Mosquitoes have a life cycle that is dependent on the presence of standing water. They do not need a lot of it but they definitely need a source of water for them to breed and for their offspring to reach adulthood. These sources of water can be anything from birdbaths, tires, buckets, wheelbarrows, gutters, broken bamboo shoots or even hollows in trees. If you are seeing an abundance of these insects in your yard, you should first check for one of the aforementioned or other possible sources of stagnant water. Mosquitoes are also strong fliers and can travel up to three miles in search of a blood meal so while the problem is likely local, it could be originating from outside of your property.