Some websites design and sell some water bags for repelling flies. However, the effectiveness of this method is a vexed question. Experts themselves don’t still unified their views.

Those using this method said that flies may confuse these water as a wide area. Others said that flies will fly away because their shadows are zoomed when seeing the water bags. However, the reason which most entomologist and enterprises producing these water bags consider that flies are fear light refraction.

Refraction occurs when a pure or troubled object like a glass fragment or a water bag change the vector and speed of light. The light rays are bend. This quality is applied in some sight phantom.
In theory, light refraction can make some insects, especially fly confused. Light refraction strongly impact on fly sight because their eyes can see everywhere in the same time.

Their eyes make up a large portion of fly’s head area. Each eye is composed of 3000 – 6000 smaller eyes. These eyes cannot move or concentrate on a fixed object like people’s eyes. Fly eyes allow them observe the whole view in the same time. Each small eye can see a part of the object as each pixel of camera can catch an image point.

Direction feeling of flies is based on light vector. Some researcher said that their sensitive and complex eyes suffer from light refraction which was caused by water bags and make them embarrassed.

Some protesters considered that this method is just a spiritual medicine helping people peace of mind. Professor of entomology – Mr. Mike Stringham from the North California has conducted an experiment to check the effectiveness of this method lasting 13 weeks with two farm laying hen farms.

He estimated fly activities based on residuals after they eat and fly away. As a result, fly activities in water bag areas are higher than others.

However, the research did not conduct in natural light. The aim of this research is proving the effectiveness of water bags but it does not estimate the role of light in water bags.