Hi: I remember when I was in college working on my degree in Biology, I was given a choice as to creating new life with flies or making a disease resistant to an antibotic. Of course I choose to make a disease resistant to an antibootic, but I also studied the creation of new life with the flies and its larve. Needless to say, I still have some information on that subject in the form of a research article and I believe that after reading this article, then you will be enlightened to create your own theories on this subject of: How does a plastic bag filled with water act as a fly repellent. What does the fly really see? Jul 1, 2003 By: Dr. Moray Anderson Pest Management Professional Customers are always coming up with questions about pests that could stump even your most knowledgeable technician. Flies are a popular subject, because they are usually quite visible at an account. For example, have you ever been asked how the eye of the fly "traps" light? Light is captured in the eyes of insects by structures called ommatidia. Each adult housefly, for example, has about 3,000 ommatidia in each eye. The outermost section of them can be seen in the eyes of the housefly as hexagonal patterns. In each of these 3,000 ommatidia, there are eight sensory cells (R1-R8). Each contains photopigment, which responds to particular wavelengths of light. In most insects, the regions of the cells that contain the photopigments are fused - and all the cells sample the same point of light. However, in flies there is a remarkable and unique modification. Each of the light trapping zones in the sensory cells is separated from its immediate neighbors. The clever trick is that light from any point is collected by six different ommatidia, and therefore the intensity of the image on the retina is greatly enhanced. This makes the vision of the flies much more sophisticated than that of almost any other insect. Response to UV light Flies' eyes are also very special in their response to ultraviolet light. The sensory cells mentioned above (R1 to R8) each have different sensitivities to the various parts of the color spectrum. Cells R1 to R6 are particularly sensitive to UV light. These cells have a secondary and unique photopigment that reacts to the light in the UV range (300 to 400 nm). Within the eyes of flies, there are a couple other unique features: Girl goggles - In male flies, there is a special zone in the front of the eye (the two eyes have their greatest area of binocular overlap here) where the cells have lost their ability to see color. These spots are specially developed so that the males can detect female flies in flight in the immediate vicinity. Polarized light detection - This ability is concentrated in certain zones of the eye, particularly around the margins. The cells that are sensitive to polarized light are also highly sensitive to UV light, and are thought to be navigational aids. These physiological processes only reveal what the fly's eye is able to detect. It is possible to show by electrical recordings what regions of the eye are sensitive to what wavelengths. It is only by elaborate and detailed behavioral experiments that we are able to get clues as to what the fly sees. The brain of the fly is highly evolved to processing visual information, with about 70% devoted to visual processing. Each fly species has different visual sensitivity that changes according to the sex of the fly, its age, its feeding status, its reproductive stage, etc. Not only will this knowledge dazzle your customers, it can be helpful when explaining how effective your insect light trap can be at the account. Dr. Moray Anderson is technical director of the Killgerm Group, West Yorkshire, UK, and is considered an expert in public health as it relates to flying pests. Contact him at pccontributor@advanstar.com