There are likely so many dragonflies in the yard because it provides an ideal habitat with plenty of water and food. Dragonflies spend their early life underwater as nymphs, so yards with ponds, birdbaths, fountains, or nearby natural water sources attract them for mating and laying eggs. Additionally, dragonflies feed on many small insects like mosquitoes, gnats, flies, ants, and termites, so a yard with an abundance of these insects acts as a magnet for dragonflies. Dragonfly swarms can also appear due to mass hatching and maturation cycles, seasonal insect hatches, or migratory behavior when dragonflies stop to rest and feed during migration. Warm weather, heavy rains, and disturbed insect colonies can cause spikes in prey availability, leading to large numbers of dragonflies gathering in one place. Their presence is actually beneficial because they are natural pest controllers that help reduce populations of mosquitoes and other small pests.