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Background

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Did you know that there are many more kinds of insects on earth than any other kind of living creature? It's hard to imagine, but 95% of all the animal species on the earth are insects! Millions of insects can exist in a single acre of land!  Scientists have discovered over one million species, and they think that there might be ten times that many that haven't been named yet!

They are divided up into 32 orders, or groups of insects. The largest order is the beetles (Coleoptera) with 125 different families and around 500,000 different species. In fact, one out of every four animals on Earth is a beetle. Scientists estimate that 10% of the animal biomass of the world is ants, and another 10% is termites. This means that 'social insects' probably make up an incredible 20% of the total animal biomass of this planet!

Insects eat more plants than all the other creatures on earth! They are also so important in the breakdown of plant and animal matter, that without them, we would have a world covered with dead plants and animals! In addition to all of this, insects are a major food source for many other animals.

All insects must have:
•    3 body parts - a head, thorax, and abdomen
•    6 jointed legs
•    2 antennae to sense the world around them
•    an exoskeleton (outside skeleton)

If all four of these things are not true, then the animal can't be called an insect! Spiders are not insects because they have eight legs and don't have three body parts. Centipedes and millipedes have way too many legs to be called insects! Most insects have one or two pairs of wings, but wings aren't necessary to be classified as an insect.

Insects have 3 main parts: head, thorax, and abdomen.

The head is used mainly for eating, sensing things, and gathering information.  Insect mouthparts have evolved for chewing (beetles, caterpillars), piercing-sucking (aphids, bugs), sponging (flies), sucking (moths), rasping-sucking (thrips), cutting-sponging (biting flies), and chewing-lapping (wasps). That's a lot of ways to eat! ?All insects have two antennae that they use to sense the world around them. Whether their antennae are short, long, thick or thin, insects use them to feel, smell, and even taste!

The thorax protects the body and gives support for the three pairs of jointed legs and, on many insects, for one or two pairs of wings. The legs may be adapted for running, grasping, digging, or swimming.

The abdomen contains the organs used for digestion and reproduction.
Insect Growth and Development (Metamorphosis)
Insects usually go through four separate life stages: egg, larva or nymph, pupa, and adult. Eggs are laid one at a time or in masses, in or on plants, or even inside another insect! Eventually a larva or nymph emerges from the egg. There are usually several larval or nymphal stages, called instars. During each stage the nymph grows larger and molts, or sheds its outer skin before the next stage. They grow the most during the last one or two instars, or stages. All the growing happens during the larval or nymphal stages. The eggs, pupae, and adults don't grow in size.

Source: http://www.ivyhall.district96.k12.il.us/4th/KKHP/1INSECTS/buginfo.html.

Vocabulary

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Attention Grabber

Ask students to name some animals.  (They will have quite a lot!) Using the pie chart (Download Materials) for a visual (with 95% insects, and 5% other animal species), show the students that most of the animals on Earth are insects!

Garden Activity   

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Part 1-Making an Aspirator

• To make an aspirator, also known as a pooter, you will need:
  • Jar with a lid (the lid must have 2 holes)
  • Tubing (rubber tubing works best)
  • Small screen (pantyhose is a great, cheap option)
• See the picture below to help build the aspirator.  
• Be sure to place a small screen (or pantyhose) between the hose that will be used to suck on and the jar!  (If there is no screen, students may swallow the bugs!!!!)
• Note that the size of the tubing will limit the size of insects that can be captured.  

Part 2-Bug Collection and Comparison

• Brainstorm with the students possible areas that would be good to collect bugs.  Good areas to look are under rocks, under tree branches, bark, wood chips, along fences, and near compost.
• Using these areas, choose two areas to compare.  Split the class into two groups.  (Note:  this can also be done using two different environments.  E.g., light areas v. dark areas, wet v. dry)  GO COLLECTING!
• Give students magnifying lenses to examine the bugs they caught.  Have students write descriptions or draw pictures of their findings. Students should also record the number of insects they find in their area! (See attached “Bugs, Bugs, Everywhere!” student handout)
• As students examine the insects, explain what is required to call an animal an insect.  (See Background section above)
• Release the insects back to their appropriate homes. 
• As a class, compile the data of the two areas.  Compare these results. 
• Create a line graph using the numerical data.  The type of insect on the X-axis and the number of insects on the Y-axis.  Each area will have a different line color. 
• Have students make conclusions based on the graph.

Wrap Up 

• Have students create their own insect! 
  
  • Some potential “must-haves” for their insects:  3 body segments, 6 legs, exoskeleton, 2 antennae, habitat, protection, food, and camouflage.  (Note:  use science concepts from past lessons!)

What's Next?

• Visit a butterfly garden make your own in the outdoor classroom

Download Materials

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Lesson Materials

Insect Pie Chart 

Student Worksheet

Bugs, Bugs, Everywhere