One interesting family that is found only in the Neotropics, from Mexico southward, is the Helicopter Damselfly family (Pseudostigmatidae). These are very large damsels, with drab bodies but a prominent spot of color on the wing tips. They are found even in the darkest rainforests, and seem almost ghostly as they move slowly in an unusual whirring flight.
Morphologically the family is noted for having a multi-celled pterostigma, and behaviorally for their unusual prey specialization: they pluck spiders from webs. Also interesting is their life history: the helicopter damselflies whose life histories are known spend their larval life in water in tree holes and in the “water tanks” formed by bromeliads.
Recent research suggests that family Pseudostigmatidae should be merged into Coenagrionidae.