A Little Bit More
If we were to shrink to the size of a typical insect, think how our point of view would be altered! Life at this level would be a constant danger, like living surrounded by hungry lions and tigers. Spiders are some of the most numerous organisms in the world, and ounce for ounce they rank right up there with the most ferocious predators on earth.
Despite their fierce appearance, spiders lack true biting mouthparts. Instead, they grasp and puncture their prey using their paired chelicerae. All spiders are predators and feed mainly on insects, although some of the largest spiders may also feed on small vertebrates. Different spiders capture their prey in different ways: wolf and jumping spiders search out and pounce on their prey, crab spiders lie concealed on flowers and wait for insects to approach, but the majority of spiders spin webs and wait for insects to blunder into their traps.
Finding out what the spiders are eating is often an easy matter of simply examining the remains of the victims’ exoskeletons lying beneath their webs. Once the internal organs have been digested and sucked out of an insect, its empty shell is usually cut out of the web and falls to the ground.
Activities
Close-Up
Objectives: Heighten observational skills
Materials: Digital camera, ability to crop and print out photos
Since we’ve been talking about a close-up of a spider, I thought it would be fun to continue with this approach. A really interesting exercise in observational skills involves taking close-up photos of “everyday” objects and then printing them out for identification. It’s amazing how difficult this can be even though the objects may be those you see every day – one needs to be a good observer.
Not all schools have student access to a digital camera so you may need to provide the photos yourself, rather than have the students take the photographs.
Example- toothbrush closeup
1. Assign each student the task of obtaining one photograph of something that is part of their “everyday world”. This might be a toothbrush, a dinner fork, a plant leaf, a computer key, a fingernail – you get the picture. Subjects should all be things that everyone can recognize.
2. If you assign this exercise at school, you might want to have each student acquire his/her digital photo at recess when the others are not around. The idea here is to have each student shoot or crop a “part” of a subject so it’s not immediately obvious what it is. (ie. if you were shooting a toothbrush, you might need to shoot the entire brush for the sake of the focus but then crop just the bristles so it isn’t immediately obvious what you’re seeing).
3. As the photos are obtained, print each one out (crop as necessary) in black & white on 8 ½ X 10” paper, number each on the front and place the student’s name on the back.
4. Once all of the photos are obtained and printed, have a viewing day in which students try to identify what they’re seeing. Each student should number their paper from 1 – whatever, and then see if they can name the objects photographed.
5. To make this extra fun, tell the students that they’re going to do this exercise the way college students take lab exams in college. Have each student go to one of the numbered photos (there should be as many photographs as there are students) and begin answering the photo questions at the question number on which they are located. (ie. If a student starts at photo #6, he/she begins answering on line #6 and then moves to question #7 next.) Give each station 30 seconds or whatever you deem appropriate and have them move to the next numbered station at the sound of a buzzer/bell/whatever.
6. Once complete, it should be fun to go over their answers to see how people did. You might be surprised at how difficult this can be. Those students with better observational skills will do best.
Key Concepts
Structures and Functions, Predator/Prey Relationships
Questions
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Posted by mel khalil on April 26, 2006 at 04:19 AM
Q: What is the population of spiders in australia? can you plz tell me so i can finish my english project!!!!!!!!!!!!!!!!
A: No one can answer that question unless they could count each and every one! What people can do is estimate, and I emphasize the word estimate,the number of spiders in an acre or hectare (not sure if you use acres in Australia)and then multiply by the number of acres in the country. This would give you a very, very rough estimate of what you might expect. Sorry, but I can't do better than that. Get back to me if I can help further.
Posted by Dan Sokolnicki on January 10, 2006 at 10:40 PM
Q: I've heard that there are no known deaths caused by tarantulas, is that true?
A: That sounds true to me. Both the Black Widow and Brown Recluse are known to have an especially dangerous venom but even they rarely kill anyone. ALL spiders have venom but only those two species are known to have caused a death in North America. Thanks for asking.
Posted by Willem on March 20, 2005 at 11:48 PM
Q: do spiders see in colour
A: Although most spiders do not have good vision, the jumping spiders see quite well and use their vision to help them hunt down and capture prey. It is believed that jumping spiders do have some color vision in at least some of their eight eyes.
Posted by cambell on March 13, 2005 at 05:54 PM
Q: Do spiders hunt at day more than at night?
A: This depends on the species involved. Many spiders are active at night, such as the nocturnal orb weavers, many hunt during the day, such as the jumping spiders, and many others may be active almost anytime.
Posted by cambell on March 08, 2005 at 07:46 PM
Q: Do spiders have noses? Some of the class thinks they do, but the rest think they don't.
A: Spiders do NOT have noses. Spiders receive air through small openings into their abdomen, not their head.
Posted by Matthew on March 07, 2005 at 11:35 PM
Q: Do spiders attack humans on purpose?.
A: Although there are lots of stories about spiders and their behavior, I don't know of any reliable information about a spider actually attacking a human. If you think about it for a moment, it just doesn't make sense - there is nothing in it for the spider. Spiders will, however, bite if threatened. As a child, I picked up a spider once and it immediately bit me. I dropped it and it ran away - pretty good defensive strategy. Many, many animals will bite if threatened as it's often their only defense.
Posted by cambell on March 07, 2005 at 08:32 PM
Q: what species of spider has wounded or killed the most humans?
A: This is a difficult one if we look at spiders from all over the world but I can answer this for North America. In North America there are only two species, the Brown Recluse and the Black Widow, that have been known to cause death in humans. Apparently their venom is quite potent and some people, not everyone, are especially allergic to the venom and it may cause death. The number of deaths, due to spiders is extremely small and certainly no cause for widespread killing of spiders.
Posted by cambell on March 07, 2005 at 08:13 PM
Q: how do spiders communicate?
A: There are two different ways that come to mind about spider communication, although I'm sure there are many more. Many of the web-making spiders communicate with one another by vibrating the web. When a male spider enters the web of a female, he vibrates the web in a certain way to let her know he is there. As you can imagine, it's important for him not to vibrate the web like a struggling insect or he'll be captured and bitten. Those spiders with reasonably good eyesight, like the jumping spiders and tarantulas, have pedipalps, kind of like feelers or antennae, that they use to communicate. Males of these kinds of spiders have larger pedipalps than the females and they wave these about in a certain way to communicate with a female. If you can find a book on spiders, look to see if you can tell the males from the females by looking for pedipalps - the males have larger ones than the females.
Posted by Sam on March 07, 2005 at 08:05 PM
Q: Are some spiders blind?
A: To the best of my knowledge, there are no blind spiders, however most spiders don't see all that well. The typical spider, those that make webs and wait for prey to blunder into their webs, don't see very well and actually don't need to. Those spiders that hunt down their prey, like jumping spiders, tarantulas, and wolf spiders, do have pretty good eyesight
Posted by Sam on March 07, 2005 at 07:54 PM
Q: how many native spiders are there in Australia
A: Now there's a difficult question! I'd have to get a field guide to spiders of Australia and count up the number included. I'm not sure where you live, but if it's Australia, see if you can find a field guide on Australian spiders. I live in North America and I don't have a clue to how many we have here - I'll bet the number is quite high!
Posted by cambell on March 07, 2005 at 07:47 PM
Q: whats a spiders most powerful wepon
A: I think it is easy to say that a spider's venom is its most powerful weapon. Although spiders are small, compared to humans, there are some whose injection of venom can cause extreme pain or even death, in a few cases.
Posted by Jazz on March 04, 2005 at 01:47 AM
Q: what do people kill spiders for
A: People tend to kill the things they fear and many people are afraid of spiders. It's really too bad since spiders have an important role in keeping insect numbers in check. I don't especially like to have spider webs in my house so I simply take spiders outside and release them.