HandsOn 19 - Termite Tunnel Patterns
The process of finding wild termites (as opposed to domesticated termites) varies by geographic region. In New England, we go to a wooded park and search among the remains of dead trees on the ground. Termites like soft, damp wood. An ax, a hammer with a good claw, or a crowbar are useful tools to pry or split open rotting wood. You will encounter many different insects during your search, in particular carpenter ants, but with luck you will find termites. The best time to find termites is during warm weather. In the fall termites go underground to escape the cold winter. (What can be so fine as a day in June hunting termites with your hatchet?) In some cases it is possible to order termites from biological supply companies. The termites we find locally are the species flavipes reticulitermes.
Once a colony is found, collect the pieces of wood and place them in plastic trash bags. If possible, also collect some of the earth surrounding the piece of wood. It is a good idea to use a double bag (one bag inside another) to prevent tears and the subsequent escape of the termites.
When you get the termites back to the laboratory, place the logs in plastic trays, boxes, or tubs lined on the bottom with the dirt you collected. Be sure to drill or puncture holes in the lid of the container for ventilation. Periodically the wood should be sprayed with water to maintain an adequate moisture level. The greatest threat to the colony is dehydration. If you plan on keeping the termites for a period of time, use a mold inhibitor in the spray. This will prevent mold from growing on the wood, which can kill the colony.
To create termite tunnels in the laboratory, follow this procedure:
2. Moisten a cotton ball with acetone and lightly wipe the inner surface of the cell. Allow a few minutes for evaporation. This will remove fingerprints and any microorganisms remaining on cell.
3. Fill a beaker or other container with sand, and slowly sift the sand over the bottom of the cell until the surface is evenly covered. Level the sand with the shim around the outer edges. This can be accomplished by using your top acrylic plate as a straight edge to smooth out the sand. Hold the top sheet perpendicular to the cell and slowly drag it across the surface. You will know when the sand is flat because very little sand will be displaced as the plate is dragged along the cell.
4. Moisten the sand with water using a spray bottle. The sand should be wet, but not so wet that pools of water accumulate on the sand. About 1 fl oz. of water is the right amount.
5. Secure the top of the cell to the bottom using by placing bolts in each of the holes that you drilled. Tighten down the bolts with the wings nuts. Be careful not to disrupt the smoothness of the sand.
6. Place tape along the entire side of the cell where the top and bottom plates meet.
7. In the center of the bottom plate of a small petri dish, drill a hole the diameter of the hole on the top plate of the termite cell. This would be 1/2" if you strictly followed the instructions above. Tape this bottom portion of the petri dish onto the top plate of the cell with its hole coincident with the cell's hole.
8. Inserting Termites into the Cell: When handling the termites, do not expose the termites to excessive light, heat, or air for any significant length of time. This is particularly important if you decide to use an overhead projector to display the pattern that forms. This works, but remember that dehydration is a threat to the survival of the termites and overhead projectors produce a large amount of heat.
b. Occasionally, pieces of wood will end up in the petri dish. Make sure that the pieces are removed before proceeding.
c. Pour the termites into petri dish taped to cell and cover this petri dish. When most of the termites have entered the cell, you can push the stragglers over the edge and remove the petri dish.
10. After about a day, most of the termites have descended into the damp sand. Kick the stragglers over the edge, remove the petri dish, and cover with tape.
11. It takes one to three days for the pattern to develop. Take frequent pictures at regular intervals. If possible, use a video camera to grab images. Alternatively, trace the developing pattern as a function of time on a piece of paper, or scan the pattern into the computer. In any case, keep records of the overall radius of the growing pattern as a function of time.
12. Watch the termites carefully. Termite society is divided into different classes or castes. Can you distinguish the different castes and the tasks each caste carries out? How do they communicate? How do they make the tunnels? Do their tunnels intersect with one another? What keeps the sand from collapsing into the tunnels? Do you see any preferred directions to their activity? If so, can you reason why they have selected these directions?
2. The sand should still be sufficiently moist to be able to incline the bottom plate without the sand running off. If you incline the bottom plate vertically, the termites will fall out of the cell. Do this over the wood/dirt where you maintain your colony of termites. The few termites remaining can be removed with forceps.
3. After the termites in the bottom plate are removed, remove the termites on the top plate.
4. Clean the bottom and top plates. Before using the plates again, let them dry for 24 hours. The plastic plates absorb moisture from the sand, and warp slightly when they are separated. The plastic must be allowed to thoroughly dry.
2. Is the pattern random? the product of a diffusion process? Are the termites effectively ballistic-do they move along a single straight line? Is it necessary for them to search every place in the cell?
3. Suppose the termites move like randomly-walking molecules. If the average radius of the foraging pattern grows to ten centimeters in one day, how long would you expect it to take for the pattern to grow to a radius of 20 centimeters? Twice as long? Four times as long? Do your observations match your prediction?
4. Using your scanned or video-captured images, measure the fractal dimension of the pattern at different times. Follow the same steps you used in Unit 3 by first turning your image into an digital image file and then find the dimension with the Fractal Dimension program.