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Learning Objectives

The student will be able to:

1. list the characteristics that all insects have in common.

2. distinguish between the orders of insects using characteristics unique to each group.

3. understand how specific body structures help insects survive.

4. understand the life cycle of insects, including complete and incomplete metamporphosis.

5. utilize a variety of methods to collect insects.

  Laboratory Description
Insects are the most numerous group of animals on this planet, making up about 80% of all animals. In fact, there are more species of insects than all other species of living things. On one tree in the Amazon rainforest scientists identified over 2,000 different species of insects. They play essential roles in the balance of nature as predators, food for other animals and scavengers.

During today’s lab, students will explore the fascinating world of insects. Students will start out collecting aquatic insects from a local stream. As they sort their specimens, they will encounter a variety of stages in the life cycle of some common insects. They will observe the unique adaptations that allow some insects to survive in the water during the initial stages of life and then on land as an adult. Students will learn how to collect live insects for study at home.


What is an insect?
Insects belong to the phylum Arthropoda. Like all arthropods, they possess a hard exoskeleton on the outside of their bodies for protection and support. They have jointed legs and segmented bodies.

Insects are divided into three segments – the head, thorax and abdomen. Insects have three pairs of jointed legs attached to the thorax. One pair of antennae is attached to the head region for feeling, smelling and communication. Most insects have two pairs of wings, but some do not.

  Insects respire through tiny openings called spiracles. Air passes in and out of the spiracles to and from a network of tubes in the insect’s abdomen. A Madagascar Hissing Cockroach can push air through these spiracles quickly, making a hissing noise to scare off potential predators.



Create Your Own
Insect Collection!

Gather road kills or catch live insects to put in a killing jar. This can be made using a wide-mouthed jar with a lid and adding a paper towel soaked in fingernail polish remover containing acetone. More information about spreading and mounting insects can be found in the books referenced in the “Further Explorations” section.

Always label the insects with the collector’s name, location and date. Identify the specimen using a field guide. To learn more about the specimens you’ve collected, do some research. You might be surprised to learn about their amazing abilities. List the adaptations each insect has for survival, including protection, feeding mechanisms and movement.

Insect Body Parts:

Amazing Mouthparts
An insect’s mouthparts are a clue to what it eats. How? The mouthpart is made especially for the type of food the insect eats. Butterflies have mouthparts formed like a straw for sucking nectar from flowers. Flies have mouthparts formed like a sponge to soak up liquids. Mosquitoes have needle-like mouthparts for piercing skin before sucking blood. Grasshoppers have mouthparts similar to a human’s mouth to help chew plants.


Look at Those Legs
Take a look at an insect’s legs to learn about its lifestyle. Often you can use the legs to learn where an insect lives, how it moves about or how it defends itself. Mole crickets have muscular legs with claw-like structures at the end for digging underground. Grasshoppers have legs that are elongated and muscular for jumping. Spikes cover a cockroach’s legs to enable it to climb and to protect it from predators.

Just Flying Around
Wings are very important to insects as a method of locomotion. They have helped to make insects the most successful animal on earth. Very few other animals can fly. Flying helps insects escape predators and move from place to place, thus broadening the space they can inhabit. However, not all insects have wings.

 

Survival of the Fittest

Insects can be considered the most dominant life form on earth. Special body parts enable insects to survive in environments normally considered to harsh for survival.

Size is a great asset to an insect. Its small size allows it to move about without being noticed by many larger animals. Flight enables many insects to move quickly away from predators. Insects also avoid danger by hiding. Insects’ bodies are camouflaged using colors and patterns to help blend in with its surroundings. Some insects have body shapes that make them look like leaves or twigs. Some go so far as to sway gently to mimic a leaf blowing in the wind.

Many insects are brightly-colored. Some insects are advertising an unpleasant experience to potential predators. “Don’t eat me – I taste bad, have sharp spines or will sting you.” Other insects mimic the coloration of a distasteful insect hoping to discourage potential predators. Still others are trying to look pretty to attract a mate.

  Insect Senses:

Antennae
An insect’s sense of smell is keener than anything we can imagine. They smell primarily with their antennae. Segmented, flexible and covered with many tiny hairs, antennae can come in many shapes and sizes. They all function to detect chemical cues in the air.

Eyes
Insects have two large compound eyes that consist of thousands of tiny lenses shaped like honeycomb cells. These eyes are usually large and located on the sides of the insect’s head. They are excellent motion detectors – try sneaking up on a fly!

Sound
Many insects can emit sounds by rubbing their appendages together or vibrating a membrane. Have you ever heard a cricket chirp or a cicada sing on a summer night? Insects “hear” these sounds as membranes vibrate in response to sound waves, however these membranes are not located in ears, but on the abdomen or forelegs.


Life Cycles
The life cycles of insects usually involve a process called metamorphosis, a change from one life form to another. Frogs, toads and salamanders also undergo this big change. It is widely believed that metamorphosis benefits the insect because the juvenile is not competing with the adult for a food source – they eat different types of food.





Some insects undergo incomplete metamorphosis. As the insect matures, it increases in size and develops reproductive organs and wings. For most species, the immature insect, or nymph, looks similar to the adult. However, some nymphs are aquatic and do not resemble their terrestrial adult forms. Examples of these aquatic insects are dragonflies and mayflies.



Other insects undergo a major change in their forms as they grow in a four-stage change called complete metamorphosis. From the egg hatches the larva, whose primary functions are to eat and grow. The larvae are worm-like in appearance and do not resemble the adults. Larvae molt several times as they grow. The last molt results in a pupal form. The pupa does not eat, and its movement is restricted to no more than a wiggle. During this stage, a great transformation is occurring as tissues are broken down and reassembled. The pupal stage can last from four days to several months. The adult emerges from the pupa, completely different from the larval form. Its wings are crumpled and body soft. Within hours, the wings become stronger and the body hardens. The adult stage can last from a few hours to several years. An adult’s primary mission is mating and egg-laying.

Try This at Home!

Insect Behavior
Catching insects to observe is easy if you just look closely! Always watch the insect you’ve discovered for a few moments before catching it. You will learn more by combining an observation of its natural behavior with up-close observations.

Remember, be careful when catching insects – some may sting or bite. After observing them in your jar, release them in the spot where you found them.

Below are some experiments that you can do in your own backyard. Always check with an adult so they are aware of your experiments and can monitor your safety.
Further explorations
The following science books are available for use in the ELL. Each has excellent, easy to understand information about insects and suggested activities. Books may not be checked out, however you are welcome to make copies.


The Insect Appreciation Digest by Tom Turpin, 1992. This book tells you “everything you ought to know about insects (that your parents didn’t teach you).” Written in a delightful manner, this book gives the basics of insect characteristics and is filled with fascinating stories about the lives of insects. You can’t resist reading about insects that multiply, sticks that walk and insect antifreeze!

The Practical Entomologist by Rick Imes, 1992. Beginning with the basics, this guide describes what characterizes an insect, including anatomy and the life cycle. It takes an order-by-order look at insects, explaining how each group differs from the others.

The Insect Almanac by Monica Russo, 1991. Meet the tiny creatures who share your backyard and learn how they live, how they breed and what they eat. Learn how to hunt for insects and which ones you will find during all seasons of the year. Try the many activities suggested throughout the book.



Beetle Trap
Place a small jar into the ground so the mouth is even with the ground. Bait the jar with a small piece of raw meat at the end of the day and check your jar in the morning – most beetles are active at night. Add new bait every few days and empty it if it rains.

Pitfall Trap
Web Sites
The following web sites would be helpful in any study of insects. They are packed with interesting information and activities to try!

Take a tour of some of the creepy crawlies you love to hate on the Yuckiest Site on the Internet. Wendell, ace worm reporter, will tell you all about his amazing buggy friends, especially his frequently squished pal, the roach.
http://www.yucky.com

Sonoran Arthropod Studies Institute web page includes a virtual arthropod zoo with photos and information. visit the Arthropod Zoo and take a look at how to classify arthropods.
http://www.sasionline.org/

 

To protect your trap from other animals, cover the mouth with a board, propped up slightly with a small stone. Choose areas near piles of wood, rotten logs, or shrubs or choose wet wooded spots. Areas near buildings also work well.

The Fallen Log
It’s amazing how many things live in and on rotting logs. Learn about insects and their roles in decomposition as you explore life in a rotten log. Before searching for your log, research the process of decomposition.

Rotten Log

Next, locate a rotten log and carefully begin inspecting it. Note any markings or holes found on the log’s exterior. Many beetles can create beautiful patterns as they bore into the wood. Pull apart the log. You should encounter many insects and other arthropods such as spiders. Be sure to make drawings and to note characteristics of each organism you see. Use these notes to identify the animals later using a field guide.

Hula Hoop Population Count

How many insects make their homes in your backyard? If you really want to know, you can do a simple population count. Throw a hula hoop randomly in your yard and count the number of insects within the hoop’s boundary. Remember to look closely - many of the insects are tiny. When finished, graph the results.

If you found these results interesting, you might want to do comparison studies. Toss the hula hoop into a garden area or an area with leaf litter. Compare areas under or near trees to areas in the full sun. An endless number of comparisons can be made. Graph the results. Are they similar to what you expected to find?
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