Water Striders
Self-Guided Activities | Sense: Smell | Beaver In Fall | Ground Squirrels | Fungi |
Weather and Climate Scavenger Hunt | Interdependency Inventory

Introduction:
As presented, the following activity is designed to fit the grade 2 unit "Small Crawling and Flying Animals". With modifications to fit topic and students' skill levels, it would also work well for the grade 1 unit "Needs of Plants and Animals" (#1, 6 and 10), the grade 3 "Animal Life Cycles" (# 4, 6 and 7), and grade 5 "Wetlands" (#2, 3 and 4). Connections to other curriculum areas can be incorporated: math (measuring, calculations), art (sketching viewpoints and by direct observation, rubbings) and language arts (journals, reflection, poetry), drama (skits, charades, role playing), social studies (map reading, communities).

Activity Summary:

Season: Late spring through to early fall

Time: 20 - 30 minutes

Preparatory: Review the concepts of interdependency, adaptations and ecosystems.

Equipment required: 1 pail and 1 magnifying glass per student or per small group

Setting: Wetlands: slow moving or still water

Instructions:

1. Have the students look for water striders moving about on the surface. If none are sighted within a few minutes, move your group to another area of the wetlands. Water striders, usually present in large numbers, are easy to spot if they are in an area.
2. Crouch down and watch the water striders. Ask the students while they are observing:
• Are the water striders on the water surface or in the water? (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? (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? (small insects that either swim up to the surface or fall into the water)
3. When your group has finished the general observations, ask them to watch carefully (water striders move very quickly) as you do the following:
• Pick up a tiny piece of DEAD material from the ground and drop it onto the water surface. How did the water striders react? (The water striders will detect the slightest water movement through sensory organs in their legs. If the object you dropped was very small and light, the striders may approach it, thinking it was an insect. If the object was heavier, they will flee, fearing a predator.)
• Put your hand in the water and move it about. How did the striders react to the large water ripples that may mean a large predator is nearby?
• If there are striders close to the edge, move your arm above them. How did they react to a possible threat from above: move away quickly or did they stay very still.
4. Use the pail to try to scoop up a water strider and some water. If you catch one, have each student use the magnifying glass to look for the following physical characteristics and special adaptations. If you cannot catch one, discuss these features as the students watch the striders moving around.
• Water striders are insects. Can the students see the body has 3 parts, there are 6 legs and there is a pair of antennae?
• Front legs are short; they are used for grasping prey.
• Middle legs are long; they are used for "rowing".
• Back legs are long; they are used for "steering".
• Middle and back legs are usable for quick jumps to catch prey.
• All claws are set up higher on the legs than other insects so the claws do not pierce the film of water surface tension.
• All legs are covered with water resistant hairs that trap air to help the strider walk on the water surface
• Wide spread legs distribute the strider's weight over a large area, helping the strider walk on the water.
5. RELEASE THE WATER STRIDER back into the wetlands.
6. Discuss the relationship water striders have with other living and non-living parts of their environment. 
• Living: water striders eat small insects on the water surface. They are eaten by some species of larger insects, fish and water birds. Water striders DO NOT bite people.
• Non-living: water striders may burrow into mud or under stones during the winter or if the water dries up temporarily. They may also overwinter under fallen leaves on land near the water. Water striders cement their eggs onto floating objects just under the water surface.