Introduction: (Initial Observation)
Mosquitoes are nuisance insects that bite and bother people. Where populated, mosquitoes may fly in to our eyes, ears, mouse and nose. Some mosquitoes carry deadly disease such as West Nile Virus, dengue, yellow fever, and malaria. By learning about a stimuli that attract mosquitoes we may attract mosquitoes into traps or attract them to environment away from ourselves. Stimuli can be anything that can cause a response or reaction. Possible stimuli for mosquitoes are certain sounds, odors, lights and colors.
For experiments of this project you need to have access to an area with lots of mosquitoes.
Find out about what you want to investigate. Read books, magazines or ask professionals who might know in order to learn about the effect or area of study. Keep track of where you got your information from.
Mosquito life cycle is less than one month. On average, a female mosquito will live 2-3 weeks, but the male’s lifespan is shorter. Within their lifetime both adult male and female will feed on nectar and plant fluids, but it is only the female that will seek a blood meal. The majority of species require this blood meal as a protein source for egg development. Female mosquitoes are attracted to a potential host through a combination of different stimuli that emanate from the host. The stimuli can include carbon dioxide, body odors, air movement or heat. Upon locating a suitable host, the female will probe the skin for a blood capillary then inject a small amount of saliva containing chemicals which prevent the host’s blood from clotting. This is often the pathway for potential pathogens such as viruses to enter a host. After engorging on the host’s blood the female will find a resting place to digest her meal and develop eggs before flying off to deposit them in a suitable aquatic habitat.
On hatching, the young larvae (wrigglers) feed continuously and grow through four different instars or moults. Larval development is dependent on the availability of food and prevailing conditions, particularly temperature, but generally takes at least one to two weeks.
The final larval instar develops into an active comma-shaped pupa (tumbler) from which the adult mosquito emerges (image on the right) about 2 days later to feed, mate and develop eggs for the next generation.
Scientists have known for decades that mosquitoes are drawn to carbon dioxide, exhaled in abundance by the animals that hungry mosquitoes favor. Carbon dioxide doesn’t tell the whole story, though.
Mosquitoes, after all, tend to bite people on the arms and legs. “I can’t imagine that much carbon dioxide coming off of someone’s hand,” says Ulrich R. Bernier, a chemist at the U.S. Department of Agriculture’s Agricultural Research Service (ARS) in Gainesville, Fla. “And how often do mosquitoes fly into your mouth or nose?”
Carbon dioxide is clearly important, but the skin must give off other attractants, too, he reasons.Continue …
When humans or animals breath out they produce CO2, and their bodies are constantly giving off heat and moisture. Mosquitoes and other biting insects have the ability to detect CO2, heat and moisture from long distances and are immediately attracted to the source. Mosquitoes are also attracted to trace amounts of alcohol vapor as well as dark colors, especially black. The mosquitoes fly around and search using their sensors for a warm body to start biting. Continue …
Many mosquitoes were trapped by contraptions that mimic a human being: a trap with a tiny light bulb and a tub of dry ice that slowly leaks carbon dioxide to mimic people’s breath. When mosquitoes fly up to investigate the light or the carbon dioxide, they are trapped in a cylindrical net.
Another device attracts mosquitoes with a tray of slimy peat to entice females to lay their eggs.
In experiments, entomologists have discovered that mosquitoes prefer skin that is warm—over 90 degrees F. Human beings’ temperatures vary, but the average is between 87 and 95 degrees. This may explain why there are always a few maddening individuals at a summer gathering who say, “That’s funny, I’m not being bitten at all.”
The entomological conclusion: take cold showers—every ten minutes or so! —to lower your skin temperature. You might also give up alcoholic beverages and mild exercise—both warm the skin several degrees. (Exercise violent enough to cause profuse sweating tends to discourage mosquitoes.) And while you’re at it, wear only light-colored clothing. Like most insects, mosquitoes have definite color preferences; many kinds are attracted to black, dark reds and blues. White, yellow and light green are the least appealing. Continue …
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of our investigation is to identify and study different stimuli that attract mosquito.
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Each stimuli that we choose to study is an independent variable. The reason that we call them independent variables is that we want to change their values in order to find the effect of such changes on our dependent variables. Dependent variable will be the rate or the number of mosquitoes that are attracted.
Following are a list of independent variables that we may choose from to study.
- The rate of carbon-dioxide in the air
- Dependent variable is the number of or the rate of mosquitoes that are attracted.
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. For each variable that you choose to study, you must propose one hypothesis. Following are some examples:
- I think temperature is not a necessary factor in attracting mosquitoes. My hypothesis is based on my previous observation of mosquitoes sitting on sweet fruits that are at room temperature. However heat may be effective in attracting female mosquitoes when they are ready to lay eggs because at that time they need to eat some blood.
- My hypothesis is that moisture is an stimuli that attracts mosquitoes when they are thirsty or they want to lay eggs.
- I think carbon-dioxide is an effective stimuli for attracting mosquitoes. My hypothesis is based on my gathered information and my observation of mosquitoes flying around my face and my mouth when I go jugging or hiking.
- I don’t think that mosquitoes have any color preference, so color is not an effective stimuli in attracting mosquitoes.
- Propose a hypothesis for odor as an stimuli
- Propose a hypothesis for sound as an stimuli
- Propose a hypothesis for food as an stimuli
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
In order to identify the effect of different stimuli in attracting mosquitoes we need to have a method of trapping or capturing mosquitoes. This allows us to count the number of mosquitoes that are attracted to each stimuli within a certain period of time and compare it with the number of mosquitoes trapped without any stimuli.
How to capture or trap mosquitoes?
Two commonly used methods of capturing mosquitoes are vacuum trap and sticky trap.
Construct a vacuum trap
Mosquitoes are very small and light insects, so any air current can force them out of their path and drag them into a trap. This is the technique used in vacuum traps also known as New Jersey Light Traps. Vacuum traps contain an electric fan that sucks air from one direction and blows it into a net.
This net is where the mosquitoes will be trapped in. In most designs air is sucked from the top and blown down into the net. That is good because the gravity will also help mosquitoes to get into the trap. This trap is perfect for testing different color lights as stimuli to attract mosquitoes, however it can be used for other experiments as well. Light traps will work best where there are no other light sources around such as rural areas.
To construct a simple vacuum trap at home you can attach a net to the front of an electric fan, so the fan will blow in the net. When selecting the net fabric, choose a fine knitted net so the mosquitoes can not pass through openings. Net can be attached to the fan with different methods. One possibility is using wooden cloths pins to do that. The net can be a simple piece of net or it can be sewed to form a sack.
Construct a sticky trap
Sticky traps are usually some kind of adhesive material coated on a strip of paper or sheet of cardboard.
You can purchase them from hardware stores or try to build one yourself. Either way you may mount them on a wood or plastic board using some masking tapes.
If you want to make s sticky board yourself, you might be able to do this by making a strong solution of sugar. The result should be something like honey but with less viscosity. To stop sugar from crystallization you may add some citric acid to the solution. You will need to heat up the solution until enough sugar dissolves and proper viscosity is achieved. Then cover one side of a board with your sticky solution.
Sticky trap shown on the right is composed of 3mm thick plastic board measuring 200mm x 300mm. These boards were then covered with a transparent film covered in adhesive. The adhesive film was cut to size to cover the plastic boards and held in place using masking tape. Boards were baited with various odors contained within plastic bottles, these were fixed to the traps by cutting holes in the center of the board and screwing the threaded neck of the bottle into the hole. This allowed us to change the bottles and test different odors.
Making a varieties of traps and testing them is an important part of this project. You must make sure that you have a method of capturing and counting the mosquitoes.
Testing temperature as a stimuli
- Find a place with many mosquitoes (backyard, terrace, …)
- Prepare five plastic containers with five different temperatures. Do this by filling up the containers with hot water, warm water, no water, cold water and ice water. (No water is the same as room temperature water).
- Name the containers (hot, warm, normal, cold, icy).
- Seal all containers so they do not release moisture.
- Get five identical same size sticky traps. Place one sticky trap on each container.
- Make observations every 15 minutes and record the number of mosquitoes trapped on each trap.
- Continue your observations for 3 to 6 hours.
Record the results in a table like this:
Count of trapped mosquitoes with different trap temperatures
Depending on the number of mosquitoes in your experiment area you may reduce or increase observation/count intervals and the total experiment time.
Make a graph:
The best graph for this project is a bar graph used to show the final number of mosquitoes. Make 5 vertical bars and name them icy, cold, normal, warm and hot.
The height of each bar is the total number of mosquitoes trapped in that temperature. Write the numbers on the top of each bar.
You may optionally draw a separate graph for each time period. For example one graph for 15 minutes, one graph for 30 minutes or so on; however, I don’t think that it is necessary.
Testing Moisture as a stimuli
- Find a place with many mosquitoes (backyard, terrace, …)
- Take two empty plastic buckets.
- Add about one inch of water to one bucket (to create moisture)
- Place a brick at the bottom of each bucket (it should not submerge in water. Break is a stand for our sticky trap. It will also assist in sucking the water and distributing it to the air in the form of moisture).
- Prepare two identical sticky traps.
- Place one sticky trap on the top of the break on each bucket.
- Make observation and count the mosquitoes on each trap after 24 hours.
Testing Carbon dioxide as a stimuli
- Find a place with many mosquitoes (backyard, terrace, …)
- Take two empty plastic buckets.
- Place one brick at the bottom of each bucket
- Prepare two identical sticky traps.
- Place one sticky trap in each bucket on the top of each brick.
- In one bucket drop a piece of dry ice (Almost the size of a soap bar).
- Make observations every 30 minutes for 3 to 6 hours and record the results.
Note: Dry ice is solid Carbon Dioxide. It is very cold. Handle it with gloves and spoon. It will change back to gas at room temperature. Since carbon dioxide is heavier than air, bucket will remain full of CO2 even after dry ice is fully sublimated. In many areas there is a local distributor for dry ice (check your local directory).
If you don’t have access to dry ice, you can add 1 inch carbonated water (such as seltzer) to one bucket and one inch tap water to the other bucket. Carbonated water will gradually release carbon dioxide and water in the other bucket is just to make sure that both buckets have the same moisture. To accelerate release of carbon dioxide you may drop a cube sugar in the bucket with carbonated water.
Testing color as a stimuli
- Get six small shoe boxes and cover them with color paper or paint them. You need black, white, yellow, blue, green and red.
- At the bottom of each box place one sticky trap.
- If the experiment area does not have many mosquitoes, you may also place a few drops of a sweet juice under each trap to help attracting mosquitoes.
- Make observations. Count the mosquitoes in each trap and record the results in a table.
All other experiments may follow the same style.
For all the above experiments we used sticky trap instead of vacuum trap because it is more available and more affordable for students.
Materials and Equipment:
List of material can be extracted from the experiment design.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
No calculations are required for this project. however you may need to convert the mosquito counts to percentage. For example in experiment number 1 it is more helpful if you report what percentage of the total captured mosquitoes are captured on each trap. To do that you divide the number of mosquitoes captured on each trap by the total number of mosquitoes captured in all five traps.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
List of References
Mosquito Control Districts:
- Alameda County Mosquito Abatement District
- Amelia Island Mosquito Control District
- Beach Mosquito Control District
- Broward County Mosquito Control Section
- City of Winnipeg’s Insect Control Branch
- Collier Mosquito Control District
- Contra Costa Mosquito and Vector Control District
- East Flagler Mosquito Control District
- East Middlesex Mosquito Control Project
- Florida Keys Mosquito Control District
- Greater Los Angeles County Vector Control District
- Los Angeles County West Vector Control District
- Lee County Mosquito Control District
- Leon County Mosquito Control
- Levy County Mosquito Control
- Manatee County Mosquito Control District
- Marin/Sonoma Mosquito Vector Control District
- Marion County Mosquito, Rodent and Environmental Control
- Metropolitan Mosquito Control District
- Miami-Dade Mosquito Control
- Monmouth County Mosquito Extermination Commission
- New Jersey Mosquito Biology and Control
- Norfolk County (Massachusetts) Mosquito Control Project
- Plymouth County Mosquito Control Project, MA
- Sacramento-Yolo Mosquito and Vector Control District
- Saginaw County Mosquito Abatement Commission
- San Mateo County Mosquito Abatement District
- Santa Barbara Coastal Vector Control District
- Santa Clara County Vector Control District
- Shasta Mosquito and Vector Control District
- Tuscola County Mosquito Abatement
- Utah County Mosquito Abatement Division
Mosquito Control Associations:
- Associated Executives of Mosquito Control Work in New Jersey
- Florida Mosquito Control Association
- Louisiana Mosquito Control Association
- Michigan Mosquito Control Association
- Mid-Atlantic Mosquito Control Association
- Mosquito and Vector Control Association of California
- Mosquito Control Association of Australia Inc.
- New Jersey Mosquito Control Association
- North Carolina Mosquito and Vector Control Association
- Northeastern Mosquito Control Association
- Northwest Mosquito and Control Association
- Pennsylvania Vector Control Association
- South Carolina Mosquito Control Association
- Texas Mosquito Control Association
- Utah Mosquito Abatement Association
- Virginia Mosquito Control Association
University and Medical Lab Sites:
- ACITHN. Medical Entomology
- California Vector-borne Disease Surveillance System
- EXTOXNET, The EXtension TOXicology NETwork
- Florida Medical Entomology Lab
- Harvard School of Public Health, Mosquito-Borne Viruses
- USDA Center for Medical, Agricultural and Veterinary Entomology (CMAVE)
- John A. Mulrennan, Sr. Public Health Entomology Research and Education Center
- Mosquito Genomics WWW Server
- MosquitoNet Control of Mosquitoes and Other Vectors of Human Disease
- Society for Vector Ecology (SOVE)
- Tulane Tropical Medicine
- University of California Mosquito Research Program