Patrolling male dragonflies can be very hard to net, especially emeralds. They are very alert and fast, and typically don't allow close approach. However, they are very territorial, so when another dragon enters their airspace they will chase after it like a Sidewinder missile. When they are thus distracted, they don't really pay attention to where they are flying. These two males were involved in a chase when they zipped right into my waiting net.