The thorax of the male is dull greenish bronze above it is a broad diagonal yellow stripe on sides.

The great spreadwing prefers slow small streams, often with alder or willows, wetlands, ponds and temporary pools.

The male great spreadwings hanging from vegetation either over or near water, usually fairly low, like under 2 feet.

On an occasion the nymphs can be spotted in winter, basking in sunwarmed shallow water alongside tadpoles.

When great spreadwings are mating and after collection of sperm, the female cuts a slit in emergent vegetation and oviposits in it.