I could not find information or accounts showing mothman to look like a moth. I could also find no firsthand descriptions of plumage or feathers, so I must assume that the creature is mammalian in nature.
In uncovering the physiology of mothman, we must first look at the eyes. In many accounts, they are said to be glowing red. However, all of these take place with lights shining directly at the creature’s eyes. The redness would seem to be a reflection off the retina, somewhat akin to the red-eye effect found in flash photography. Due to the massive size of these pupils, it would appear as if the mothman is almost entirely nocturnal. Excessive light, such as car headlights, would cause severe pain or even temporary blindness in such a creature.
The mothman’s eyes are set on its underside, facing the ground while flying. This would provide it the ability to detect prey on the ground (Personally, I feel it likely that the eyes can swivel forward so as to see in front, but I cannot find textual evidence of this). Its wide set eyes would provide excellent depth perception, as well as allowing it to detect potential predators easily.
In order to eat, its mouth would most likely be at the front, set between the eyes (where a normal human head would be). If this is true, then its most likely food source would be fish scooped from rivers in a manner similar to that of a pelican. However, this does not preclude it from eating land animals when necessary.
The mothman’s size would make flying impossible. However, the mothman would still be able to glide, provided that it were light enough. Due to a lack of cliffs and/or high places to jump off, I must assume that the mothman’s legs allow it to jump. If the mothman could jump high enough, this would explain both descriptions of a vertical takeoff, extended gliding, and “disappearing”. This would also mean that the mothman cannot walk in a human fashion, either giving it a penguin style waddle or the motion of a frog.
As a mammal with wings, it more than likely sleeps upside down somewhat like a bat.
And now we enter the purely theoretical territory.
Animals in the wild cannot exist alone. There must always be more of the species or it will become extinct. I believe that there was not one singular “mothman” but rather a pack/flock of mothman that descended on point pleasant.
This theory is backed up in the varying accounts of coloration in the beast. It is described variously as white, grey, black, or brown. These variations would be acceptable differences within a pack/flock, particularly if coloration changed with age.
Mothmen are also said to make a keening sound. These sounds could be calls in the same sense that a wolf howl is a call.
The pack behavior would also explain the mothmen following cars after sightings. If one member is hurt (due to excessive light) the others may attempt revenge on the “attacker”
Due to this, mothman may have developed a distrust/hatred of cars.
Mothmen likely have very little to do with the bridge collapse. The picture purportedly showing a mothman hanging off the bridge may very well have been showing a sleeping mothman moments before being rudely awakened by a collapsing bridge.
If there is any information that you would like me to go into further or if anything that I have said is untrue, please send me an ask.