In this lab you will dissect a freshly killed cockroach and learn to recognize various internal organs and organ systems.
The main objectives of this lab are to help you:
- distinguish among different types of tissues within an insect's body
- learn the location and appearance of internal organs in a typical insect
You will need the following materials for this lab:
- Lab handout (PDF)
- Large, wide-mouth jar
- Fresh bread (one slice)
- Beer (several drops)
- Paper towel or construction paper
- Petroleum jelly (i.e. Vaseline
- Nail polish remover – acetone
- Insect pins
- Dissecting scissors
- Fine-point forceps
- Dissecting dish or tray
- Candle wax or paraffin
- Stereomicroscope or hand lens
|The American cockroach, Periplaneta americana, is a relatively large, cosmopolitan insect that will serve to illustrate the appearance and arrangement of internal organs in a typical insect. Most of the structures described in this lab will be best viewed with the aid of a stereomicroscope or a hand lens. A good dissection requires time and patience -- make small cuts and don't remove a piece of tissue unless you know what it is.|
1. Make a cockroach trap
Fasten a paper towel or a piece of construction paper around the outside of a wide-mouth glass jar. The paper should extend from the base of the jar to near its lip so a cockroach can climb up the outside. Put a slide of fresh bread into the jar and add a few drops of beer to make a yeasty-smelling bait. Smear petroleum jelly liberally around the inner lip of the jar.
2. Catch a cockroach
Leave your trap overnight in an area where you think cockroaches may be active. Basements of apartment houses, farm buildings where animals are kept, outhouses, or vents to sewer lines or septic systems are good prospects. Look for adult cockroaches (ones with fully developed wings) in your trap the next morning.
3. Make a dissecting dish
A slab of paraffin in a shallow bowl or tray will serve as an acceptable dissecting dish. If possible, use a dark-colored container, apply black spray paint, or make a plastic liner from a black trash bag. Most internal structures are white or translucent so they show up best against a dark background. Alternatively, you may wish to melt the paraffin (or candle wax) in a double boiler and pour the liquified wax into a shallow bowl or tray. In any case, leave at least 3/4 inch of space between the top of the wax and the top of the container. You will need enough room to completely cover your cockroach with water during the dissection.
4. Perform your dissection
Use a few drops of nail polish remover (acetone) to kill the cockroach and then follow the directions printed in your lab handout. You may also view an Audio Slide Show that takes you step by step through a typical dissection. Still images from the slide show can be viewed separately in the Roach Guts picture gallery.