The Moth was a regular moth which accidentally became exposed to the t-Virus
for an extended period of time which mutated it in a rather unexpected way: It grew in size perfectly proportionally so it could fly as gracefully as an uninfected moth which is quite the opposite to what happened when Umbrella tried to specifically engineer a B.O.W. (Bio-Organic Weapon) based on a moth named the Giant Moth
As this creature was essentially created accidentally and in one place only, Umbrella did not officially recognise it as a B.O.W.
They were highly poisonous due to their infection and could emit a dust cloud which when inhaled could injure the persons lungs and poison their body. The moth could also scatter clutches of eggs in damp corners or along the edges of walls similar to fleas and other insects.
When these eggs hatched, parasitic larvae would spring from their eggs and attack any nearby target, poisoning them. The Moth was also agile enough to plant an egg directly on a person which would hatch after a few moments.
As the Moth was created accidentally due to a t-Virus
outbreak on a remote Umbrella base in Antarctica, the Moth had no chance of spreading to other continents and therefore lived and died there. It’s now considered to be an extinct species, although it could be entirely possible that an egg may still be in tact due to the extreme cold there.
No attempts were ever made to re-create the Moth in lab conditions, so it is assumed that nothing was learned from their existence.