Water Striders

Curriculum Fit

As presented, this activity fits

With modifications for topic and students' skill levels, this activity would also fit

Connection to other curriculum areas can be incorporated

Students will observe a water strider to discover

Late spring through to early fall

20 - 30 minutes

Review the concepts of interdependency, adaptations and ecosystems.

One pail and one magnifying glass per student or small group

Wetlands - slow moving or still water

Water striders are usually present in large numbers in an area so they are easy to spot.
- Have students look for water striders moving about on the surface.
- If no water striders are seen within a few minutes, move the group to another area.

Have the students crouch down and watch the water striders.
- Are the striders on the water surface or in the water? (Answer - on the surface.)
- Can you see the water strider's shadow on the wetlands bottom? If so, looking at the shadow, what seems to be at the ends of the legs? (Answer - small bumps that may appear to be feet are actually tiny dents in the film of the water surface.)
- Do any of the striders appear to be eating? What do you think they eat? (Answer - small insects that either swim up to the surface or fall into the water.)

Ask your group to watch carefully (water striders move very quickly) as you
- Pick up a tiny piece of DEAD material from the ground. Drop it onto the water surface. How do the water striders react? (Answer - the water striders detect the slightest water movement through sensory organs in their legs. If the object is small and light, the striders may approach it, thinking it is an insect. If the object is heavier, they flee, fearing a predator.)
- Put your hand in the water and move it about. How do the striders react? Large water ripples may mean a big predator is nearby.
- If there are striders close to the edge, move your arm above them. How do they react to a possible threat from above? Do they move away quickly or stay very still?

Scoop up a water strider and some water in a pail. Have each student use a magnifying glass to look for these physical characteristics and special adaptations.
- Water striders are insects. Insects have three body parts, six legs and a pair of antennae.
- Front legs are short - used for grasping prey.
- Middle legs are long - used for "rowing".
- Back legs are long - used for "steering".
- Middle and back legs can be used for quick jumps to catch prey.
- Striders' claws are set up higher on their legs than other insects. This is so the claws do not pierce the film of water surface tension.
- All legs are covered with water resistant hairs. These trap air to help the strider walk on the water surface.
- Wide spread legs distribute the strider's weight over a large area. This also helps the strider walk on the water.
If you are unable to catch one, discuss the above features as students watch the striders moving around.
RELEASE THE WATER STRIDER BACK to the wetlands.