Setup time for the laboratory is 2-3 hours and consists mainly of making solutions. The laboratory exercise itself works best with a 3-hour block of time, although it can be done in 2 hours if the lecture is done separately. When the exercise is done as an investigative project, students repeat the project three successive weeks. This allows extra time for them to make their own solutions and to run replicate experiments for statistical analysis. We have used both crickets and roaches successfully for this experiment.
Students are less squeamish about handling crickets.
Roaches have a large amount of fat body in the abdomen that must be removed during the dissection, and this slows down the experiment when students are running duplicates. The transporting tubules of excretory systems are remarkably similar in animals as diverse as insects and mammals. The Malpighian tubules of insects are finger-like extensions of the intestinal tract, located at the junction of the midgut and hindgut. Excretion is achieved exclusively by secretion of ions and organic molecules from the hemolymph into the lumen of the tubule. This is unlike the mammalian kidney, where most of the contents of the kidney tubule derive from plasma filtered into the lumen at Bowman's capsule.