Name: ______Period: ______Date: ______

Bess Bugs Lab

Are you stronger than an insect?

A comparative look at form, function, and strength

Objective: In this exercise, you are going to use bess beetles to explore the relationship between strength and body size and learn how body structure influences strength.

Introduction:Today we are going to be working with bess bugs, also known as Odontotaenius disjunctus. These bugs resemble large beetles and have shell-like forewings called elytra, which function as a tough shield for their soft wings and abdomen. Although they do have functional hind wings, these beetles rarely fly. When disturbed, these beetles make a squeaking noise by rubbing their elytra against their abdomen. This is known as stridulation and is used for different types of communication, which is especially important since bess beetles live the majority of their life in complete darkness. Adult beetles can grow up to 4 cm long; and each beetle has 6 legs and 3 body segments. These insects are very important in the recycling of dead wood and there are only two species found in the United States. The most recognizable features of these beetles are the gold-colored fringe on its legs and the edges of its body, the protruding small horn on the beetle’s head, strong mandibles, and feathery antennae.

NOTE: During this lab you will be working with a living organism. You are to show your beetle respect and any beetles harmed or killed during this experiment will result in a failing grade. Bess beetles have pinchers and can pinch, however seldom do. The best way to pick up a beetle is to use two fingers placed gently on either side of its abdomen with your thumb and forefinger. The beetle can then be placed on an open palm.

PRELAB - Completed on Day 1 of the lab.

Parts A & B: Making Observations

Intro to Bess Beetles

  1. After getting into small groups, select a beetle to use for your experiment and note the color of the mark on its back on your lab worksheet.
  • Pass the beetle around so that all students in your group can get a close look – they can’t bite or hurt you; just remember to be gentle.Don’t forget to record your answers and initial observations on the lab worksheet for parts A and B.

Preliminary Measurements

  1. Weigh a Petri dish and record the mass in your data table on the lab worksheet, then place the beetle in the Petri dish upside down and record the mass, subtracting the two to get the weight of the beetle and record on your data table.
  1. Measure the length, width, and height of the beetle and record on your data sheet.
  1. Weigh the object that you will use for weights (i.e. pennies, dimes, washers) and record on your data sheet.

Part C: Forming a Hypothesis

Insects have been known to be relatively strong for their size. We want to see what percentage of the bug’s massit can pull. Watch the video clip on one of the “World’s Strongest Men” and record your observations of the attributes that contribute to his extraordinary strength and use that to make an educated prediction (also known as a hypothesis) about the relative strength of your bess beetle compared to your own relative strength. Note: the average human can lift approximately as much as he weighs.

EXPERIMENT - Completed on Day 2 of the lab.

Part D: Data Collection

You will need the following materials to complete this experiment:

- bess bugs (you will record data for individual beetles; they will be marked)

- paper towel or some material to aid in traction

- long piece of string (waxed dental floss works well)

- numerous small weights (pennies, dimes, washers)

- triple-beam balance

- Petri dish

- 2 metric rulers

- tape

- calculator

- data sheet/lab worksheet

Procedure:

You are going to see how much weight a beetle can pull by tying a string around its abdomen and adding different weights. This will not hurt the beetle. Ultimately, you will be able to compare the relative strength of a human and a beetle.

REMEMBER!!! These are living organisms. Care should be taken when handling and during the experiment not to cause stress or endangerment of the insect. If you think the beetle is overly stressed, place it back in the terrarium and work with another beetle.

1. First, you will need to create a harness for your bess bug. Remember to be very gentle as you attach the string to the beetle. Have one person tie a knot in the string, but do not tighten. Use a slip knot or other knot that is easy to remove. Have another person hold the beetle while the string is slipped over the beetle’s head to its thorax (middle section) and gently pull the knot secure. Make sure the string will be easy to remove! It does not need to be tightened very much.

2. Next, you will take the remainder loop of string and attach a Petri dish to the end of the string with tape. The beetle may squeak when you are doing this.

3. For the experiment, it will help if the beetle is on a rough surface so that it can get traction. Table tops don’t work too well, a good idea is to tape paper towels to your desk.

4. Next, place your bug at the beginning of the carpet (paper towel). Take one of your weights and add them to the Petri Dish.Have your bug try and pull the weight. Try to “assist” your bug so it pulls the weight in as straight of a line as possible (use the rulers to assist your bug in going in a straight line). Gently lift up the beetle and place it at the starting line (or if you have enough room, let the beetle keep going).

5. Slowly add more weights, one at a time, to the Petri dish, and allow the beetle to walk. The beetle may need to be repositioned, but try not to disturb it too much.

6. When the beetle can barely or no longer pull the weight you add, remove the string from the Petri dish, the harness from the beetle and gently place it back into its home. Don’t forget to record the number of weights your beetle pulled in the second data table. Use this number and the mass of one washer from the first data table to record the total mass pulled by the beetle.

7.To complete the data tableyou need to calculate the pulling power of your bug. To do so you should use the following formula:

Massbeing pulled

------=pulling power of bess bug

Massof your bug

8.Once you have this numbercalculated, RECORD THIS VALUE INYOUR DATA TABLE.

9. As a class we will now calculate the class average for pulling power. RECORD THIS VALUE IN YOUR DATA TABLE.

Part E: Analysis and Conclusions

Complete the questions on the lab worksheet and construct a graph using the pulling power of the beetles used during the experiment.

  • Now that you know how strong a beetle is – apply that knowledge to think of a question that could be answered through a scientific experiment. For example: Can two beetles working together pull twice the weight of one beetle?
  • Using Microsoft excel, construct a BAR GRAPH in which you compare your bess bug’s

pulling power and thepulling power of the other beetles used in the experiment to the class average for pulling power. Your graph will havemultiple bars, should take up as much of the paper as possible, and should have two clearly labeled axes and a clear, detailed title. Please attach it to the back of the lab worksheet.

  • The number of bars will depend on how many groups collected data for the lab.