Introduction

Table of Contents


hy Study Wasps?

Animal Behavior is a complex subject. Each species has its own intrinsic behavior and social structure. Individuals may display different behaviors. Synthesis and interpretation of these actions and structures can be tedious without prior knowledge of possible models of behaviors.

Paper wasps of the genus Polistes (Hymenoptera: Vespidae) provide us with such a model. Like many eusocial insects, Polistine wasps have been extensively studied for several reasons. First, because of their short life spans, they are easy to breed and can be studied over several generations, facilitating studies of kin selection. As well, patterned behavior of the social insects can be easily diagrammed and used to study tensions between cooperation and conflict. Furthermore, genetic testing can be easily conducted on social insects because they can be destroyed, collected, measured, and dissected, while ethical and ecological concerns restrict such experimentation on vertebrate species. Such extensive genetic and behavioral studies have led to the development of extensive kin selection and kin recognition theory.

The colony structure and behavior of Polistes further benefits behavioral studies. While many eusocial insects inhabit only narrow geographical regions, species of Polistes inhabit an extensive area in various geographical regions and climates. Polistes build nests under the eaves of homes in urban areas, in barns and other protective structures in rural areas, and on twigs of bushes in the wild. Their open nests, lacking a protective envelope, allow for easy observation and recording of the caring and development of the larva and of the behavior of the colony as a whole.

olistine Wasps

Colonies of Polistine wasps are composed primarily of females; males are produced only for mating purposes. Colonies include queens, the principal egg layer in the colony, gynes, females that will become a queen in the following year, foundresses, mated females capable of laying eggs in a spring nest, and workers, females who work on their natal nest and have the potential to become queen. A female wasps role is not predetermined; when a females emerges from her cocoon, she has the potneial to become a queen or a worker. Her final role in the colony depends on the status of the colony cycle and on a number of other social factors.

he Colony Cycle

Colonies are started in the spring by mated, overwintered females that emerge from their hibernation sites on warm days. While single females sometimes start a colony, often times a group of females will found a colony together. This group of females must fight amongst themselves to establish a dominance hierarchy. The female at the top of the hierarchy becomes the queen, while the rest of the foundresses start to function as workers. The ovaries of the queen become well developed and she turns into the main egg layer. The ovaries of the rest of the foundresses start to decrease in size as they take on the dangerous tasks of foraging for water, for plant fibers to construct the nest, and for nectar and caterpillars to feed the queens and her offspring.

The foundress or foundresses raise a generation of offspring, which, upon emerging as adults, become workers. If there is enough time before the end of the season, the workers help raise more workers. If not, they will help raise a generation of females that will mate and hibernate to become foundresses the next spring. A generation of males is also produced by the end of the year. They will mate with the future foundress and, along with the workers, will die over the course of the winter.

eviations from the Colony Cycle

The shortness of the growing season of northern climates leaves little room for deviation from the general colony cycle. However, in populations with extended growing seasons, it is more likely for the structure of the colony to change over the course of the season. Drastic changes may result from the destruction of the nest by predators such as raccoons or birds. Ants frequently raid nests and take all the brood for food. As well, parasites often infest the larvae and pupae causing irreparable damage to the brood. These factors often make it difficult for colonies to reach the end of the nesting cycle to produce the future reproductives, and cooperative work becomes an essential factor in recuperating from such events.

Outside factors, such as parasites and predators, have an extensive effect on a colony. However, drastic changes to the hierarchic structure of the colony may result from conflicts of interest within the colony itself. For example, when the queen dies, one of the co-foundresses or one of the workers takes over the queen's position. Due to the varying genetic relatedness of the different females, the takeover leads to a conflict of interest between workers and foundresses. Part of this project will be to determine who you believe will take over.

n Introduction to the Project

The Social Behavior of Polistine Wasps Project is based on data collected on three nests located in Texas' Brazos Bend State Park with the permission of Texas Parks and Wildlife (Permit 36-93) in May 1994. The nests of Polistes bellicosus were videotaped over a four day period shortly after worker emergence. Before videotaping the nests, nearly every wasp was marked using spots of various colors of paint in order to distinguish individuals. In the first half of the videotaping period, nests were left undisturbed. After three days, the queen was removed and the nests were again videotaped.

After collecting the behavioral videotape, all wasps still on the nest were collected (missing wasps died between video and collection). Each of the marked wasps was assigned a number, photographed, and later dissected. Before dissection, the head size of each of the wasps was measured. Upon dissection, the ovaries of each of the wasps were removed and photographed. Following dissection, microsatellites were used to determine maternity and genetic relatedness.

In the following project, you will be expected to utilize components of all of the collected data in order to determine the social structure of the colony, the importance of variation amongthe wasps, and, if you have the videotapes of the nest, the effect of the social structure on individual behavior. Throughout the project, you should attempt to make connections between the various data. Scientists must continuously interpret data and be able to make connections between the results of different data, projects, and experiments. Once they make these connections, they are then expected to be able to coherently and precisely present their results. As science researchers, you should look at the questions as a stimulus for conducting your own research based on the data provided.


ssignments

Below, you will see three different projects which students have participated in over the last year. The first assignment, presented in two parts, was the original project used by Professor Joan Strassmann in her Animal Behavior (Bios321) class at Rice University. The project was a culmination of the ideas covered in class throughout the 1994 fall semester. The project emphasizes a student's ability to work in a group to develop a method of synthesizing and presenting collected data.

The second assignment, presented to eleventh and twelfth graders at the South Texas Science Academy in Mercedes, Texas, focuses on developing observation and analysis skills. Students were asked to select three questions which they wished to explore. This choice encouraged them to individually chose the research path they would follow and to focus on a particular problem, giving them a sense of responsibility for the ultimate outcome of the project.

The third set of questions were given to fifth graders participating in Take Your Daughters to Work Day at Rice University. The questions are designed to develop observation skills.


Rice University Animal Behavior (Bios321)
Paper Wasps as a Model System: First Assignment

Three colonies of Polistes bellicosus were videotaped in the wild at Brazos Bend State Park for a number of hours. After videotaping, the colonies were collected and the females were measured and genotyped. These videotapes are available from the reserve desk in the library. I also put one set of videotapes in the biosciences computer classroom, where several VCRs are available. These data are available to you over owlnet in a Mosaic format in the form of images of the heads (an indicator of size), the ovaries (an indicator of reproductive status) and DNA microsatellites (used to partition reproduction among females and to assess genetic relatedness). This assignment is based on your analysis and interpretation of these data.


1. What do Polistes bellicosus females do? Make a complete list of all the behaviors you see performed. This list should be organized by general type of behavior and should have a brief name followed by a longer description. Give a specific place on a tape which you feel is a good example of the behavior. (5 points)


Partial example (from mockingbirds):


2. How do Polistes bellicosus females partition their efforts between reproducing and caring for young? Why? Support your view with appropriate behavioral, ovarian, size or genetic data. You may cite specific locations on the tapes. You may illustrate your answer with figures, tables and graphs. (5 points)


3. How is reproduction divided up in the group of Polistes bellicosus females? Why? Support your view with appropriate behavioral, ovarian, size, or genetic data. You may illustrate your answer with figures, tables and graphs. (5 points)


4. If the dominant female is removed who would the foundresses prefer to have assume the role of dominant female? If the dominant female is removed who would the workers prefer to have assume the role of dominant female? Why? Support your view with appropriate behavioral, ovarian, size or genetic data. You may illustrate your answer with figures, tables and graphs. (5 points)


5. Who do you think will actually take over? Why? In whose interests is this? Support your view with appropriate behavioral, ovarian, size or genetic data. You may illustrate your answer with figures, tables and graphs. (5 points)


Honor code: You are strongly encouraged to work in groups on many aspects of this assignment. You may watch videos, look at data and brainstorm together. You can develop a list of behaviors together. You may generate figures, tables and graphs as a group, or share them within a group only if you have participated in the data analysis that supports each figure, table or graph. Clearly label which figures, tables or graphs you did independently, and which you got from the group. Write a few sentences describing to me how your group worked. Sign the honor code on this assignment. The final text of the report must be done independently!


Paper Wasps as a Model System: Second Assignment
Subsequent to the recordings you have already seen of Polistes bellicosus, we removed a dominant female from each of the three colonies and again recorded behaviors. These tapes are available in the library. This assignment is based on these videotapes, the comments on your previous assignment, and on your reading for this class.


1. How does the behavior of Polistes bellicosus change after the removal of a dominant female? Are females more or less active? Is there more or less aggression? Is the dominance hierarchy more or less well defined? Is there more or less foraging for food? Do other behaviors associated with bearing or caring change? Are there great differences among the colonies, and why or why not?


2. Who becomes the new dominant female? How can you tell? In whose interests is this? Were your predictions supported? Why or why not? Take into account any comments your instructors made on the first assignment, if this is appropriate.


3. A model system in biology is a system in which important conceptual issues can be tested and the results generalized to other systems. A model system is usually particularly amenable to the study of an important general phenomenon. This might be the case because it involves an animal with short lifespans, or that is easily reared, observed or experimented on, or because it has been thoroughly studied previously. A model system should be simple and general enough that important concepts can be easily explored and understood. This project has used Polistes bellicosus as a model system for kin selection. What are its strengths and weaknesses as a model system? In answering consider similarities and differences of kin selection in wasps and other animals where kin selection has been studied, such as other social insects, dwarf mongooses, naked mole rats, Florida scrub jays, or other animals from your class reading.


Honor code: You are strongly encouraged to work in groups on many aspects of this assignment. You may watch videos, look at data and brainstorm together. You can develop a list of behaviors together. You may generate figures, tables and graphs as a group, or share them within a group only if you have participated in the data analysis that supports each figure, table or graph. Clearly label which figures, tables or graphs you did independently, and which you got from the group. Write a few sentences describing to me how your group worked. Sign the honor code on this assignment. The final text of the report must be done independently!


South Texas Science Academy
Exploring Social Wasp Behavior


I. Questions based only on videotapes of behavior.

  1. What do wasps do?
  2. Do some wasps perform certain tasks more often than others?
  3. Does the behavior of the foundresses who are mated and have survived the winter differ from the behavior of their daughters who are young and have not mated?
  4. How do the wasps build and care for their nest?
  5. How do the wasps feed their young?
  6. How do the wasps protect their young?
  7. How do the wasps clean themselves?
  8. How do the wasps interact among themselves?
  9. How is the behavior of wasps similar or different among the three colonies?
  10. Do wasps on the larger colony bring in more food in all than the smaller colony, or does each wasp on the larger colony simply work less hard?

II. Questions based only on material available at the website.
  1. Do foundresses and daughters differ in size or degree of ovarian development? Is this the same for the three colonies? How do you compare ovarian development among wasps?
  2. Which foundress has produced most of the daughters? Is there only one queen on all three colonies? Use both microsatellites and ovaries to answer this question.
  3. Is the main queen larger than the other foundresses in these three colonies? If not why do you think she is queen anyway?
  4. There is one wasp on one nest that could not have been the daughter of any of the females. She was probably a worker that got lost and joined the wrong colony. Which one is she?
  5. In wasps, sisters share three quarters of their genes on average. Are the foundresses on the same colony likely to be sisters? Are the daughters on the same colony likely to be sisters? Justify your answer.

III. Questions based on website material and videotapes.
  1. Does the main egg layer behave differently from the other foundresses? Justify your answer.
  2. Does the wasp who is not related to the others on the nest behave differently from the daughters that were born there? Justify your answer.
  3. Do daughters with some ovarian development behave differently from daughters with no ovarian development? Does your answer vary depending on the nest? Justify your answer.
  4. Does the largest daughter behave differently from the smallest daughter? Does your answer vary depending on the nest? Justify your answer.
  5. Does the largest foundress behave differently from the smallest foundress? Does your answer vary depending on the nest? Justify your answer.
  6. If the main egg layer were removed who do you think would take over? Justify your answer.


BRING OUR DAUGHTERS TO WORK ON WASPS
Electronic Studio Project


  1. What do wasps do on their nest?
  2. Does the largest female have the largest ovaries?
  3. Who is the queen?
  4. Does the queen act differently from the other females?
  5. Who is unrelated to the egg layers on the nest?
  6. Does the unrelated female behave differently from the other females?
  7. What else can you figure out about these wasps?



[Home Page] [Introduction] [Assignment] [Behavior]

[Head Size] [Ovaries] [DNA Microsatellites] [Relatedness]



© Joan E. Strassmann, reproduction by permission only
updated 4 April 1996, strassm@rice.edu