[4] Derived from a freshwater ancestor, the genus Megalarion consists of very diversified groups of damselflies that can grow between the lengths of 33 to 37 millimeters.

[4][5] Megalagrion xanthomelas are commonly found in calm water sources throughout Hawaii including streams and ponds and is threatened by habitat loss.

Anchialine ponds are a common habitat for Megalagrion xanthomelas to live in which requires the species to adapt to mechanisms of osmoregulation, which helps maintain their internal fluids when the surrounding salinity of the water fluctuates.

Due to adaptive radiation within Hawaiian Megalagrion damselflies, species exhibit a variety of colors ranging from blue, green, yellow, orange, and red.

[4] Megalagrion xanthomelas have red males and brown females which results in the species being named the Orangeblack Hawaiian Damselfly.

There is an exception to this dimorphic characteristic which is when the species is located at a higher elevation than normal causing both males and females to be red.

[4] This kind of natural selection was created because the red pigmentation now found in both males and females protects the Orangeblack Hawaiian Damselflies from ultraviolet damage.

After World War II, Megalagrion xanthomelas declined in numbers over the years and is no longer present within the inlet of Pearl Harbor.

[7] Anchialine ponds are the most common habitat for Megalagrion xanthomelas since this type of water source is found in low-lying areas within the Hawaiian Islands.

[5] After the life cycle is completed, the adult stage of Megalagrion xanthomelas can decide on looking for another habitat to reproduce in or staying near the water source itself emerged from.

Megalagrion xanthomelas used to be so abundant back in the 1800s, that fields and any shallow water source would be swarmed with Orangeblack Hawaiian Damselflies.

The resulting impact of all this construction would lead to the elimination of any remaining populations of Megalagrion xanthomelas and an increase in the salinity level within the inlet.

[5][6] The introduction of invasive species has been a major threat to most aquatic habitats within the Hawaiian Islands and has been the main cause of the decline in population numbers for Megalagrion xanthomelas.

[7] Comparative studies between the responses of younger and older life stages to the salinity level of the water source can help determine what information is needed to increase their survival rate within their habitat.

[5] Focus primarily on the naiad since that stage of the life cycle is completed in the water and has no way to osmoregulate or protect itself from the high salinity levels that might occur within its habitat.

[5] The habitat for Megalagrion xanthomelas is commonly anchialine ponds that are very susceptible to pollution, degradation, alteration, and the introduction of invasive species.

The habitat for Megalagrion xanthomelas could be contaminated by pollutants due to sediment being pushed into water sources around construction sites and roads.