The dragonfly nymph ( Odonata , Anisoptera) are very common in areas of standing water with aquatic vegetation and have an important role in the diet of trout in those places. They are very common , but not usually found in boxes of fishermen , often ignored or minimized. Insects are a good size , usually measured 2-4 cm . Because of its significant size , in my experience this nymph imitations require a higher level of realism that imitations of small organisms.