  We study the effects of vertical sinusoidal vibrations on a liquid droplet
with a low surface tension (ethanol) deposited on a solid substrate. In a
precise range of amplitudes and frequencies, the drop exhibits a dramatic
worm-like shape instability with a strong symmetry breaking, comparable to the
one observed by Pucci et al. (Phys. Rev. Lett., 106 (2011) 024503) on a
vibrated floating lens. However, the geometry of our system is much simpler
since it does not involve the oscillation and deformation of a
liquid-liquid-air contact line. We show that the Faraday waves appearing on the
surface of the droplet control its shape and we draw a systematic phase diagram
of the instability. A simple theoretical model allows us to derive a relation
between the elongation of the droplet and the amplitude of the Faraday wave, in
good agreement with measurements of both quantities.
