  The stability of pasta phases in cylindrical and spherical Wigner-Seitz (W-S)
cells is examined. The electric Bond number is introduced as the ratio of
electric and surface energies. In the case of a charged rod in vacuum, other
kinds of instabilities appear in addition to the well known Plateau- Rayleigh
mode. For the case of a rod confined in a W-S cell the variety of unstable
modes is reduced. It comes from the virial theorem, which bounds the value of
the Bond number from above and reduces the role played by electric forces. A
similar analysis is done for the spherical W-S cell, where it appears that the
inclusion of the virial theorem stabilizes all of the modes.
