Ant Wars!

Middle School Math & Science Collaborative

Paul C. Johnson
Department of Natural Resources
University of New Hampshire
Durham, NH 03824


Social insects such as ants use the direct transfer of behavioral chemicals to regulate many aspects of colony life. When ants meet, they will regurgitate a small amount of their gut contents and exchange it with the other ant. This is called trophallaxis. In some ant species, a behavioral chemical identifies the members of an ant colony as nest mates. In others, the type of food exchanged identifies members of the colony (you are what you eat!). When meeting a member of another nest, battle may occur; this reduces competition for resources in the area. The pavement ant, Tetramorium caespitum L. (Hymenoptera: Formicidae) is a common ant species. It lives in cracks in the pavement of sidewalks and roads, and incidentally in the cracks in basement floors (a good source of ants even in winter). It conducts fierce battles with other colonies. We have collected ants from two colonies of pavement ants. We have also collected from a colony of pharaoh ants, Monomorium pharaonis (L.) (Hymenoptera: Formicidae). Any other combination of ant species will do, but these are common household pest and relatively easy to find, even in winter. In this lab we will examine what happens when ants from different colonies meet.

Materials

1 stereozoom microscope.
3 petri dishes with 10 ants each.
1 data sheet per group.
1 stopwatch per group (optional).

Procedures

Each lab group will be given five ants each from colonies of the two species in covered petri dishes, and ten ants from the other pavement ant colony in another dish. This dish serves as a "control" (who knows...maybe they just like to fight!). Observe the ants in each dish under your microscope. Do they fight? If they do, how would you describe the action? Learn to recognize each species; it helps to give them a name of your own design! Begin recording data on the behavior of the ants by having each member of the group observe the control dish (i.e. the one with ten pavement ants) for 30 seconds. Members of the group should time the other members by using the stopwatch provided (or by counting slowly to 30). Record the number of ants observed fighting on the group data sheet provided under the CONTROL column. [Note: Record the number of ants fighting, not the number of fights, since some fights may involve more than two ants.]

Next, take five of the pavement ants from the control dish and place them in the pharaoh ant dish (this in an interspecific meeting, i.e. between different species). Place the remaining five pavement ants from the control dish into the other pavement ant dish (an intraspecific meeting, i.e. within the same species). Observe the activity of the ants in each dish. Do they fight? Again, how would you describe the action? Take turns observing the ants in each dish for a 30 second period. Record the number of ants engaged in fights during your 30 second observation on the group data sheet provided. Be careful to record your observation under the appropriate column, either INTERSPECIFIC or INTRASPECIFIC.

GROUP RESULTS

Report your results to your instructor who will prepare a "scattergram" of your data on the computer. While waiting to report, you may continue to observe the ants, but don't change your data! Once we have all the data recorded, the groups should put away the microscope and ants. The next problem is to devise a way to consolidate the data within each group and compare the behavior of the ants when confronted with members of their own colony (CONTROL), another colony of the same species (INTRASPECIFIC), and ants of another species (INTERSPECIFIC).


FOOD FOR THOUGHT

If a different number of ants were used by some of the groups, could your group's measure be used to compare results between groups?

OPTIONAL ANALYSIS

One of the things that students will probably note as they record the data is that some individuals and groups see very few fights, even in the interspecies meetings, while others seem to see fights everywhere they look. This is normal since this type of data tends to fit a normal distribution.

If you have enough students (about 20 minimum), and the students seem ready for it, try plotting the data from the interspecific meetings as a frequency distribution. To do this, plot the number of students observing 0, 1, 2...8, 9, and 10 ants fighting during their interspecific observation on the graph provided. This can be easily done with a show of hands...i.e. ask,"How many observed zero ants fighting?" Plot the number of students responding above zero on the x-axis; repeat for two fighting, three fighting, etc. [Note: the number of students observing one ant fighting will be zero, since an ant can not fight with itself.]

With enough data points, you should end up with a bell shaped histogram, with most students clustered around the mean number of ants fighting, and relatively few at either extreme. You can use this exercise to explain the importance of repeated observations and the use of averages to describe data. With advanced classes, you might introduce the concept of variance and standard deviation as a measure of variability around the mean.

Variance

The variance is the most basic measure of variability. It is the average of the squared deviations from the mean. To compute it, you first compute the mean number of fights (from the table above), then subtract the mean from each of the student observations, square each result, add them up, and divide by the number of observations.

Standard Deviation

The standard deviation is the most frequently used measure of variability. To compute the standard
deviation, simply take the square root of the variance. One of the questions you will undoubtedly get is, "why do we have to square the deviations?" Have the students try computing the average of the deviations without squaring them first. It will invariably sum to zero since the mean is by definition the mid point of all the observations. Deviations above and below the means cancel each other out.

VARIATIONS ON THE THEME

The most valuable variation on this lab will probably be the elimination of the interspecific comparison. This make the collection of the ants much easier, and still provides the basic comparison between colonies (in this case colonies of the same species). This will work for most ant species, but not all species. for example, the pharaoh ant is notoriously nonagressive toward other colonies of pharaoh ants. This variation also allows the lab to be performed in less time.

An interesting variation of the experiment would involve repeated collections of pavement ants over several days from two competing colonies. Set up petri dishes pairing the two colonies by day. Since colony recognition relies on exchange of behavioral chemicals provided by the queen or differences in food being exchanged, ants removed from the influence of the queen for several days and fed on the same food material should not display aggression toward the other colonies. You could even design experiment that tested whether nestmate recognition was behavioral chemical based or food based by replicating the experiment described above, but providing each colony with different food supplies. If aggression was retained in combinations fed on different foods, but lost when fed on the same foods, chances are it is food based nestmate recognition.

Some of these variations on the basic experiment may be too complex for use in a class situation, but might make excellent science fair projects for some students.

INTEGRATION OF SOCIAL STUDIES AND ART

One of the most controversial areas of study in biology today is sociobiology, the objective study of social interactions from a biological basis. Sociobiology is an extension of the "Nature vs. Nurture" debate, reinvigorated by the work of E. O. Wilson in the mid-1970's. It attempts to answer questions about the nature of social interactions (including human social interaction) by applying basic biological principals. Since Wilson is an entomologist who specializes in ants, it would be very appropriate to extend this exercise into the social studies class. As background, Fisher (1991) gives an excellent overview of sociobiology, its origins, and the nature of the comnflict it has engendered. It should provide enough information on sociobiology to suggest an appropriate curriculum.

With regard to art, ants are frequently used in works of art. For example, M. C. Escher's famous wood block print, Mobius Strip II (Red Ants), provides an opportunity to explore math concepts (e.g. topology) in an artistic format. Another possibility would be to have students construct anatomically correct works of art focusing on the ant, or other appropriate insects. Scientific illustration is an exacting and fascinating field of art that is often overlooked in our art curriculum.


SIMANT

If you have the computer available, the program SimAnt provides an excellent simulation of ant battles for territory. It integrates some neat graphs and a excellent database of ant facts. It was inspired by Bert Holldobler and Ed Wilson's (1990) Pulitzer Prize winning book, The Ants. The attached exercise might be an good adjunct to this lab.

Mission Impossible?

Good Morning, Jim. We have recently learned that a colony of red ants has invaded the territory of a black ant queen friendly to our government. With the assistance of an excellent simulation of ant life, SimAnt, you can become a "leader ant" in the colony of black ants. Your mission, should you choose to accept it, is to lead the colony in an all out effort to eliminate the red menace that shares your habitat. To do this successfully, you will have to think like an ant and utilize all of your instinctive abilities. You have at your disposal legions of sister ants (assuming you can convince your queen to produce them, and you keep her well fed), alarm and trail marking pheromones, and an unlimited number of lives in which to accomplish your goal. As always, should you or any of your IM force be caught or killed, the Secretary will disavow any knowledge of your actions. . .this lab handout will self-destruct in five seconds.

Procedure

Sign up for a block of time on the computer. About one hour should be plenty of time.


INSTRUCTOR'S NOTES

We would anticipate that the pavement ants will fight with the ants of a different species (interspecific), and will probably fight with members of another pavement ant colony (intraspecific), but will not fight with members of their own colony (control). If you reverse the experimental design and test pharaoh ants with members of another pharaoh ant colony, they probably will not fight. This is related to the way in which they produce new colonies. . .by budding. That is, a group of worker ants will pick up some of the brood and move to a new location, raising a new queen from the brood. In a sense, pharaoh ant colonies in the same general area are kind of a super colony. On the other hand, pavement ants are notoriously aggressive, waging massive battles with any competing colony regardless of species. Again, you may use any combination of species within the experimental design, but (as noted for pharaoh ants above) the results depend on the species involved.

There are at least three valid measures describing group results: the average number of ants fighting, the total number of ants fighting, and the percentage of ants fighting. There are likely to be others that are not so obvious! You will have to judge their validity on a case-by-case basis. Try to have the students determine if their measure can be used to compare groups of data based on unequal numbers of ants, and why.

Generally speaking, the total can be used to compare observations between groups with the same number of observers and the same number of ants. If the number of observers is different between groups, the total will not work, and the average becomes the proper statistic for comparisons. Finally, if the number of ants in the experiment varies between groups (e.g., some petri dishes have only eight or nine ants. . .some do escape occasionally), then the percentage of ants fighting is more appropriate.


References

Fisher, A. 1991. A new syntehsis comes of age. Mosaic 22 (Spring):2-17.

Holldobler, B; Wilson, E. O. 1990. The Ants. Harvard Univ. Press: Cambridge, MA. 732 pp.



Ant Wars Data Sheet

Group Member

Control

Intercolony

Interspecific

1
2
3
4
5
6
7
Group Result

The formatting of this table may not work on all web browsers.


For information
Paul C. Johnson
Department of Natural Resources
258 Spaulding Life Sciences Building
University of New Hampshire
Durham, NH 03824
Phone: (603) 862-1717
FAX: (603) 862-1713
e-Mail: pcj@christa.unh.edu


Last modified on August 18, 1997