Male tree weta fight for ownership of a gallery in order to control access to females.  Male tree weta are frequently on the move looking for galleries housing receptive females.  If a male encounters a gallery he will enter it and attempt to pull the occupant out.  If the occupant is a female he will attempt to mate, if it is a male he will fight.  Smaller males, however, tend not to be so aggressive likely because they have smaller weaponry and are poorer fighters.  Instead, these males tend sneak into the gallery and mate inside.