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A study of the relation between vegetation and insects

A study of the relation between vegetation and insects

Introduction: (Initial Observation)

While walking in a hiking trail in a nearby park, I noticed that large numbers of mosquitoes are gathered in certain spots while just a few yards away, there was almost no mosquitoes. It was obvious that mosquitoes are not distributed evenly across the park. I was wondering what makes mosquitoes gather in one spot? Do mosquitoes have homes, cities, and villages where they gather or they are just wondering around and travel by wind?

While thinking on these questions I also thought there might be a relation between the type of vegetations and mosquitoes in the park. In other words, there might be certain plants that attract mosquitoes and form small mosquito infested areas.

With this experience (many other people may have experienced the same), I decided to study on the relationship between plants and insects. I may go back to the park and record the type and condition of plants in areas with and without mosquitoes. This may help me identify certain plants that attract mosquitoes or certain plants that repel mosquitoes.


If you have any questions, click on the help button at the top of this page to send me your questions. I may respond by email, but often I update this page with the information that you need.

Project Advisor

Why this project is important to me? How can I benefit from it?

I think the information that I collect and the results of my research may help me choose the right type of plants for my backyard. I might be able to find plants that do not attract mosquitoes and flies, but instead attract butterflies.

Information Gathering:

Find out about interrelations between plants and mosquitoes. Read books, magazines, or ask professionals who might know in order to learn about the plants that attract or repel pest insects. Keep track of where you got your information from. Following are samples of information that you may find:

The honey and pollen in the flowers of plants provide delicious foods for insects; while insects also pollinate for the plants in the process of seeking foods; and this is a supplementary relation in-between many plants and insects in the biological field. However, many plants and insects are not exclusive in such relations, i.e. the flowers of one kind of plant can provide foods for many kinds of insects, and one kind of insects can also pollinate for many kinds of plants.


What is most remarkable is that plants are not only able to repel insect pests – but also, and simultaneously, produce compounds which are attractive to the natural predators of the insect pests. Source…

Herbs That Repel Insects

Many people ask us which herbs repel insects. So what herb plants are effective for chasing away those pesty pets? The following is a list of Herb plants in alphabetical order with the pest they chase away. Remember, you must occasionally bruise or rub the leaves to activate the fragrances that do the chasing!

Common Name Botanical Name Pests Repelled
Holy Basil Ocimum sanctum flys and mosquitoes
Lavender Laverdula mosquitoes and gnats
Lemon Balm Melissa officinalis mosquitoes and gnats
Lemon Thyme Thymus x citruidirus mosquitoes and gnats
Mexican Marigold Tagetes minuta mosquitoes and gnats
Mugwort Artemisia vulgaris moths
Pennyroyal mint Mentha pulegium fleas and ticks
Pyrethrum Chrysanthemum cineriifolium mites, aphids, and leaf hoppers
Santolina Santolina chamaecyparissus all insects
Scented Geranium (Lemon Rose) Pelargonium graveolens mosquitoes and gnats
Southernwood Artemisia abrotanum moths
Tansy Tanacetum vulare ants

Santolina has been found to be the most effective insect repellent in the garden. Plant several plants in the corners of your gardens and rub them every day.


Many herbs contain essential oils with mosquito repelling properties.

A research in Iowa State University Department of Entomology indicates that an essential oil in catnip is 10 times more effective at repelling mosquitoes than potent chemicals such as DEET.

DEET is currently the most common active ingredient in commercial mosquito and bug repellents. Source…


Catnip is a multi purpose plant. The tea is very pleasant and has a lemon-mint flavor and fragrance. Catnip is also a recreational herb for cats. Toys stuffed with catnip will provide them with hours of entertainment. Catnip is hardy and grows in almost any soil.

Various herbs have been used for centuries to help keep mosquitoes from landing on skin and biting. However, over the last century with the emergence of new products containing synthetic chemicals such as DEET, many common herbs with insect repelling qualities are no longer being used. However, plants can be used to repel many biting insects.


Mosquitoes Need Water: All mosquitoes have four stages of development (egg, larva, pupa, and adult) and spend their larval and pupal stages in water. The females of some mosquito species deposit eggs on moist surfaces, such as mud or fallen leaves, that may be near water but dry. Later, rain or high tides reflood these surfaces and stimulate the eggs to hatch into larvae. The females of other species deposit their eggs directly on the surface of still water in such places as ditches, street catch basins, tire tracks, streams that are drying up, and fields or excavations that hold water for some time. This water is often stagnant and close to the home in discarded tires, ornamental pools, unused wading and swimming pools, tin cans, bird baths, plant saucers, and even gutters and flat roofs. The eggs deposited on such waters soon hatch into larvae. In the hot summer months, larvae grow rapidly, become pupae, and emerge one week later as flying adult mosquitoes. A few important spring species have only one generation per year.


Excess nitrogen attracts many insects, such as aphids. The stress attracts insects, which in turn attracts the spiders. Excess fertilizer and chemical pesticides also kill off beneficial bacteria which in turn causes stress in the plants. All stressed plants attract insects. Indoor plants that are stressed will especially attract insects, and spiders.


Question/ Purpose:

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 this project is to find out the relation between verities of vegetation and pest insects such as mosquitoes.

Question: How do plants affect the population of mosquitoes in an area.

Identify Variables:

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.

Independent variable is the type of plants (that we can find, identify, observe and examine)

Dependent variable is the population of mosquitoes around the plant (or attraction & repelling properties of the plant)

Controlled variables are all other environmental variables that may affect accumulation of mosquitoes in a certain area. Controlled variables include:

  • Light
  • Temperature
  • Wind
  • Moisture


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.

My hypothesis is that certain plants produce volatile compounds and essential oils that naturally repel mosquitoes while some other plants may produce sap that attract mosquitoes.

Experiment Design:

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.”


Identify plants, mosquitoes proximity in a certain area

Introduction: We record the type of plants where we see a mosquito population. We also record the type of plants where we see no mosquitoes. The information that we gather may show a clear relation between mosquito population and presence of certain plants.


Identify an area with varieties of plants for your study.

Make a general observation of the plants in the area and try to identify them. You may need to ask others, visit a library, or search some internet websites for identifying plants.

Ignore the plants that you can not identify unless your further observations show that those plants may have a noticeable effect on attracting or repelling mosquitoes.


Visit the area and locate the places with no mosquitoes or a large population of mosquitoes. Mark and name or number each location.

Record the name of plant or a list of plants in each location.

Record your results in a table like this:

Data table for date:……………….. Temperature:……………. wind speed….

Location Types and condition of plants Mosquito population

For each location that you mark, go back and revisit the location at least 2 more times and record your observations again. Visits can be 1 to 10 days apart. Compare your results tables from different visits. The type of vegetation usually does not change from one visit to the other. Does the population of mosquitoes change?

If you see any change in the population of mosquitoes, can it be contributed to other factors such as temperature and wind?

Experiment 2:

Plants that attract or repel mosquitoes

Introduction: If certain plants can attract or repel mosquitoes, we must be able to examine and observe such properties in a mosquito chamber.

Mosquito chamber also known as olfactometer is a sealed clear Plexiglas container (often with controlled temperature and moisture) that is used to observe and test the effects of different chemical or physical conditions on adult mosquitoes.

At home, you may cover the opening of any glass or Plexiglas container with a very fine net and use it as a mosquito chamber. Just make sure that the opening is large enough for you to take your hand in and out while you are holding smaller containers of food or water.

An empty jar or aquarium placed on its side and properly covered with fine net can be used as an olfactometer at home.


Prepare a cage or olfactometer with one side covered by a fine net. Draw two circles of about 6″ diameter on three different areas of the net. Number the areas 1 and 2.

Populate your olfactometer cage with adult mosquitoes by providing water and food to mosquito eggs. Mosquito eggs can be purchased or obtained from mosquito research agencies. Click here to learn about different stages of mosquito growth and where you may possibly be able to obtain eggs. At a temperature of 75蚌 to 80蚌, you can complete the mosquito growth cycle in about 10 to12 days .


  1. Shake the net so all mosquitoes get disturbed and get away from the net.
  2. Hang a piece of green construction paper cut in the form of a leaf in the center of the area #1 of the net.
  3. After 3 minutes observe the population of mosquitoes on the net and around the paper leaf. See if mosquitoes are attracted or repelled from the paper leaf. Count the number of mosquitoes on the circles number 1 and two.
  4. Divide the number of mosquitoes in area #1 by the number of mosquitoes in area number 2. This will be the rate of effect.
  5. Repeat steps 1 to 4 by varieties of different real plant leaves, especially household plants and herbs that you can find.
  6. For each plant repeat the experiment about 3 times and each time place the leaf in a different area of the net.
  7. Record the rate of effect for each of your experiments in a table like this:
    Plant Try 1 Try 2 Try 3
    Paper Leaf
    Geranium leaf

Use your results table (above data table) to calculate the average of data that you collected in 3 different tries on each type of leaf. Record the average results in a table like this:

Plant Average rate of effect
Paper Leaf
Geranium leaf

In the above table, numbers larger than 1 indicates mosquito attractor and numbers smaller than 1 indicates mosquito repeller.

Note: instead of hanging a leaf, you could extract the juice and essential oils of the leaf and rub them in your hand and then insert your hand in the cage to see how many mosquitoes will sit on your hand; however, this could result mosquito bites.

Also visit the following link for additional information.


and this that may not be quite related:


Materials and Equipment:

List of material can be extracted from the experiment section.

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.


For experiment number 2, you must calculate the average rate of effect of your three trials with each kind of leaf.

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. Write which plants possibly repel the insect you studied.

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.

Possible Errors:

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.