There are about 5000 types of dragonflies. Dragonflies eat other flying insects. They also will take butterflies, moths and smaller dragonflies. Most temperate-zone species live as adults less than a month, though some type can live up to six months. Birds, spiders, frog and larger dragonflies eat dragonflies. It is predicted that the speed for an average dragonfly is between 30 and 60 km/h. The maximum speed differs a lot between different species, but bigger dragonflies fly faster than smaller ones. They flap their wings about 30 times per second. However, dragonflies have two sets of wings, so they don't have to beat very fast. A dragonfly can see all the way around itself, because its eyes have about 30,000 lenses. Although, the human eye with only one lens humans can see more sharply even though its only through the front. Dragonflies are really known for their speed. Dragonflies can move frontward at a rate of 100 times their body span each second, at times they can reach speeds around 55 miles per hour. They can also move in different directions. They can move backward, sideways and on a diagonal. Their speed and agility mean they can quickly zoom away from and outmaneuver any potential predators. It gives them an advantage when hunting for food.