Megaloprepus caerulatus

Megaloprepus caerulatus is a damselfly of the Forest Giant family (Pseudostigmatidae), found in wet and moist forests in Central and South America. It has the greatest wingspan of any living damselfly or dragonfly, up to 19 centimeters (7.5 inches) in the largest males. Its large size and the markings on its wings make it a conspicuous species; a hovering Megaloprepus has been described as a 'pulsating blue-and-white beacon'. As an adult it feeds on orb-weaver spiders in the forest understory, which it plucks from their webs. It lays its eggs in water-filled holes in trees; males defend the larger holes as breeding territories. The naiad is a top predator in its tree-hole habitat, feeding on tadpoles and aquatic insects, including the larvae of mosquito species that are vectors of human disease. M. caerulatus is the only species in genus Megaloprepus. Megaloprepus lays its eggs in the water that collects in holes in trees. These plant-borne bodies of water, known as phytotelmata, may form in a living tree when a branch breaks off or a burl rots, or indentations in a trunk may fill with water after the tree falls. The eggs hatch in a minimum of 18 days, but the hatching of eggs laid on the same day is spread out over as much as half a year. This extreme variation in hatching time—unknown in any other damselfly—increases the chance that some eggs will hatch when no predator is present. As with other damselflies, the young—known as naiads, nymphs, or larvae—are carnivorous. The most ubiquitous prey in the tree holes they inhabit are mosquito larvae, but they will also feed on tadpoles, syrphid fly and chironomid fly larvae, and other odonate (dragonfly and damselfly) naiads. The three leaflike caudal lamellae at the end of the abdomen, which serve as gills, are broad and elaborately folded, an adaptation to intermittent low oxygen availability in its habitat. Each lamella has a conspicuous white spot, making Megaloprepus easy to distinguish from other tree-hole damselflies. As many as 13 females may oviposit in a single large tree hole, laying up to 250 eggs each, but the numbers of naiads are reduced by cannibalism. Even when there is a high concentration of other prey, Megaloprepus naiads still kill each other until a density of one naiad per 1-2 liters of water is reached. They are not territorial, but larger individuals displace smaller ones; their aggressive behavior includes raising and swinging the caudal lamellae and striking with the labium, the hinged, extensible lower 'lip' that odonate naiads use to catch prey. The adult's body is dark brown or black and has yellowish markings. The wings are hyaline (transparent), with a dark blue band on the outer third. Females have a milky-tinged patch at the tip of each wing, while males of most populations have a white band just inside the blue one. In 1923, Philip Calvert described Megaloprepus in flight: