Aquatic Insects Sampling Lesson

Aquatic insects live underwater and perform important tasks such as filtering water and breaking down dead plants. Many aquatic insects are very sensitive to pollution. Pollution can make it hard for aquatic insects to breath under water, and can cause rocks that insects walk on to become slippery. Some insects are not so sensitive to pollution because they come to the surface to breath, or because they don’t need to walk underwater.

Equipment list:

- Sampling net
- Boots (2 pairs)
- White tray
- Bucket
- Water bulbs
- Tweezers (also called forceps)
- Ice cube trays
- Plastic vials for insect storage
- Gloves
- Biotic index of water quality
- Data sheet
-Magnifying glass (2)

Directions:

1.   Choose a section of the river that is not very deep and where the water has ripples. Set up your white tub nearby with some water in it.

2.   Collectors should put on their boots and gloves.

3.   One collector should place the net so that the bottom lies on the floor of the river. Another collector should turn over as many of the rocks as possible upstream from the net for one minute. Run you hands over some of the rocks to wipe off clinging insects.

4.   After one minute, gently remove the net from the water and carry it over to the tub. Put it upside-down over the tub and use the water bulbs to wash insects into the tub. You can use tweezers to pick out the insects that don’t wash out. Be very thorough – make sure to look under all the leaves.

5.   Stop! Check to see if you have enough time to do the next three steps. If not, continue later.

6.   Count how many insects you have. As you count, separate the different types of insects (that look different from one another) into different cubes of the ice cube tray. For example, one cube should have all the mayflies, while another should have all the stoneflies. You can use your “Biotic Index of Water Quality” to help know which insects should be together in a cube and what they are called.

7.   Next, use your Biotic Index of Water Quality chart to count the total number of insects you have that belong to “Group 1”. Fill in the number on your data sheet. Repeat this for groups 2 and 3 as well.

8.   Finally, put all the insects that belong to the same group in a vial for storage. You should have three vials when you are done.

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