(The Dance of the Water Strider)

Background: Water has more surface tension than any other liquid with the exception of mercury. The surface tension forms an "elastic film" on the surface of the water. Insects such as water striders can walk on water because of the surface tension and their unique anatomy. Water striders are a true bugs belonging to the order, hemiptera. They can be found skimming or "skating" over the surface of quiet protected water in ponds and lakes. They also can live in quiet backwaters or gentle flowing waters in streams. Water striders are predaceous (hunt for food). They use specialized mouth parts for piercing and sucking the contents of their prey. Generally, prey are aquatic insects which are caught just below the water surface or on the water surface. Adults communicate by moving their front legs to vibrate the water surface with certain frequencies.

The challenge: Working with your cooperative team, design a bug that can walk on water. The specifications for the bug are as follows:

•The bug must have six legs and two antenna.

•The bug must fit into a 20 x 30 cm container

•The antenna cannot be loner than 8 cm (from attachment to head to outer most extension.

•The legs cannot be longer than 10 cm, from attachment to body to outer most extension.

Suggested materials: styrofoam, plastic bottles, straws, glue, hot glue, candle wax, garbage bag ties, toothpicks, pipe cleaners, thin wire, popsicle sticks, oil or grease.

Background Research: This is information you should know before you begin the planning of your insect’s design and construction. The answers to these questions should be included in the write up of this activity.

• What is the density of water at 4°C?

•What is Archimedes Principle of Buoyancy?

•What other information might be helpful before you begin your design of the water slider?

Sketch your water strider in the box below.

Attach to this activity a paper that includes the following information:

1. Answers to Background Research questions.

2. Procedure Followed: List all supplies and write the procedure you followed in the construction of your bug. Make sure to include all size specifications that you used.

3. Results: Record the success or failure of your bug to "walk" on water. Include the density of the insect as it compares to the density of water and any other relevant observations.

4. Conclusions: In your discussion make sure to answer the following questions: