3 ms·

Well the article claims cave is pitch dark, so I guess the invisible part is granted anyway.

• kijin 10mo ago
  Cave-dwelling animals don't just crash into walls all the time, so by "visible" I mean large enough and dense enough to be recognized as an obstacle in whatever navigation system they use.
  • hnlmorg 10mo ago
    They do rest on walls though.
    • thaumasiotes 10mo ago
      In this case every part of the wall is actually just a spiderweb.