Arthropods
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All arthropods have an exoskeleton, a segmented body, and jointed legs.
“Ex” is a Greek word that means “out of.” “Endon” is a Greek word that means “within.” Arthropods have an exoskeleton. Other animals, such as mammals, have an endoskeleton. What is an exoskeleton? Brainstorm some advantages and disadvantages of having an exoskeleton. + = protection – = must shed in order to grow What do arthropods eat? (decaying plants and animals, live plants, other arthropods, occasionally small mammals). How are arthropods important to other members of the food web? |
Arthropod hunt
Use the sweep nets (demonstrate proper sweeping technique) and look under rocks and bark to collect arthropods. Remember to respect their habitat and be gentle. Place the collected arthropods on the white viewing sheet. Open your field study notebooks to the arthropods pages. Choose an arthropod to examine. How many legs does it have? Does it have wings? Does it have antennae? Which of the five types of arthropods is it? What color is it? Where was it found? Draw the arthropod in your field study notebook. What might it eat? What parts of its habitat would it find useful? Use the field guides to identify it. Arthropods can be found everywhere, including in your home and yard. Think of some arthropods that humans find useful, and some arthropods that humans consider to be “pests.” What do humans do to control pests? Do these actions only affect the pests? Is it possible to control pests in a way that is safer for other plants, animals, and people? What are some changes you can make in your household to lessen your impact on the plants, animals, water, and soil in your community? |
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Insects
• 3 pairs of legs (six total) • 3 body segments • 1 or 2 pairs of wings • One pair of antennae Insects include beetles, ants, flies, bees, etc. Insects are the most numerous group of animals. There are more species of beetles than all other non-insect animal species combined. Insects have been around for 390 million years. The African Goliath Beetle is the heaviest insect in the world and weighs 100 grams (the same as 33 pennies). |
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Arachnids
• 4 pairs of legs (eight legs total) • 2 body segments • No wings • No antennae Spiders inject enzymes into prey that digest the insides. The spider then drinks the liquefied innards through hollow fangs. Arachnids include spiders, ticks, mites, and scorpions. The longest lived spiders are the tarantulas, some live up to 28 years. |
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Centipedes
• 1 pair of legs per body segment (total of two legs per body segment) • No wings • One pair of antennae Centipedes are carnivorous, they eat smaller insects. Centipedes have a poison gland to kill prey. The longest centipede in the world is the giant scolopenders of South America and Asia, which can reach up to 11 inches. |
Millipedes
• 2 pairs of legs per body segment (total of four legs per body segment)
• No wings
• One pair of antennae
Millipedes are herbivores and decomposers. They eat the forest duff layer and put nutrients back in the soil for plants to use and grow. They decompose 90% of the duff layer of soil. Millipedes have stink glands to repel predators and they curl into a tight ball when threatened. The millipede with the most legs lives in California and has 375 pairs of legs, that's 750 total legs!
• 2 pairs of legs per body segment (total of four legs per body segment)
• No wings
• One pair of antennae
Millipedes are herbivores and decomposers. They eat the forest duff layer and put nutrients back in the soil for plants to use and grow. They decompose 90% of the duff layer of soil. Millipedes have stink glands to repel predators and they curl into a tight ball when threatened. The millipede with the most legs lives in California and has 375 pairs of legs, that's 750 total legs!
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Crustaceans
• 5 or more pairs of legs (ten or more legs total) • No wings • 2 pair of antennae • Many body segments Crustaceans have specialized legs for walking, swimming, crushing, and for defense. Crustaceans include crabs, lobsters, barnacles and crayfish. The pill bug, or sow bug (sometimes called the potato bug) is the only land crustacean. |
Tips for teaching this station:
Remember, this is one of the few afternoon stations that cannot be done in the classroom. Take advantage of the nature!
Remember, this is one of the few afternoon stations that cannot be done in the classroom. Take advantage of the nature!
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Physical station layout:
Both arthropods stations have essentially the same layout. There is a big open space in the middle of the station with bunks around the edges. Encourage the students to sit on the floor along with you. Students sitting on beds have a harder time staying focused. The introduction to the basic types of arthropods can be done in the station, and the arthropod hunt should be done outside. If it is too rainy to be reasonably comfortable outside, then collect some bugs and bring them back into the station to view them. Learning arthropod types:
Pass out each arthropod card to a different student (or two cards each to pairs of students if you have some who don't read so well), and have them read the cards to themselves. They will be sharing the information with the rest of the group, so have them pick out their favorite fact from the paragraph at the bottom of the page. The students should share all of the bulleted part. As each student or pair of students shares the information, have the students do some sort of motion to represent what they are saying. This can be in the form of building a bug out of students, interpretive dance, etc. Be creative. |
Arthropod hunt:
Please keep the nets in good condition. Demonstrate how to use the sweep nets BEFORE handing them out to the students. The sweep nets are designed to knock arthropods off the bottoms of leaves. Hold the net open side up and shake it gently in a mass of sword ferns or other vegetation. It usually will not look like you have caught anything, but bring the net over to the white viewing sheet anyway. To empty the net, hold it open side down and turn the net completely inside out. The arthropods should fall to the viewing sheet where they can be seen easily. Some are very small; look carefully. After you have demonstrated the nets, you can hand them out. There are only three nets per station, and you will most likely have more than three students. As each student comes to the white viewing sheet to empty their net, hand their net to a student who currently does not have a net. While students do not have nets, they can look at what they found and try to identify them. When returning the nets to the station, place them on a top bunk in such a way that the fabric of the net hangs down so it can dry. |
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Identifying bugs:
Point out the arthropods on the white viewing sheet—especially the small ones that are hard to see so the students can find them. Ask the students which of the five categories of arthropods a particular bug falls into. If they don't know, help them get to a conclusion through counting legs and body segments. If they know instantly, "It's a spider!" ask them how they know. They should be able to tell you characteristics learned in the station, like number of legs, etc. The quick and easy guide is as follows: Insects = six legs, arachnids = eight legs, millipedes = lots of legs and curls up when frightened, centipedes = lots of legs and moves backward and forward with equivalent ease, crustaceans = you probably will not find any, but if you do they will be pill bugs or potato bugs. Bring the quick reference sheet and some field guides out with you for more specific identifications. |
Timing:
Spend some time on learning the different types of arthropods—at least enough time that you are confident your students can distinguish between some of them from memory and all of them with the use of the cards. For the arthropod hunt, make sure every student gets a chance with the net, and continue as long as they are focused on the task at hand and are still interested in arthropods, but not more than a half hour for the total station. |
Additional Resources
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