Who is Mothra?

Unless you are referring to the Japanese movie monster with a cult-following(in which case, you are on the wrong site), Mothra is the name given to protect the identity of a woman that Russ took out a couple of times.

After inviting herself to spend the night for an additional night, bringing her dog to Russ' house and allowing it to run rampant, spending the entire night of one of their dates complaining(mostly about not being the center of attention) Russ told her to leave. His words were direct, simple, and to the point. She wanted to "talk about it", but Russ didn't, so Russ asked her to just go on and get into her car. Russ went back inside and left to ride his motorcycle. He came back to find that this psychopath had pulled his flowers up from his yard, tossed said flowers into neighbors' yards, ran her car into his garage door, damaging it severely enough to warrant replacement, jerked his alarm company sign out of the ground and used it to beat repeatedly on his wooden front door, putting deep gouges in it.

Russ was lenient, declining to press charges, and accepting a fraction of the cost of repairing the damage she did as recompense.