Preparing for DE Internal Anatomy Lab  

1. The Insect

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.  The much smaller, house-dwelling cockroaches will be difficult to dissect, so it is best to try to catch a large outdoor-dwelling roach.


2. Trapping a Cockroach

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 slice 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.

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

If you do not already have a pre-made dish, a slab of paraffin (candle wax) 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 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. Kill Your Roach

Just before conducting your dissection, kill your roach using a killing jar as you normally would.  Then follow the directions on the main Internal Anatomy Lab page