mosquitoes hide in the shade during the day when its hot. They are more active early in the morning and evenings when its cooler. They usually go on "searching" flights in the evening and night for blood sources. That is where dark shade comes into play. To the person with the skeet-r-done product that probably works for the company: It won't work. Use a product with DEET it is the most effective and it won't hurt you. The other products that have "natural" items like citronella in them aren't effective more than 10-15 mins.