning organ of a female Argiope aemula (Orb-Web Spider) has 5 spinnerets (spinners).

When in resting position the spinning organ is in a circular position with the end tip of the 5 spinners meet in the center.

But when the organ is in action to spin silk on the pray, the spinnerets (not all) expended and erected and the many tinny tubes on each spinnerets ejected a fine tinny liquid form of silk hitting the pray. The watery silk harden almost within split second and wrap up the pray.



長圓金蛛

Argiope aemula (Walckenaer) 1841

Oval St. Andrew’s Cross Spider

Family :  Araneidae, Orb-Web Spiders.
Habitat: Low shrubs beside hiking trails at the fringe of primary and secondary forests.
Female: 25-30 mm.      Male: 5-8 mm.
Distribution: Singapore, Malaysia, Indonesia, Thailand , the Philippines, Brunei (new record), Papua New Guinea, Vietnam, Sri Lanka, India, Taiwan, China, Southern Japan, Northern Australia.

 

A very common garden spider in Malaysia, conspicuous because of its large size (body an inch long) and its tendency to construct webs in open places easy to see.

This Garden Spider known as the Black-and-yellow Argiope. This big spider wrap pray such as grasshopper in a mummy-like cocoon of silk, then bite through the cocoon and begin sucking out the juices. One special feature about this species' web is that in the center there's a bright, vertical stripe of zigzagging silk.

Argiopes hang head-down in their web's center.

 



This species prefers sunny areas among flowers, shrubs, and tall plants.


Like many other spiders, the male is half to one-third the size of the females.

Like many other spiders, only the female Argiope mangal build the webs. These are orbs 38-50mm wide and contain only 2 stabilimentum. Argiope versicolor, which is found inland, makes the "full" cross with 4 stabilimentum. When prey is caught in the web, the spider throws out broad swathes of white silk to immobilise the prey, then rapidly rotates it to tighten the binding before administering the fatal bite. Small spiders which are unable to rotate the prey, run around the prey instead as they throw out binding silk.

When it is disturbed, Argiope mangal vibrates the web so its outline becomes blurred. Another response to flip to the other side of the web in a blink of the eye, through a gap in the web. Yet another response is to simply drop off the web. Large ones may simple wiggle their abdomens, which have a pair of large black eye-like dots.
A rare look at
a moulting spider

Role in the habitat: like other predators, the spiders keep the population of their prey in check. They in turn, are eaten by other creatures in the food chain.

Genus Argiope


This very well known spider is also known under the name 'garden spider'.
There are 25 known species in this genus but the most beautiful and spotted one is the Argiope Keyserlingi ( formerly aethera) or 'St Andrew's cross spider'

The spiders of this family are easily identified by the zig zag silk construction (stabilimentum), usually a cross, they make in their web.
It is believed that the spider uses it to camouflage itself in the cross and to warn birds not to fly through the web.
But there are also other hypotheses.
Perhaps the most important function of stabilimenta is to attract insects. The silk of the stabilimentum reflects UV light and pollinating insects are lured to these threads.
If the spider is attacked it starts shaking vigorously in her web. The whole web becomes white because of the stabilimentum. This frightens of attackers.
The web is usually constructed a few decimeters above the ground in tall grass and among shrubs.

 

Spiderling is difficult to identify. But the eyes arrangement in 2 rows (above the photo) of this spiderling confirm that this new born is similar to the species Argiope aemula (image inserted).

Hatchlings generally resemble small adults, there are no major changes in anatomy or structure as they grow except the development of reproductive organs.

 


Argiopes spiders produce large numbers of young in their egg sacs.

Female produce one egg sac triangle in shape. The color of the egg case is yellowish white.

Unlike some spiders, such as the green lynx who guard their eggs and young, Argiopes leave their eggs to their fate.

The mother carefully anchored within a framework of silk strands, keeping it away from surrounding vegetation. This protects the case from predators like ants.

The young spiders hatch within 3 weeks in tropical weather of Malaysia.

These cases are very well constructed and last through months after spiderling emerged, before the weather eventually takes its toll and the cases are washed to the ground.


20-8-2009  6:54 am  Thursday

Before was a clean and neat egg case (see the same egg case above taken days before), when the spiderling emerge, each spiderling added extra lines of fine silks around the egg cocoon.

These fine, white, non sticky silk from the baby spiders added extra protective layers to the spiders still inside the egg case.

Ants, which like to hunt on baby spiders, are difficult to pass through these massive maze of spider web build by the newly emerged spiderling.

 


20-8-2009 7:12 am Thursday

Two full weeks passed.........

On the morning of 20 August 2009, finally I saw emerged spiderling around the egg case. (Above of photo). The spiderling might had fully hatched few days earlier but remain dormant inside the egg cocoon waiting for a right moment at a right weather.

The previous day (yesterday) was a hot sunny day, a good day for these spiderling to emerge from the egg cocoon.

Spiderling congregated below the egg case (Below of photo) but few inches above the ground. Here slight above the ground they formed a community web using each of their own silks.

 


5-8-2009  7:11 am  Wednesday

5-8-2009  7:12 am  Wednesday

4-8-2009  7:18 am  Tuesday

 


Stabilimentum


Besides their standard orb-web, Argiope spiders build additional white opaque zig zag lines on their webs, called stabilimentum.
The shape of the stabilimentum changes with the age of the spider. First it starts with a circular white web in the center. Later it changes to a cross and when the spider is full-grown only a small zig-zag remains
Sometimes the zig-zag lines match their leg positions, which lead some people to suggest that this helps give the appearance of longer legs. Some spiders build a single vertical line, yet others a patch of zig zags in the centre of the web. No matter the design, the spider sits right smack in the middle.

Stabilimentum stabilize the web (hence their name!) . Stabilimentum warn larger animals in the same way that safety strips on glass doors warn people from walking into them. Thus the web is protected from damage by flying birds.
Research has shown that the silk in the stabilimentum reflects ultraviolet well, unlike the silk used in the rest of the web.
Stabilimentum designs may mimic flowers, which also reflect ultraviolet light well, and often have lines to guide insects to honey like airport lights do for airplanes. Instead, the insects are guided to the spider which sits in the centre!!



Argiope aemula (Walckenaer) 1841

Oval St. Andrew’s Cross Spider

Family :  Araneidae, Orb-Web Spiders.
Habitat: Low shrubs beside hiking trails at the fringe of primary and secondary forests.
Female: 25-30 mm.      Male: 5-8 mm.
Distribution: Singapore, Malaysia, Indonesia, Thailand , the Philippines, Brunei (new record), Papua New Guinea, Vietnam, Sri Lanka, India, Taiwan, China, Southern Japan, Northern Australia.


The Spinnerets - Spinners of a spider - Silk spinning organ of the female spiders

In this silk spinning organ, most spider species has just one pair of spinners. Some has as many as four pairs.

Each spinner has it own function.

There are small tubes in each spinners. All tubes are connected to the glands.

The number of tubes varies in each spider species between 2 and 50,000.

A spinneret is a spider's silk-spinning organ. It is usually on the underside of a spider's abdomen, to the rear. Most spiders have six spinnerets; some have four or two. They move independently and in concert to build webs.

Cribellum - additional silk spinning organ in some spider spicies.

Some spiders have an additional silk spinning organ called a cribellum situated in front of the normal spinnerets and consists of  one to four plates covered in spigots


Silk Gland Name Spinnerets Used Type of Silk
Piriform Anterior Disk Attachment
Ampullate Anterior/Median Dragline and Web Frame
Aciniform Median/Posterior Wrapping silk, Sperm-web, Egg-cocoon (outer wall)
Tubuliform Median/Posterior Egg-cocoon
Aggregate Posterior Spiral parts of Sticky-web
Flagelliform Posterior Axial thread of Sticky-web
 

Spiders of Sabah  November 10, 2014 08:18:37 AM

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