Presentation on theme: "A detailed insight into spiders. Many people think of spiders as these small, fast and deadly creatures that hide in our baths and lurk in dark corners,"— Presentation transcript:
A detailed insight into spiders
Many people think of spiders as these small, fast and deadly creatures that hide in our baths and lurk in dark corners, waiting to pounce. In fact, what I have just described is entirely wrong, and whilst they are often found in our baths and often in our houses and gardens, they are, in fact, more scared of us they we are of them! Many people see spiders as these eight-eyed monstrosities with sharp fangs that deliver a venomous bite. Yet you may be surprised to know that there are only about 30 kinds of spider that are dangerous to people, and only a few of these live in the United Kingdom. Spiders are actually more amazing than scary. They have many different and fascinating ways to catch their prey, such as hunting, jumping, fishing and even spitting! There are even spiders that look like crabs, ants and wasps! This presentation provides a detailed insight into spiders, and hopefully, by the end of it, you will be in awe of these great little critters, rather than absolutely paranoid about them!
Spiders are often confused with insects, when in fact they belong to a completely different group, known as Arachnids (these are also scorpions, ticks, harvestmen and mites). You can differentiate between a spider and an insect through a few key differences: A spider has eight legs, but an insect only has six. A spider’s body is made of only two parts (cephalothorax and abdomen) whilst an insect’s is made of three parts (head, thorax and abdomen). A spider typically has eight eyes (some have six) whilst insects usually have two eyes. Many insects have wings and antennae, but spiders do not. Spiders use a pair of furry “feelers” called palps for holding their food. The front part of a spider is called the cephalothorax – basically it’s head and chest. The body is covered by a tough, hard skin called an exoskeleton. The spider’s jaws, or fangs (officially known as chelicerae) are used to bite and crush their prey. Each ends in a fang that injects poison. The rear part of the spider is called the abdomen. It is not covered by the exoskeleton, and instead by a soft, stretchy skin. The spider’s eight legs are joined to the cephalothorax.
Ok, so it is fair to say that I am trying to convince you that spiders really are not as bad as many people think, but there is no denying it – some spiders are HUGE! The biggest spider in the world, the Giant Huntsman, is as big as a dinner plate! However, others are miniscule, perhaps the size of a pinhead. Apart from size, spiders also vary greatly in appearance. Fair enough; many spiders are your typical dull brown or grey colour, but others are a striking combination of yellows, reds and oranges. Some spiders have short, wide bodies, while others are long, thin and skinny. There are round spiders, flat spiders and spiders with spines, warts and horns. Spiders really are wonderful creatures! ( ) You may look at this strange little creature in the picture and think to yourself “what in the name of all that’s holy is that?” It is in fact, the aptly named Kite spider (Gasteracantha). This strange spider is found in Central and North America, as far north as California and as far south as Jamaica, in gardens and parks. Only the females have the striking colours, and are also much bigger than the males, typically around 8 mm in length, and 12 mm wide. They have six sharp spines protruding from their abdomen that look a lot like horns. No one knows quite what these strange spines are for, but they may make it difficult for predators to hold or swallow the spider.
The following picture is not an attempt to scaremonger. I am merely trying to demonstrate to you the pure beauty of the Wolf Spider – AKA The Master Hunter. If you are terrified of spiders...... (if you are then I don’t really know why you are viewing this presentation) then double click the screen now (and obviously look away whilst doing so)........
The wolf spider has eight eyes – 2 big eyes, 2 medium eyes and 4 small eyes. This gives the spider good vision as it hunts during the night Two large chelicerae (fangs) means the spider can hunt large prey The strong exoskeleton gives the spider a good defence against its predators Despite possessing the dull brown or grey colouration I mentioned earlier, please do not be fooled by the colouration of this spider, as it actually acts in their favour, as camouflage! The eloquently named Wolf spider is a mean nocturnal hunter, and possesses all the characteristics that make it so. They are robust, agile hunters They don’t have time to spin little pathetic webs! They’re not wusses! No, they CHASE after their prey! They are capable of defensive bites that are suited to their hunting but are generally not harmful to humans To get a further insight into Wolf Spiders, click the link below for a short video... http://www.youtube.com/watch?v=v6M_84t3oa4
The fishing spider (Dolomedes fimbriatus) floats on the surface of water to catch it’s prey of fish and frogs. It’s long legs spread its weight over the surface so that it does not sink. Spiders, among other things, are renown for their rapid speed. However, these are often quick bursts of speed as spiders are soon out of breath. This is perhaps the main method of movement for a spider. Spiders can walk, run, jump, skate, climb and hang upside down. Each spider’s legs have seven separate sections, powered by sets of muscles and blood pressure. At the end of each leg are two or three sharp, toothed claws for gripping surfaces. Spiders that spin webs have a special, hooked claw to help them hold on to their webs. Hunting spiders have furry tufts of hair between the claws for gripping smooth surfaces and for holding prey.
Aren’t they just the cutest thing? Awwwwwww. You may say that the most remarkable thing about this innocent jumping spider is it’s sweet little eyes...... and, to be fair, it sort of is. However, another very commendable thing about this spider is it’s hunting technique – it traverses across leaves by jumping! It is also how it catches it’s prey. Jumping spiders are active hunters, which means that they do not rely on a web to catch their prey, which is usually insects. They use their clever camouflage to blend in with the surroundings, and lie in wait for their prey, ready to pounce. They use their superior eyesight to spot their prey, then they pounce and deliver a venomous bite. The venom acts very quickly, giving it’s prey little time to react. To get a further insight into Jumping Spiders, click the link below: http://www.youtube.com/watch?v=Xwmgg7GDWJ4&feature=fvst
This female golden orb weaver is not only known for her size, but for the intricacy of her orb-shaped web. The spider’s body alone grows up to 2 inches, but the size of it’s actual web is drastic – perhaps even three times bigger than it’s maker! Whilst all spiders produce silk, not all spiders spin webs. A few spiders go fishing for their food instead. The net-casting spider throws a strong, stretchy net over it’s prey. The bolas spider is very unusual in that it traps insects by swinging a thin line of silk with a sticky ball on the end, like the fishing hook on the end of a line. Spitting spiders are even more cunning. They fire a poisonous “glue”-like substance to pin their prey to the ground.
No matter how many times you look at pictures of this unique spider, you always feel creeped out at it’s ominous face and it’s long, spindly legs. Nevertheless, the hunting method of this creature is something to admire. The spider builds a small, round-like web that it suspends in mid-air between it’s front legs. It usually positions itself in mid-air above a leaf or a branch, waiting to pounce. When prey approaches, the spider will stretch the net to two or three times its normal size and pounce onto the prey from above, entangling it in the web. Their excellent night-vision is provided by two large eyes. These eyes are so large in comparison to the other six eyes that the spider seems to have only two eyes. To see a video on a net-casting spider catching it’s prey, click the link below: http://www.youtube.com/watch?v=-AjFHPy3cx8
Some spiders do not spin webs, nor do they go out hunting for food. These spiders prefer to build and wait inside underground burrows or tubes of silk and wait for prey to approach and pass by. Silk threads placed carefully around the entrance to the burrow vibrate when an insect or other small creature such as a mouse passes over them. Inside the burrow, the spider is waiting, concealed in a shadow of darkness. The spider feels this vibration on the silk threads, giving it the indication that it’s prey is nearby. This gives it the opportunity to rush out of its burrow and pounce of the prey before it can escape. It then drags its prey back into the burrow, where it is killed and later devoured. How pleasant.
The trapdoor spider is the master of disguise, the artist of deception, the creator of craftiness. It is the designer of..... well you get the picture. Whatever you call it, this spider is one mean brute. This spider does not spin a web, nor does it hunt. Instead, it builds a crafty burrow with a trapdoor, and places silken threads around it’s burrow which act as trip lines. These detect the movements of a passing insect or creature, and gives the trapdoor spider it’s opportunity to pounce, rushing out of it’s burrow to grab the prey with it’s jaws and drag it back down. Trapdoor spiders remain fiercely loyal to their burrows, and live in them for up to 20 years! To get a further insight into Trapdoor spiders, click the link below: http://www.youtube.com/watch?v=7yJgPVxS5aI
I can imagine that by this time you have viewed most of my presentation and the idea of spiders being AWESOME is pretty much now ingrained into your brain. But I can also understand that your getting a little bit tired. Not to worry! This slide will liven things up a bit! No doubt the forefront of your minds throughout this presentation has been that of a spider’s venomous bite. Nearly all spiders use poison to kill or paralyse their prey and for defence. There are two main kinds of venom that can have serious effects on humans – one is neurotoxin, which acts as a nerve poison which attacks the nervous system, paralysing victims quickly. This type of venom is produced by the widow spiders, most notably the black widow spider (Lactrodectus). The other kind of venom works more slowly, destroying tissues and causing necrosis, ulcers and gangrene. This is produced by the recluse spiders, most notably the brown recluse spider (Loxosceles). Both of these spiders are found in the United Kingdom, so be afraid!
You may look at this spider and be fooled into thinking that it looks terrifying. Well, the truth is.... your right; it doesn’t just look terrifying, the way in which it lives is terrifying! This is the Brazilian Wandering Spider, the master of cunning, the creator of..... ok I’m not starting this again. This spider is a large hunting spider that, according to the Guinness Book of Records, produces the most toxic of all spider venoms. It is also notoriously aggressive. If disturbed, it raises it’s front legs above it’s head to expose it’s threatening jaws. Then what? Does it run? No. Even if this spider is confronted by a foe much bigger than itself, it will CHASE AFTER the foe until it flees. Luckily for most people, the Brazilian Wandering Spider roams the Amazon Jungle in...... Brazil (Yep....go figure), so people in the UK can go to bed at night knowing you’ll be safe. If you live in Brazil, then you’ll more than likely know about this spider, seeing as it’s accountable for around half of all recorded deaths as a result of spider bites in Brazil each year. To get a further insight into Brazilian Wandering Spiders, click on the link below: http://www.youtube.com/watch?v=noLn2gK3fzY
Judging by the last slide, you would think that the need for a spider to defend itself is quite pointless. Truth is, not all spiders are massive, powerful hunters like Mr. Wanderer of the previous slide. Spiders are typically small, with soft bodies that make a tasty snack for many predators. To avoid predators, such as other spiders, hunting wasps, lizards and frogs, many spiders hide. Other spiders conceal themselves by being beautifully camouflaged to blend in with their surroundings. In complete contrast, some spiders copy the bright colours of dangerous predators, such as wasps. This tricks predators into leaving the spider alone. Spiders will even play dead, since predators prefer to eat live prey. This is the seven-spined crab spider (Epicadus heterogaster). The fleshy lobes on it’s abdomen imitate the white flowers of the plant it dwells on. This helps it to blend in with its surroundings and avoid detection by predators.
I know I’ve covered some pretty insane spiders in this presentation, but there is no denying the ingenious way in which this spider avoids predation. This is the aptly named Golden Wheel Spider, a spider that lives on the sand dunes of the Namib Desert in Africa. You may think that it’s gold colour helps it blend in with it’s surroundings, but this spider has another method of escaping from its predators. If caught out in the open, however, the spider rears up to make itself look larger and more frightening to enemies. If that doesn’t work, then it has another remarkable way of escaping. The spider throws itself sideways, pulls in its legs and rolls itself into a ball. It then cartwheels rapidly away down the dunes, escaping from it’s prey. To see a video on this great escape, click on the link below: http://www.youtube.com/watch?v=ozn31QBOHtk
For me, it’s been a long day of creating presentations, for you, a long day of viewing them. So, I’ll keep this short and sweet. SPIDERS ARE COOL! STOP BEING COWARDS! THEY ARE A VALID PART OF OUR ECO-SYSTEM AND WITHOUT THEM IT WOULD FALL APART. THIS VIDEO MAY HAVE BEEN HUMOUROUS, BUT IT IS ALSO HERE TO EDUCATE. PLEASE, THE NEXT TIME YOU SEE A SPIDER, THINK BEFORE YOU ACT! LET IT SEE THE LIGHT OF DAY AND THE FEELING OF THE LIGHT BREEZE RATHER THAN THE UNDERSIDE OF YOUR BOOT AND A POOL OF IT’S OWN BLOOD TO DROWN IN. TREAT IT WITH RESPECT, AND DON’T SCREAM, COS THEN IT WILL JUST BITE YOU. YOUR FAULT REALLY. HA. HAHA. HAHAHA. Anyway, that’s it really. A short conclusion outlying the main point of my presentation.