As an aquatic nymph, they like to prey on insects, snails, tadpoles, small fish, and anything else they can catch.  They do this by burying themselves in sediment or mud while leaving their eyes and antennae exposed to sense nearby prey. (Needham 1955) The mandibles that are used to capture and eat prey are easily seen on this picture of an aquatic nymph.

Adult Dragonfly:
Twin-Spotted Spiketails, like other Dragonflies, love to eat mosquitoes, midges, and other small flying insects.  Adult Dragonflies are great hunters due their sharp eyesight and maneuverability.  Their compound eyes make up most of their head and they have special neck muscles that allow them to turn their head sideways 180 degrees and backwards up to 70 degrees allowing the Dragonfly to have a larger range of sight. Combined with the ability to fly 30 miles per hour, Dragonflies are excellent hunters. Dragonflies hunt while flying using their legs as a basket to catch prey. (Dragonflies 2011)