Biological experiments involving animals in K–12 classrooms can be time consuming or logistically difficult. Insects are small and easy to obtain, making them suitable for classroom use. We provide an experiment using insects that will teach students how to use the scientific method to formulate and test a hypothesis. The experiment is based on a case study involving an insect used as a biological control agent that targets an invasive weed, and the rigor of the experiment can easily be tailored to different grade levels. Using ~1 m2 arenas set up in the classroom, students measure insect jumping or walking distances as a proxy for dispersal capabilities in the field, and more advanced classes can investigate variables that affect jumping or walking distance and direction.

Introduction

Integrating components of research into the classroom provides students an opportunity to practice testing their own hypotheses by following standardized procedures, collecting and analyzing data, and discussing outcomes. While an entire research project can require an unrealistic time commitment for the average science class (National Research Council, 2006), a research-type experiment can be conducted within a class period. One way to do this is to use entomological research experiments, which are well suited to K–12 classroom environments (Sauer, 1976; Matthews et al., 1997; Miller, 2004). Haseman (1923) wrote that insects “are present everywhere, in all seasons and are known to every child of the city or farm. They are easily observed in the field and can be kept in confinement for study.” Many species of insects are easily obtainable through biological supply companies or pet stores, and many more can be found and captured on campus by students, making entomology a cost-effective discipline through which students can be introduced to animal behavior and ecological concepts, as well as research methodology. Additionally, protocol approval from an institutional animal care and use committee (IACUC) is not needed for work with insects.

This article is based on an activity originally developed as a hands-on experiment for students who were participating in a two-week-long STEM (Science, Technology, Engineering, and Mathematics) summer camp program called CSI:STEM, run by the Broward County Crime Commission, Broward County, Florida. The students were 9–16 years old, but the majority were middle school students. The objective of the experiment was to determine the individual dispersal capabilities of an insect used as a biological control agent of an invasive plant.

Background on the Biological Control of Invasive Weeds

In southern Florida, invasive species affect all native habitats (Ewel, 1986; for additional resources on invasive species, see the National Invasive Species Information Center website at https://www.invasivespeciesinfo.gov/). Some of these species have established populations on a scale where eradication is not a possibility and the only course of action is management of their population (Harvey & Mazzotti, 2014). Invasive plant species are primarily managed by herbicide application (UF/IFAS Center for Aquatic and Invasive Plants, 2018), but another way that scientists are attempting to further control these plant populations is through the use of biological control agents, such as insects, that control these invasive species in their native range. Researchers scour the native range of an invasive plant (i.e., target) looking for insects feeding on it. The candidate insect agents are brought into the lab and tested for feeding and reproduction on the target, native plants genetically related to the target that occur in the invaded habitat, and economically important crops in the invaded habitat to determine the agent's host range and specificity. Once these insect agents have been deemed safe by rigorous scientific testing and vetted through an extensive permitting process, they are released into areas where their invasive host plant occurs. Ideally, the insects establish breeding populations and begin dispersing to new areas with host plants without much further human intervention (McFadyen, 1998). Further research is still necessary to determine how effective the agents are at controlling the target, if they are persisting in the habitat, and if they are dispersing to new areas (for examples of research on biological control agents, see the USDA Invasive Plant Research Laboratory website at https://www.ars.usda.gov/southeast-area/fort-lauderdale-fl/iprl/). Dispersal is often the most difficult aspect of agent efficacy to study, as most of the plant biocontrol agents are small insects.

Research is currently underway to assess the dispersal behavior of the biological control agent Megamelus scutellaris (Hemiptera: Delphacidae). This planthopper feeds exclusively on common water hyacinth (Eichhornia crassipes), an invasive, floating aquatic plant in Florida. Water hyacinth was introduced to Florida in the late 1880s (Gordon & Thomas, 1997) and is one of the most invasive plants in the world. It can double in biomass every two weeks (Reddy & DeBusk, 1984), quickly clogging waterways, pushing out native plants, and altering water chemistry (Penfound & Earle, 1948). Megamelus scutellaris feeding reduces water hyacinth's growth and reproduction (Tipping et al., 2011). This small insect (<5 mm) was initially released in 2010, and monitoring shows that it now has spread from release sites (Tipping et al., 2014; Moran et al., 2016). Dispersal is an integral part of this species' behavior because it lives in an ephemeral habitat (Denno et al., 1991) where seasonal variation, anthropogenic control of water level, and herbicidal management affect its host plant's distribution. When conditions become unfavorable, M. scutellaris needs to be able to disperse to new areas. An important piece of information when determining dispersal is knowing how far an insect can move after being released. To estimate this initial dispersal, this experiment required students to measure the distance and number of times a planthopper can jump before it becomes fatigued.

While this experiment was initially conducted on M. scutellaris, the methods can be altered to easily accommodate other jumping insects like crickets or grasshoppers, or to accommodate walking insects collected outside. It can also be adjusted to the educational level of the student group. In the basic experiment, groups of students follow standardized procedures, record and analyze their data, and then discuss reasons for variations between insect types (if using different types), individual insects, and student groups. The advanced experiment is modified to include student-driven inquiry of insect behavior. For older students, more advanced classes, or longer/multiple class periods, this would incorporate using the scientific method to develop and test hypotheses explaining insect dispersal.

Learning Objectives

  • After completing the basic activity, students should be able to demonstrate a general understanding of the scientific method.

  • After completing the advanced activity, students should be familiar with the scientific method and be able to link observations to hypotheses and predictions, plan and execute a simple experiment, collect data, and analyze and discuss their findings.

Experimental Setup

The goal of the experiment is to measure the distance an insect moves (Table 1). Students can accomplish this by releasing an insect onto a large sheet of paper (i.e., arena) and marking and measuring its movements. Insects can be gently encouraged to jump or move with a small paintbrush, a cotton-tipped applicator, or even the eraser end of a pencil. Students should work in pairs or groups in which one student observes the insect and the other stimulates the insect to jump or move. After completing this basic experiment, students should be encouraged to identify any problems they had with the procedure and to make additional hypotheses about the test insect's behavior (e.g., perhaps the size of the insect affects the distance it moves).

Table 1.
Student procedures for the basic experiment.
1. Release one insect onto the arena at the starting mark. 
2. Use the manila folder to direct the insect's path so that it stays in the arena. Gently encourage the insect to move with the paintbrush or selected probe. 
3. Record starting and end points for each jump or movement. 
4. Repeat until the insect leaves the arena or after one minute. 
5. Repeat the procedure with a new insect. 
6. Measure the distance between each set of points and record. 
7. Determine the average jump or movement length for each individual insect. 
1. Release one insect onto the arena at the starting mark. 
2. Use the manila folder to direct the insect's path so that it stays in the arena. Gently encourage the insect to move with the paintbrush or selected probe. 
3. Record starting and end points for each jump or movement. 
4. Repeat until the insect leaves the arena or after one minute. 
5. Repeat the procedure with a new insect. 
6. Measure the distance between each set of points and record. 
7. Determine the average jump or movement length for each individual insect. 

To make this experiment more focused on inquiry-based learning, students can use the scientific method to make observations and develop hypotheses about insect behavior (Table 2). Students should observe insects in the wild and in captivity, then hypothesize what will make the insects move (vibrations on the table, loud sounds, air movement, tactile stimulus, etc.) or where the insects will go once they begin to move (toward light, toward darkness, to a high point, etc.; Table 3). As a control, the insect should be tested in the arena with no stimulus or arena modifications (just released at the starting point and any movement recorded for one minute). Then students can release a new insect of the same kind and employ the hypothesized stimulus and mark the insect's positions. To test hypotheses on direction of movement, students can modify the arena with dark hiding spots, extra light, or other features and then encourage the insect to move and observe where it goes. If the experiment includes two independent variables (e.g., the type of stimulus and the design of the area), only change one variable at a time so that changes in insect response can be attributed to the variable manipulated. To broaden the applicability of the experimental outcomes, different types of insects can be tested using the selected stimuli or arenas. Afterward, students can compare reactions between individuals of the same type and between different types.

Table 2.
Student procedures for the advanced experiment.
1. Observe the insect(s). Observe the insect(s) to be used and note behavior in regard to movement. 
2. Determine the hypothesis to be tested. From the observations, decide what can be tested and how. 
3A. Run the “no stimulus” treatment (negative control). a. Release one insect onto the arena at the starting mark. Limit student movement around the arena and do not prompt the insect to move. 
  b. If/when the insect moves, record starting and end points for each jump or movement for one minute. 
3B. If changing the arena, run the control stimulus treatment. a. Starting with a new insect, release it onto the unaltered arena at the starting mark. 
  b. Use a paintbrush to encourage the insect to move. 
  c. Record starting and end points for each jump or movement for one minute. 
4. Run the first experimental treatment (new stimulus/new arena). a. Starting with a new insect, release it onto the arena at the starting mark. 
  b. If your treatment changes the stimulus, use the new stimulus to encourage the insect to move. If your treatment changes the arena, use the control stimulus method. 
  c. Record starting and end points for each jump or movement for one minute. 
  d. Repeat the procedure with a new insect. 
5. Collect data  Measure the distance between each set of points and record. 
6. Analyze data a. Determine the average jump or movement distance for each individual insect. 
  b. Compare the different treatment distances to the control distances (e.g., compare the distance moved with arena alterations to the distance moved without arena alterations, or compare the distance moved without a stimulus to the distance moved with different stimuli). 
1. Observe the insect(s). Observe the insect(s) to be used and note behavior in regard to movement. 
2. Determine the hypothesis to be tested. From the observations, decide what can be tested and how. 
3A. Run the “no stimulus” treatment (negative control). a. Release one insect onto the arena at the starting mark. Limit student movement around the arena and do not prompt the insect to move. 
  b. If/when the insect moves, record starting and end points for each jump or movement for one minute. 
3B. If changing the arena, run the control stimulus treatment. a. Starting with a new insect, release it onto the unaltered arena at the starting mark. 
  b. Use a paintbrush to encourage the insect to move. 
  c. Record starting and end points for each jump or movement for one minute. 
4. Run the first experimental treatment (new stimulus/new arena). a. Starting with a new insect, release it onto the arena at the starting mark. 
  b. If your treatment changes the stimulus, use the new stimulus to encourage the insect to move. If your treatment changes the arena, use the control stimulus method. 
  c. Record starting and end points for each jump or movement for one minute. 
  d. Repeat the procedure with a new insect. 
5. Collect data  Measure the distance between each set of points and record. 
6. Analyze data a. Determine the average jump or movement distance for each individual insect. 
  b. Compare the different treatment distances to the control distances (e.g., compare the distance moved with arena alterations to the distance moved without arena alterations, or compare the distance moved without a stimulus to the distance moved with different stimuli). 
Table 3.
Examples of observations and treatments that could be used in the advanced experiment. Students should take time to make a few observations in order to formulate a hypothesis before beginning the experiment. Insects react to their environment in many different ways.
ObservationPotential Treatment (Stimulus or Arena Modification)Reasoning
Planthoppers climb the sides of the jar they are in. Arena modification with cardboard tubes (toilet paper or paper towel rolls) in one corner. Planthoppers like to be up high so that they have a clear area to jump if they feel threatened. 
Crickets move around a lot if there is a lot of noise. Clapping hands or snapping fingers as a stimulus. Crickets use sound to communicate to each other. 
Beetles will stop moving if they feel vibrations in the substrate they are on. Tapping on the arena to cause vibrations. Beetles may think that vibrations indicate a potential predator approaching and will stop moving so they do not draw attention to themselves. 
ObservationPotential Treatment (Stimulus or Arena Modification)Reasoning
Planthoppers climb the sides of the jar they are in. Arena modification with cardboard tubes (toilet paper or paper towel rolls) in one corner. Planthoppers like to be up high so that they have a clear area to jump if they feel threatened. 
Crickets move around a lot if there is a lot of noise. Clapping hands or snapping fingers as a stimulus. Crickets use sound to communicate to each other. 
Beetles will stop moving if they feel vibrations in the substrate they are on. Tapping on the arena to cause vibrations. Beetles may think that vibrations indicate a potential predator approaching and will stop moving so they do not draw attention to themselves. 

As with any experiment, it is important that students follow the instructions and perform each step as consistently as possible so that the data collected will be comparable. This is especially important when working in a group; students should try to be in the same positions around the arena for each replication and sample within. With either variation, students will need to measure the insect's movements at the end of the experiment. Each individual insect is a replicate, and each measured movement is a sample. Students should attempt to get 5–10 samples before the insect becomes fatigued (stops reacting to the stimulus), at which point the insect should be put back in its container and a new insect brought out to sample. They can calculate the average distance for each individual insect (from the samples), and then averages with respect to each type of insect, stimulus, or arena tested.

Materials & Preparation

Collecting and observing insects and developing a hypothesis should take ~45 minutes, but students should observe the insects' behavior for as long as time permits. The experiment should take ~60 minutes for groups to sample 5–10 insects each.

  1. Insects: Jumping insects, such as pinhead crickets, can be ordered from scientific supply companies or purchased at local pet stores. Students can capture other insects at home or on their school campus (beetles, crickets, grasshoppers, and planthoppers or leafhoppers will work well). Students should avoid flying insects because they will not work well in this experiment and many are dangerous to collect (e.g., wasps, bees, mosquitoes). Students should also avoid other common biting, stinging, or venomous arthropods, such as ants, spiders, and ticks. Try to collect at least 10 of each type of insect used. Insects should be placed individually in containers (plastic vials, Eppendorf tubes, or any small plastic container) immediately prior to beginning the experiment. To ensure healthy and active insects, collection should occur no more than 24 hours prior to the experiment, and preferably the morning of the experiment. Students should observe common safety practices, including using the buddy system, collecting only in areas designated by their instructor, and avoiding poisonous plants (e.g., poison ivy). Insects in containers should be kept at room temperature and out of direct sunlight. After the experiment, insects captured outside by students can be released; insects purchased should be put in a freezer overnight and then discarded.

  2. Materials per pair/group: The following items should be ready the day of the experiment: large sheet of paper (roughly 1 × 1 m; e.g., easel pad or roll of parchment paper), pen or pencil, paintbrush, cotton-tipped applicator or other items that can be used as probes, manila folder, insects in their containers, metric tape measure or ruler, and data sheets (Table 4).

  3. Testing arena: Use the large sheet of paper as the “arena.” Before releasing any insect, mark a starting point in a corner or near an edge for the basic experiment. The starting point for the advanced experiment should be in the center of the arena. The upright manila folder will later be useful for corralling the insect and keeping it in the arena.

  4. Student groups and individual tasks: Students should work in groups of at least two. At least one person should have eyes on the insect at all times so that no data points are missed and so that the insect is not lost if it leaves the arena. Minimally, one student should corral the insect with the file folder and stimulate it to jump using the paintbrush, and one should record the data points. Other students can help corral and keep an eye on the insect. With multiple observers, there is less of a chance that the insects' movements will be missed.

  5. A note on recording data points:

    • Jumping insects: Each point the insect jumps to needs to be marked. There should be two points for each jump: a beginning and an end. The insects will likely walk between jumps, and this distance is not recorded.

    • Walking insects: These data can be recorded two ways, either in discrete time increments (the location is recorded every 10 seconds) or the location is recorded whenever the insect stops moving. This should be decided before testing begins and with the nature of the insect in mind.

Table 4.
Example data sheet for the advanced experiment.
Insect Dispersal 
Observation Crickets are more active than planthoppers when it is noisy
Hypothesis Crickets are more sensitive to an auditory stimulus than planthoppers
Prediction If clapping is used as the stimulus, then crickets will travel a farther average distance than planthoppers
Data 
Treatment Species/Type Replicate Distance Jumped/Moved (cm) Average Distance (cm) 
Control (no stimulus) Planthopper 5, 7, 1, 10 5.75 
Planthopper 2, 3, 8, 11 
Cricket   
Cricket   
Stimulus 1 Planthopper   
Planthopper   
Cricket   
Cricket   
Stimulus 2 Planthopper   
Insect Dispersal 
Observation Crickets are more active than planthoppers when it is noisy
Hypothesis Crickets are more sensitive to an auditory stimulus than planthoppers
Prediction If clapping is used as the stimulus, then crickets will travel a farther average distance than planthoppers
Data 
Treatment Species/Type Replicate Distance Jumped/Moved (cm) Average Distance (cm) 
Control (no stimulus) Planthopper 5, 7, 1, 10 5.75 
Planthopper 2, 3, 8, 11 
Cricket   
Cricket   
Stimulus 1 Planthopper   
Planthopper   
Cricket   
Cricket   
Stimulus 2 Planthopper   

Example Discussion Questions

  1. After completing the first experiment (either the first replication of the basic experiment or the first treatment of the advanced experiment), did you learn or observe anything that helped you with the rest of the experiment?

  2. Is the behavior of the insect different when there is no stimulus versus when there is a stimulus, either tactile or a physical modification of the arena?

  3. How could human error affect the results of the experiment? (Hint: Think of the stimulus you applied. Was it exactly the same each time? How can you alter the experiment to make the stimulus identical every time?)

  4. Based on your measurements, how many jumps (or how long) would it take for the tested insect to move 1 m? 1 km?

  5. Is there a relationship between the insect's average body length and average jump distance?

  6. Do you think a good biocontrol agent disperses quickly or slowly? Why?

  7. Create a graph to visualize the relationships within your data. For instance, compare insect types with the average distance traveled, or compare the average distance traveled to the type of stimulus used.

Conclusions

Biological control is based on the idea that a specialized natural enemy of an invasive species can control populations of the invasive species in its adventive range. Most invasive species are spread by humans and often must get to the point that they are adversely affecting the invaded habitat before any management steps are taken to control them. By the time biological control agents are found, tested, and released, the invasive species has significantly impacted native species and altered the native habitat (McFadyen, 1998). This case study serves as an introduction to how scientists are identifying problems and researching solutions to them.

This biological control case study aligns with middle school level NGSS (Table 5). The advanced experiment integrates with the science and engineering practices of analyzing and interpreting data and connects the students with the nature of science through the use of the scientific method. Students are encouraged to graph their data, and this integrates the crosscutting concept of patterns. The influence of science, engineering, and technology on society and the natural world also can be incorporated into biological control as one of many technologies used to manage invasive species.

Table 5.
Next Generation Science Standards covered by this experiment.
Disciplinary Core Area Within This Activity 
LS2.A: Interdependent Relationships in Ecosystems Biological control agents rely on their host plants for sustenance and often exert population-controlling pressure on them. 
LS4.D: Biodiversity and Humans Many invasive plant species are spread by humans. In the case of water hyacinth, these plants can affect the biodiversity of a habitat by pushing out native species and impeding human use of the area by blocking navigation and water control structures. 
Practices Within This Activity 
MS-LS2-4: Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations. Invasive species alter habitats, affecting native plant and animal populations. In turn, biocontrol agents can affect their target invasive species populations. 
MS-LS2-5: Evaluate competing design solutions for maintaining biodiversity and ecosystem services. Biological control agents are used in addition to other control methods to manage invasive plants. 
Science and Engineering Practices Within This Activity 
Analyzing and Interpreting Data Students can analyze and interpret their data to accept or reject their hypothesis and to make additional observations about the insects. 
Crosscutting Concepts Within This Activity 
Patterns Students can create a graph to visualize their data. 
Influence of Science, Engineering, and Technology on Society and the Natural World Students can infer dispersal time and distance based on the patterns of movement and behavior they observed in their insects. 
Disciplinary Core Area Within This Activity 
LS2.A: Interdependent Relationships in Ecosystems Biological control agents rely on their host plants for sustenance and often exert population-controlling pressure on them. 
LS4.D: Biodiversity and Humans Many invasive plant species are spread by humans. In the case of water hyacinth, these plants can affect the biodiversity of a habitat by pushing out native species and impeding human use of the area by blocking navigation and water control structures. 
Practices Within This Activity 
MS-LS2-4: Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations. Invasive species alter habitats, affecting native plant and animal populations. In turn, biocontrol agents can affect their target invasive species populations. 
MS-LS2-5: Evaluate competing design solutions for maintaining biodiversity and ecosystem services. Biological control agents are used in addition to other control methods to manage invasive plants. 
Science and Engineering Practices Within This Activity 
Analyzing and Interpreting Data Students can analyze and interpret their data to accept or reject their hypothesis and to make additional observations about the insects. 
Crosscutting Concepts Within This Activity 
Patterns Students can create a graph to visualize their data. 
Influence of Science, Engineering, and Technology on Society and the Natural World Students can infer dispersal time and distance based on the patterns of movement and behavior they observed in their insects. 

Understanding the dispersal capabilities of a biological control agent is useful for determining release and monitoring methods, as well as estimating the impact of that agent on its target. To increase the relevance of the classroom findings to predicting how the insects will disperse in the wild, additional experiments can be conducted that simulate environmental stimuli or involve aspects of the insect's biology. Some factors influencing insect dispersal include distance between habitats or food sources (Haddad, 1999), wind (McClure, 1990; Asplen et al., 2016), temperature (Lachenicht et al., 2010), life span (David et al., 2015), sex (Asplen et al., 2016), population density (Herzing, 1995), and competition (Baines et al., 2014). While this experiment was originally designed to answer part of a larger question regarding the dispersal of a biological control agent in the landscape, it can be presented alone, with the methodology intact, to middle school students as a great introduction to entomology and scientific research. This experiment allows students to experience entomological research in the classroom, can easily be modified for different class times and levels, and is low cost. Students are able to practice using the scientific method to make observations and develop hypotheses to explain insect behavior while collecting their own, unique data using living organisms. Students can also use their observations to suggest modifications to the described protocol or additional experiments that could be conducted. The use of live insects makes this experiment fun and exciting for students and opens up the opportunity for discussion of research methodology, the ecological importance of insects, and animal behavior, among others.

We thank Jeremiah Foley at the USDA-ARS Invasive Plant Research Laboratory for the initial experimental design, and Hope and James DePelisi at Broward County Crime Commission for inviting us to present at the CSI:STEM Summer Camp. We also thank Eileen Pokorny, Brittany Knowles, and Ryann Valmonte at the USDA-ARS Invasive Plant Research Laboratory for rearing the planthoppers (Megamelus scutellaris) used.

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