Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Walking on Water
Name: star.girl
Status: student
Age: 16
Location: N/A
Country: N/A
Date: 2000-2001

Why can insects walk on water?

They are so light that they can support themselves by spreading their weight on the surface tension of the water.

J. Elliott

Some insects have a waxy coating on the body and/or feet. The surface tension of this coating [~20 to 30 ergs/cm^2] is much less than water [ 72 ergs/cm^2]. The water then tends to bond to itself rather than "wetting" the bug's feet and unless the bug it too heavy it can remain on top of the water's surface.

Ants, especially carpenter ants, are a good example of such insects. An effective safe insecticide is to surround the base of a house with a surface active agent [surfactant] that adheres to the ants feet. There are a number of non-ionic suitable waxy materials. The surfactant sticks to the ant's feet. The ant returns to the nest and further spreads the surfactant to other workers. When the ants then come into contact with water they will no longer be buoyant and will drown.

You can demonstrate this effect by sprinkling some black pepper on the surface of some pure water in a glass. The pepper floats. Add a drop of liquid dish soap to the surface and the pepper grains will rush away form the soap droplet. Stir gently once or twice and the pepper sinks.

Vince Calder

Hi Stargirl!

It is a property of liquids called surface tension that enables some insects to walk across a liquid surface, usually of a pond or lake.Also a needle can float over the surface of a glass filled with water... Surface tension is a special force that resists to be disrupted by the penetration of a needle (horizontally!) or by a water bug, for example.

These surface forces can be explained by intermolecular forces. A molecule in the center of a liquid is pulled equally in all directions by the molecules surrounding it. But if the molecule is on the surface, it is attracted by molecules at its sides and below it only. There is no corresponding upward attraction. These unequal forces tend to pull inward at the surface of the liquid and cause it to contract. That is why a drop is spherical, for example( to minimize its surface area.)

And thanks for asking NEWTON!

(Dr.Mabel Rodrigues)

Click here to return to the Zoology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory