The Pillbug may not move the piece most recently moved by the opponent.
The Pillbug may not move any piece in a stack of pieces.
The Pillbug may not move a piece if it splits the hive (violating the One Hive Rule).
The Pillbug may not move a piece through a too-narrow gap of stacked pieces (violating the Freedom to Move Rule).
Any piece which physically moved (directly or by the pillbug) is rendered immobile on the next player's turn; it cannot move or be moved, nor use its special ability. The mosquito can mimic either the movement or special ability of the pillbug, even when the pillbug it is touching has been rendered immobile by another pillbug.