Growth in Hornworm Mass (Mark Rothenay)

Research Question and Hypothesis

Research Question: How can the amount of light exposure that helps contribute to the activity level of Hornworms (Manduca sexta) affect its growth?

Hypothesis: The greater the amount of light exposure will cause an increase in the hornworm mass due to more foraging time.

Standards

HS-LS2-6 Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.

HS-LS2-1 Use mathematical and/or computational representations to support explanations of factors affecting the carrying capacity of ecosystems at different scales.

Experimental Design

Students will observe and record the growth in hornworms that are grown in environments with varying light exposure. This species has a fast growth rate in normal conditions so the students will conduct this investigation over a 11 day period. In the end, students will analyze their data and determine which exposure of light frequency was best at either growing the worms at a faster and slower levels. This in part will hep assist the hornworm cultures grown in the classroom so not all worms mature at the same rate. This will then help having a food supply that caries in sizes for the classroom reptiles. Other variables such as temperature can also be tested for future experimentation.

Note: This experiment can also be conducted with silkworms (Bombyx mori) and instead of using the hornworm diet, mulberry leaf or a similar diet formulated for silkworms can be used.

Independent variable

The independent variable will be Time. Three settings will be used (i.e. T-8, T-10, T-12)

Dependent variables

The dependent variable will be the rate of growth measured in the worms mass (grams).

Series

The rate of mass growth (dependent variable) as a function of the amount of light (independent variable) for a 10 day period (series).

Constants and Controls

Constant: The number of hornworms in each cup, the amount of food in each cup, the size of the container, same temperature for each cup.

Control: Our control group will be the cup marked as 10 since this is close to how many hours of sunlight we receive on a normal day in the month of November for a latitude of 34 degrees.

This calendar might be useful to those who wish to determine the amount of sunlight hours in a day depending on the month.

Materials

1. 500 ml hornworm cups. Any plastic cup with lid with holes for airflow will work.

2. Hornworm diet.

Please note that hornworms fed tomatoes should not be given as a feeder insect since the worm will bioaccumulate the alkaloids (tomatine) present in the tomato leaf and is toxic to reptiles.

3. Hornworms. Can be found at local pet store that specializes in reptiles/amphibians or online.

4. Light timers.

5. Light source that can be manipulated by timer.

6. Scale. Any scale that measure in grams.

Procedures

1. Label the first cup with the number 8. Label the next cup with the number 10. Label the last cup with the number 12.

2. Place hornworm food (100ml) into each cup with the mesh.

3. Weigh each hornworm in grams and collect data in a data table for later analysis. Place at least 3 hornworms in each cup. If you want to do more you can but make sure each cup receives the same approximate size and number of hornworms.

4. Place the first cup with the number 8 in a dark located and set up a light in this located that is connected to a timer set for 8 hours of light. Keep this as the only source of light until measuring then return.

5. Place the control cup with the number 10 in an area that receives indirect sunlight.

6. Place the cup with the number 12 in another dark location that has a light hooked up to a timer set for 12 hours of light. Keep this as the only source of light until measuring then return to its location.

7. On the initial day, measure each cups mass in grams of the hornworms and record the data in a data table. Take the average mass.

8. Every second day, measure each cups mass in grams of the hornworms and record the data in a data table. Take the average mass.

9. On the final day (day 11), record the final mass of the hornworms in grams. Take the average mass.

10. Graph data using the average mass of the worms on each day measured.

Sample data and graphs

Analysis & Conclusions

Looking at the data, it is noticeable the mass did increase with an increase in light duration. It was observed the hornworms did have more foraging behavior in the higher amount of light. The difference between the 8 and 10 hour is slightly noticeable in the growth. What was rather interesting is that when the worms reached approximately 9.0 grams in mass, they reduced their foraging behavior and moved to the bottom of the container. It appears at this stage they start their morphing into their adult stage. Further investigations that have more variables with increases in time such as 14 and 16 hours to see if this will have an affect on their growth and by how much.

Photos & Movies

References

Breeding hornworms