Biology, behavior, and ecological roles of SPIDERS found in EAST MALAYSIA (BORNEO)

SPIDERS OF BORNEO > Biology, behavior, and ecological roles of SPIDERS found in EAST MALAYSIA (BORNEO)

The number of spiders (families, genera and species) recorded from South East Asia.

	Families	Genera	Species
Indonesia	50	249	660
Borneo Island (Sabah, Sarawak, Brunei, Kalimantan)	42	181	463
Myanmar	43	175	455
The Philippines	39	189	426
Singapore Island	39	186	308
Thailand	35	82	156
Vietnam	30	134	230

If spiders have a less than desirable reputation, they have only themselves to blame. They do not possess the beauty of butterflies. They do not go about their business in an open and defenceless manner, as ants do. And they often find themselves unwelcome houseguests, spinning webs wherever they please, much to the disapproval of their put-upon hosts.

Although most educated people today know that spiders do not cause illness, few tolerate spiders living in their homes.
Spiders are the innocent victims of a negative image. Most domestic spiders are harmless to humans. The Heteropodidae species that we often come across at home are actually well behaved for the most part.

The nocturnal Heteropodidae spiders do not disturb people during the day and do not produce any webs. Unlike other spider species that eat their young, the female Heteropodidae spider protects her eggs and cares for the larvae. They even help keep away other unwelcomed houseguests, as they are skilful at capturing and devouring cockroaches. The best way to get rid of this species of spiders in the home is not to kill them at every opportunity, rather, all you need is a cockroach-free environment.

The total number of spider species discovered so far on BORNEO ISLAND stands at around 500. Hundreds of species are still waiting to be discovered.

spiders with vivid colouring tend to draw the attention of their prospective prey more successfully than those with less vivid colouring.

The odds of his being bitten by spiders, venomous or not, are slim. Spiders aren't an aggressive type of predator. In most cases when they feel threatened, they try to flee or play dead by falling from their webs and then quickly run for cover.
The reaction to a bite from a poisonous spider, varies from person to person, depending on one's physical constitution. For example, the venom of the Latrodectus mactans, or Black Widows, can be fatal particularly for children.

Sparing especially rare species of spiders to allow them to live and multiply freely in the wild. The fierce competition for survival already puts a limit on the population of spiders. In many cases, baby spiders can even fall prey to their mothers when they accidentally intrude upon their mothers' webs.

As a result of such dangers, most spiders tend to be loners and do not travel far because of their limited ability to move to other regions. Smaller spiders, on the other hand, often make good use of their natural endowments--the spinnerets, the silk glands, and the spigots--to reach more remote areas. The spigots allow them to extract silk threads from the silk glands inside the several spinnerets, and the smallness and lightness of their bodies enable them to be taken by the threads and thus "balloon" with the wind. They can go as far as the wind takes them with these threads.

Spiders have many different silk glands, and each has various functions. Spinning spiders generally have three or four kinds of silk threads. Some of these threads are used to create webs, a thicker drag line is used to support the spiders when they fall, an adhesive type traps their prey, and several other kinds that vary in softness and thickness are used to wrap their eggs.

They're fascinatingly designed. Even a spider of less than one millimeter in size is likewise intricately built. And to add to the variety, different species of spiders produce webs of different shapes. For instance, the Nephila pilipes spiders spin their webs in the shape of a hoof, the Argiope aetheroides species weave a white X shape in their round webs, and the Octonoba spinosa spiders braid spiral-shaped webs.
Spiders are environmentalists because they usually "recycle" their webs by eating the protein-enriched threads when they prepare to move on. Another interesting aspect of spiders is the size discrepancy between males and females. Females are generally much larger so they can carry as many eggs as possible. Males, meanwhile, are rather small since their only function is to mate, and they often die soon after they perform this duty.

Certain species of female spiders die soon after laying their eggs. But before doing so, they wrap their eggs neatly and hang the egg sacs on trees. The newly hatched baby spiders are forced to start their lives on their own, and many of them either die from hunger or are quickly killed. On the other hand, those species that raise their young tend to produce fewer descendants. In general, most spiders have a life span of one to two years, during which period they molt six or seven times.

Hundreds of species of spiders are hiding in the high mountains of BORNEO waiting to be discovered, named, and added to the list of identified species.
With keen eyesight and years of arachnid study, a biologist can easily detect a spider the size of a grain of sand from its surroundings. But most often fails to find enough time to go through the volumes of documents to determine whether or not he has encountered a new species.

Scientists are needed to continues to pursue research in classifying and studying the huge variety of spiders species found in Borneo Island, with a particular focus on interesting aspects such as spider genitalia.

Different spiders adopt highly disparate strategies to seek out prey animals and have developed morphological and behavioral traits that complement their hunting methods.

All spiders are carnivorous, feeding on prey such as insects, other invertebrates, small vertebrates and even other spiders.
To immobilize prey, spiders inject venom from a pair of fangs. The venom is a neurotoxin that causes paralysis, allowing the spider to ‘vomit’ out digestive enzymes that cause the prey’s innards to liquefy. The spider then sucks up the fluid, leaving behind a dry husk. No Asian species is known to have venom that is fatal to man, although some have painful bites.

Spiders are classified under the taxonomic order Araneida in the class Arachnida which also houses scorpions, mites, ticks, whip scorpions and just about any anthropoid you might come across that does not have six legs. There are at least 30,000 named spiders (and thousands more still undecided).

Above image : The pray is an owl fly Ascalaphidae
Body fluid from the pray being sucked up. Just lest then minute ago the pray was trapped in the web. The spider immediately spray several layer of silk on the owl fly follow by an inject of venom from a pair of fangs. The venom is a neurotoxin that causes paralysis. To consume the paralyzed pray the spider ‘vomit’ out digestive enzymes that cause the prey’s innards to liquefy. The spider then sucks up the fluid, leaving behind a dry husk of an owl fly.

The female Argiope aemula spider is about 20 mm in body length.

A fang is a long, pointed tooth. In mammals, a fang is a canine tooth, used for biting and tearing flesh. In snakes, it is a poison-injecting tooth (see snake venom).

Spiders have a pair of fangs, which are part of the chelicerae.

The Cheliceral fang of a spider is so called because the chelicerae of spiders consist of two parts, one containing all or part of the glands that produce the spider's venom and the other part a kind of organic hypodermic needle through which the venom is injected into prey animals or other animals that the spider bites, e.g., in self defense. The term "fang" ordinarily describes the two long prominent teeth of canines that are used to produce deep wounds, but the fangs of spiders are structurally more like the fangs of venomous snakes since their teeth are hollow and are used to inject poison. Spider fangs, however structurally similar, evolved some 400 million years ago (while snakes are some 150 million years old) and they are not made of calcium. Instead, they are composed of chitin, which is a kind of protein. The fangs grow again whenever the spider molts which is a great advantage in case the spider had lost or broken one of them; however, as chitin needs a few days to become hard, the spider is vulnerable before the fangs are fully useful again.

Web builders are typically sedentary creatures with a fixed territory. They have relatively poor eyesight, relying primarily on tactile senses for navigation and prey detection. They “taste by touch”, using their sensitive legs to detect movement and vibrations on their web that indicate the presence of entangled prey.

1- Spiral Orb Webs
2- Tangle Webs or Cobwebs
3- Sheet Webs
4- Funnel Webs
5- Triangle Webs

Web spinners

Different web spinners have their own approaches to handling prey. Some wrap the struggling animal in a cocoon of silk (using their fourth leg to skillfully twirl the thread ejected from their spinnerets at their abdomen around the prey like a live mummy) before delivering the immobilizing venom. Others bite first and do the wrapping work only when the pray struggler. A number of species like their meal well crushed before partaking of the resulting amorphous lump of organic matter. Others like their entrées whole, leaving behind clean shells of once buzzing insects.

Wrapping a pray
Some wrap the struggling inset in a cocoon of silk (using their fourth leg to skillfully twirl the thread ejected from their spinnerets at their abdomen around the prey like a live mummy) before delivering the immobilizing venom.

Paralyzing Bite
Others give an immobilizing venom bite first and do the wrapping work only when the pray struggler.

Crushed Meal
A number of species like their meal well crushed before partaking of the resulting amorphous lump of organic matter.

Araneidae Family

Vertical orb web
In Araneidae are the so-called spiny spiders (genus Gasteracantha) which build vertical orb webs. The spiders, which have spiky extensions that can be longer than the body itself, sit boldly at the hub of their webs during the day, as they are unpleasant tasting, with appropriately gaudy warning colorations.

Tetragnathidae Family

Horizontal orb web
Horizontally suspended webs are built by spiders in the genus Tetragnatha, which are known as ‘big-jaw’ spiders.

Uloboridae Family

Hackled orbweaver webs

The hackled orbweavers (family Uloboridae) have the special distinction of being non-venomous spiders. Their lack of poison glands is a secondary evolved trait.

All members of this family produce a feathery, fuzzy silk called cribellate (or hackled) silk.. These spiders do not use an adhesive on their orb webs, but rather the very fine fibers on each strand of silk tend to ensnare prey. Hackled orbweaver webs often have a stabilimentum or zig-zag pattern through the center.

Web architecture is part a spider’s extended phenotype. The classic orb web is spun by members of the families Araneidae, Tetragnathidae and Uloboridae.

Orb webs are both beautiful and complex structures.

Essentially, Orb Web is made up of an anchored frame, with radial lines that connect the frame to the centre of the orb. Most of the web is made from different types of non-sticky silk from the spinnerets. Only the prey-snaring capture threads that form concentric spirals around the hub are made from sticky silk.

Free zone (a gap between the spiral threads)
Some orbs have a free zone (a gap between the spiral threads) in the hub that allows the spider to easily move from one side of the web to another.

Horizontally webs
Horizontally suspended webs are built by spiders in the genus Tetragnatha, which are known as ‘big-jaw’ spiders.

A number of spiders, rather than sitting squarely on the hub, hide nearby and use a signal line attached to the web that vibrates when a prey hits home. A further variation are webs with hubs that are built around a leaf. One unusual vertical orb web spinner is Poltys illepidus, the so-called tree-stump spider for its uncanny resemblance to the broken end of the stick. It assumes this camouflage position in the day, building a new web every night and consuming it at daybreak to reingest the valuable proteins.

Even casual observers in local parks and reserves would find it hard to notice the large orb web spiders Nephila maculata and Nephila pilipes on their huge, yellowish webs that can be a couple of meters wide. To protect the main web from unsuitable catches or bumbling ducks monkeys, barrier webs are spun nearby. The spiders sit on the hub facing downwards and the vertical web is fittingly asymmetrical, with the lower portion covering a much greater area than the upper. Despite their size and ferocity, Nephilas can fall prey to a species of wasp that lays its egg on the spider's back. When the larva hatches, it feeds off the living spider and as a penultimate gesture, causes the spider to spin a final web that has no prey-catching ability but is strongly secured, after which the larva dishes out the coup de grace (by literally sucking the life out of the spider) and pupates in the safety of the web.

Daytime shelter

Some spiders knows how to improve life by building living facilities.
Pond Wolf Spider Pardosa pseudoannulata is one of the most conspicuous wolf spiders. This female spider form webbing only to provide daytime shelter from the hot tropical sun, not to capture prey.
The exoskeleton of spiders doesn't grow with them, so all spiders have to molt (shed their skin) to grow. They only molt when young, and cease to molt once become an adult.
This female wolf spider is 7mm in body length.

Camouflage traps

Webs are also ‘decorated’ by some spiders, which place debris to camouflage the traps, or decoys such as egg sacs that mimic the spider’s appearance as a strategy against predatory wasps.
This spider length is about 3mm

Photo above : An moldy and empty dead body case of an unidentitified spider spices found in Bukit Gemok, Malaysia. Note the absent of the spider abdomen believed to be consumed by larva of certain wasp species that lays its egg on the spider's back.

Some big spiders easily fall prey to a species of wasp that lays its egg on spiders. When the larva hatches, it feeds off the living spider and as a penultimate gesture, causes the spider to spin a final web that has no prey-catching ability but is strongly secured, after which the larva dishes out the coup de grace (by literally sucking the life out of the spider) and pupates in the safety of the web.

Stabilimentum (lace-liker zigzag bands)

Orb webs with stabilimentum (lace-liker zigzag bands) are built by Argiope spiders, which align their legs to the stabilimentum, which may be 4-armed or 2-armed. Stabilimentum in the form of a lacy network can also be found in the hubs of some webs. They also serve as sunshades for some spiders.

Dome Web

Photo above : A dome web of a Psechrus sp BORNEO spider. One of the largest (30-40mm) spiders in Malaysia.
The dome web is about 0.5 meter in diameter supported with 1 meter length of many hanging vertical silk above.
The tube retreat is in the tree trunk at left.
The Dome web was build under the projected fern leave (see photo) This leave served not only as support to the web but also serves as a shad.
Since the fern leave is soft and swing with every breeze, in order to stabilize the leave (and the dome) a bunch of about 50 thicker and harder vertical silks were constructed to hold the fern leave to another tighten leave above. (see photo). A very brainy architecture engineering from a small creature.

English Reference :

An Introduction to the Spiders of South-East Asia
by Frances Murphy (Author), John Murphy (Author)
Publisher ‏ : ‎ Malaysian Nature Society; First Edition (January 1, 2000)

Common Spiders of Borneo