Bug Work

Adapted from "Prairie Insects" by the Illinois Natural Heritage Society

Lesson Introduction

Some of the most common prairie insects include ants, bees, wasps, grasshoppers, dragonflies, termites, beetles, aphids, butterflies, moths and flies. Insects exist on the prairie in many forms. They all begin as immature nymphs or larva. Nymphs look like smaller versions of their parents until they undergo a series of molts to reach their adult size. Nymph to adult development is called incomplete metamorphosis. Larvae look nothing like their parents. They molt but then rest as a pupa, often in a cocoon, until they emerge as an adult. This process is known as complete metamorphosis. The prairie ecosystem could not exist without the important work insects do. They pollinate, decompose dead plant material and aerate the soil.

Illinois State Goal	Standard	Learning Benchmarks
12	A	2a. Describe simple life cycles of plants and animals and the similarities and differences in their offspring.
12	B	2a. Describe relationships among various organisms in their environment.

Lesson Objectives

The students will:

• define the terms incomplete and complete metamorphosis
• examine insect roles within prairie ecosystems

Time Allotment

45-60 minute class period

Materials

(optional) pictures of the following prairie insects - Contact the Illinois Department of Conservation education department for free posters and pictures at (217)524-4126: flesh fly, robber fly, least skipper butterfly, painted lady butterfly, spotted cucumber beetle, digger wasp, aphids, praying mantis, least skipper caterpillar, tumble bug

PROCEDURE

Tap Prior Knowledge/Share with Neighbor

1. Ask for a volunteer to come to the front of the class. Call this student "Butterfly larvae." Ask the class what this butterfly larva is more commonly known as (a caterpillar). Have the caterpillar pretend to eat leaves. As they eat leaf after leaf they get bigger. Attach two or three other students to the caterpillar body to simulate growth.
2. Ask the students what happens when the caterpillar is ready to metamorphose. They become a pupa. Have the students portraying the caterpillar bunch together. Ask three or four other students to circle the caterpillar tightly. They are the pupa.
3. Tell the students that the conditions are right for the pupa to metamorphose. It is warm enough and there is plenty of nectar for the emerging being. What will emerge from the pupa?
4. Have all of the students sit on the floor, portraying the disappearance of the pupa. Have the first student fly out of the circle as an adult butterfly. Tell the students that they have just portrayed complete metamorphosis. 5. Ask if anyone can guess what incomplete metamorphosis might be. Incomplete metamorphosis is when the nymph or baby insect is merely a smaller version of the adult. It needs to shed several times during its lifetime in order to grow into an adult.

Hands-on Activity

6. Tell students that insects at all stages of life are important within the prairie ecosystem. Some of the tasks include pollination (#1), food processing (#2), decomposition of dead plant and animal material (#3), and soil tillage (#4). Have the students read the Case Examples in order to define what these jobs entail.

Case Examples

#1- Pollination: The gold and black bumble bee pollinates many of the prairie plants. Pollination is when wind or insects carry pollen from the male part of flowers to the female part of other flowers. Insects like the honey bee, often unknowingly collect the pollen on their legs when they land to feed from the nectar of a flower. The pollen fertilizes the seeds inside the ovary of the female flower, and the flower matures. Most prairie forbs depend upon the hungry insects to move pollen about the prairie and assist in their reproduction and survival.
#2- Food Processing: The red legged grasshopper eats the grass and leaves of forbs. With the plant food it eats, the grasshopper builds the tissues in its body. Eventually the insect will be preyed upon by another animal like an amphibian. When this happens, the food energy that was once in the plant parts the grasshopper ate, is transferred to the toad. This grasshopper and many other insects process plant food into themselves and then become food for other animals. Without them their predators would not survive.
#3- Decomposition of Dead Plant and Animal Materials: The American carrion beetle flies about the prairie and locates a dead animal by scent. The adult lands beside the body and crawls into the soil beneath it and lays eggs. The eggs hatch in a few days and the larvae feed on the carcass until nothing is left but important nutrient elements. These nutrients are then stored in the soil until they are taken into the roots of plants. In addition to cleaning up rotting debris, these insects help recycle nutrient elements.
#4- Soil Tillage: The tiny black mound ant burrow out elaborate tunnels in the soil which lead to open spaces where ants live in a colony. This colony includes a queen ant, and worker ants who attend to the larvae. The mound ants and all other soil burrowing insects help keep the soil loose enough to absorb air and water.

7. Give the students the following descriptions. Have them designate which jobs these insects provide, numbered 1-4. You may wish to augment these descriptions with pictures of the animals.
flesh fly: This black fly has gray markings. Its larva feeds on decaying vegetation and dead animal parts. The adult feeds on the nectar of plant flowers.
robber fly: This brown fly is a fierce predator. It can capture another insect on the wing, drop to the ground, and suck the prey dry in a matter of seconds. The larva of the robber fly is also a predator, feeding on tiny insects in the soil.
least skipper caterpillar: This caterpillar slowly works its way up and down grasses munching on the tender shoots as it grows.
least skipper butterfly: This golden brown butterfly slips nectar from flowers and also eats decaying plant materials lying in the prairie soil.
painted lady butterfly: This beautiful butterfly visits the flowers of prairie forbs in search of nectar.
spotted cucumber beetle: The larva of this beetle feeds on the dead roots of grasses and forbs. The adult feeds on the leaves and flowers of forbs.
digger wasp: The adult wasp feeds on the nectar of flowers. The female adult burrows into the soil in search of beetle larvae, sometimes tunneling a few feet deep. Upon finding a beetle larva, it stings it and then digs a tiny cell around the body. The adult then lays one egg on the back of the larva. When the wasp larva emerges, it feeds on the body of the beetle larva.
aphids: This insect sucks the juices of plant stems and leaves. The aphid discharges a clear, watery liquid, called honeydew. Ants feed on honeydew.
praying mantis: This insect preys upon grasshoppers, crickets, bees, caterpillars, and flies. The nymph also preys upon other animals, including plant lice.
tumblebug: The male and female roll a ball of animal dung across the prairie floor. After the dung is pressed and round, the adults dig a tunnel in the soil and drag the ball of dung into it. The female then lays an egg on the dung. The larva hatches later and feeds on the dung until it develops into an adult.

Introduce Scientific Principle/Environmental Issue

8. Insects exist on the prairie in many forms. They all begin as immature nymphs or larva. Nymphs look like smaller versions of their parents until they undergo a series of molts to reach their adult size-incomplete metamorphosis. Larvae look nothing like their parents. They molt but then rest as a pupa, often in a cocoon, until they emerge as an adult-metamorphosis. The prairie ecosystem could not exist without the important work insects do. They pollinate, decompose dead plant material, till and aerate the soil. The plant life and balance of the entire prairie ecosystem works mainly due to insect participation.

Relate Activity and Concept

9. Review the insects listed above. Have the students indicate which of the insects have incomplete and complete metamorphosis.
10. Can students think of any animals that they encounter in their home ecosystem (city, rural, etc.) and what comparable jobs they do?