Parchment worms are best pinched in the dark

Tube-dwellers make a mysterious glowing mucus

GLOW WORM  Parchment worms use their filmy flaps to pump water through the tubes they build around themselves. This one has been removed from its U-shaped home.

D. Deheyn/Scripps Inst. of Oceanography, UCSD

Oh go ahead. Squeeze the soft tube of a parchment worm.