Welcome to the World of Spiders!
Spiders are some of the most amazing creatures of the world, thanks to their unique body structure and behaviour which distinguish them from all other forms of creatures: You will know a spider when you see one. However, astonishing as they may be, spiders are not exactly the most popular to humans. Unable to accept their hairy and eight-legged nature, most people tend to avoid, flee or even kill spiders with each encounter; and the constant portraying of giant spiders as villains in movies doesn’t help either. Arachnophobia, or the fear of spiders, is mainly caused by the lack of understanding.
Here at Wildlife Malaysia, we believe that knowledge is the key to understanding and appreciation, even towards creepy crawlies like the spiders. So now, just how much do you know about your spiders?
Anatomy (Body Structure)
There are a wide range of spiders out there: some huge, some microscopic, some look like ants, others like scorpions etc. How do you tell a spider apart from other insects or creatures?
Well, it is actually pretty simple, all spiders:
1. Have 8 legs, though sometimes one or more legs could be missing due to injury.
3. Have chelicerae and fangs, 99% of all spiders are carnivores. The orientation of the fangs may be different depending on the type of spiders.
5. Have 6-8 eyes. 99% of today’s spiders have 8 eyes.
2. Produce silk, though not all spiders use the silk to build webs.
4. Have a body divided into two segments– cephalothorax (prosoma) and abdomen (opisthosoma).
Most of the time, you can easily identify a spider based on the points above, though you might need magnifying glasses for tinier subjects.
Apart from a few group of spiders that hunt actively like the Jumping Spiders (Salticidae), Huntsman Spiders (Sparassidae) and Net-Casting Spiders (Deinopidae) etc., most spiders do not have great eyesight despite having 6-8 eyes! So how do they eat you ask?
Most spiders rely on force and vibration to sense, and eventually catch their prey (with the help of a web, of course!). A prey stuck on a spider web will not attract the spider’s attention so long as it doesn’t struggle.
Spiders are able to detect vibration, sense and even smells using fine bristles located throughout their legs.
Spiders may range from microscopic at 0.43mm (male Patu marplesi) to frighteningly enormous at 30cm leg span (Heteropoda maxima).
There are hundreds and thousands of flora and fauna all over the globe, and it will be ineffective, if not total chaos to understand, learn or research on them without a proper, scientific grouping system. This was why a Biological Classification of 8 taxonomic ranks, a scientific method to group organisms hierarchically was introduced. Without this system, we would not have been able to differentiate an insect from a spider, let alone all the scientific progress we have achieved thus far!
Spiders are arthropods- invertebrates (i.e. no backbone) with segmented bodies (i.e. division into cephalothorax and abdomen) and jointed appendages (i.e. segmented legs and palps).
Spiders are grouped under the Class Arachnida (hence the common term “Arachnids”) along with closely related arthropods such as mites, scorpions, harvestmen, whip scorpions etc.
Like humans, spiders occur in male and female sexes. Spiders are sexually dimorphic- male and female spiders look different from one another (just like a man being different from a woman in terms of appearance). In most cases, it is fairly easy to differentiate adult male and female spiders by looking at their reproductive structures.
Adult males usually display swollen palps (or pedipalps) which store sperm required to fertilize the female spider.
Adult female spiders are generally larger than males, where some can be up to 20-30 times larger! All adult females possess a reproductive structure on the underside of the abdomen called the epignye which accepts the sperm from the males.
Spiders are shielded by exoskeletons made out of chitin and proteins. The rigid and fixed armour provides the much needed protection for spiders but restricts growth, which is why spiders, like other insects, moult (in a process called ecdysis) in order to grow. It is also hypothesized that the onset of moulting is also caused by other metamorphosical factors.
In preparation for ecdysis, most spiders will lose their appetite and activeness, as the body releases enzymes that softens the existing skin to soon be shed. It is said that spiders undergoing moulting are not capable of breathing.
The “new” emerging body is initially soft and fragile, and will slowly harden with time. During this time, the spider is especially vulnerable to harm. The spider will not be able to feed as well until the new fangs harden.
Spiders shed their skin approximately 5-10 times during their lifetime (larger and longer living spiders may moult more) and it is known that the shape (morphology), anatomy, colours and even behaviour will change with each moult.
Reproduction and Life Cycle
Spiders reproduce sexually through internal fertilization within the female. However, the mating process is rather “indirect”: After determining the suitability of the female spider, the male will release his sperms onto tiny, specialized webs before being “loaded” into his specialized pedipalps. The mating process involves the male getting to the underside of the female spider, and releasing his sperm into the female reproductive structure (epignye).
In reality however, the mating process is not that straightforward, mainly because of the relatively large sizes of female spiders. The males have to tread carefully so as to not be mistaken as food! In many instances, the males have to perform courtship rituals in order to entice or excite the female prior to mate, which include coordinated vibration of the female’s cobweb, erotic rubbing of body parts or even graceful mating dances.
A pregnant (or more correctly gravid) spider will then deposit hundreds of eggs on specialized egg sacs from which spiderlings will emerged from after a few weeks. Most mother spiders will stick around and care for their young, though the intensity of care varies from one spider to another.
In general, spiderlings will stay together on their mother’s sanctuary until their first or second moulting before heading out to see the world. These juvenile spiders will have to undergo a few more ecdysis before they become mature and capable of mating.
Perhaps one of the main reasons why people are afraid of spiders is because of their abundance. Spiders are terrestrial and can be found throughout the world except for Antartica. Different types of spiders have evolved different tricks and mechanisms to allow them to thrive in specific environments. Some spiders excel at living underground, some on trees and shrubs, some near or even in freshwater!
So how do something as small as spiders travel and colonize such vast ranges of habitats? Well, they certainly don’t do much of the travelling by foot! Most web spiders are capable of releasing their silk into the air and count on the wind to bring them to new places. YES, spiders can “fly”.
Use of Silk
All spiders can produce silk using specialized structures called spinnerets usually located at the far end of the abdomen. Tarantulas were reported to produce silk through their feet (tarsi) as well. Despite the universality of silk production, not all spiders use the silk to construct cobwebs.
Many spiders evolved different methods of using their silk, which include the use of silk-nets to catch prey (Deinopis sp.), silk trip-lines to sense prey (Liphistius sp.), silk “parachutes” for gliding long distances, silk safety lines as well as silken covers for sperms and eggs.
Spiders will immobilize their preys before biting them and injecting venom (apart from Uloborid spiders that do not have venom, they just bite hard). While the prey is paralysed, the spider will secrete digestive enzymes that will, as the name suggests, dissolve the prey into juices healthy for the spider.
Spiders are not known to attack and bite humans. Contrarily, they do bite only when threatened or provoked. Fortunately, to date there are no known venomous spiders here in Malaysia. Nevertheless, bites from large spiders will still inflict excruciating pain and cause inflammation and then infections if not treated properly.
Benefits to Humans
Spiders are efficient hunters or predators that help to keep the insect population in check. For example, Jumping Spiders (Salticidae) love to hunt and prey on a wide range of flies, most of which are annoying pests to humans. On the other hand, Huntsman Spiders, despite their scary looks, excel at hunting down cockroaches and even house geckos.
Different spiders produce different types of venom with potentially beneficial applications. On-going research are looking at using spider venom to treat heart-related problems, erectile dysfunction as well as Alzheimer’s diseases. Of course, venom of deadly spiders can be used to formulate antidotes.
The highly tensile spider silk are also being applied in the development of high-tech and lightweight bulletproof vests. The differences in property between spider silk and silkworm silk may promise more applications in the future, especially to the fabric industry.
In Cambodia, cooked tarantulas are also considered as a local delicacy.
There you go! A short and brief introduction on spiders just for you! We hope that you have learnt a bit more about spiders now, and know that they are actually not as evil and creepy as we thought. Still, in order to truly appreciate the wonderful diversity of Spiders, we welcome you to check out the Spider Pages!
Thank you for reading and have a nice day!
*For more info and guides on taking these type of Macro shots, please visit PixelsDimension.
* The authors attempted to make this article as simple as possible. Advanced topics will be included in the future.