  We present an experimental investigation of collective behavior of the
swimming nematode Turbatrix aceti, commonly known as the vinegar eel. When
placed in a droplet at high concentration, these worms self-assemble in a
striking collectively moving traveling or metachronal wave. The flows produced
by this state are strong enough to visibly deform the surface of the droplet
and induce rotational fluid flows. We show that the contact angle of the
droplet is the parameter controlling the transition from random motion to the
collective metachronal wave sate. Finally, we find that the collective motion
of the nematodes changes the physics of droplet evaporation from one at
constant contact angle to one at a constant surface area. The mm size and ease
of culture make Turbatrix aceti a promising model organism for experimental
investigation of motile and oscillating active matter at the mesoscale where
the Reynolds number is of order unity.
