Mosquitoes need water to reproduce, and they find water in various places such as:
pots & planters
grills and tarps
This is why removing standing water is your first defense against these pests. During the day, mosquitoes also seek shelter from the sun and become more active in cooler evening air or in shady areas of your yard. Female mosquitoes lay their eggs on the surface of the water — the eggs feed on bacteria in the water.
Know the enemy.
Bug zappers and ultrasonic pest devices are both commonly-used control devices, but they are ineffective and a waste of money. While bug zappers do electrocute some female mosquitoes that get in contact with these products, the majority of bugs attracted and killed by zappers are moths, beetles and other beneficial insects. This reduces the food population for songbirds and other small animals that depend on these insects to thrive.
Several studies over the past few years have proven ultrasonic pest control devices as ineffective in repelling insects, including mosquitoes. They are sold as environmentally-friendly methods of mosquito control that are supposed to work by interfering with the wing beat frequency used by mosquitoes to find mates in swarms. These devices are sold as electronic mosquito repellents, or EMRs, but they ultimately won’t repel mosquitoes the way you want them to.
What doesn't work
Complete mosquito development from egg to adult can vary by temperature, but it generally takes between 10 to 14 days. Females lay hundreds of eggs, which hatch within 48 hours, and adults begin breeding within 2 days after emerging. This results in mosquito populations that increase quickly in favorable conditions.