I'm totally disappointed...
Thanks to everybody who responded:
"sci.bio.entomology.misc",
"sci.bio.microbiology",
"alt.home.repair".

A camera flash at the proper angle,
then enhancing the contrast
(just to make sure)
showed that all
was just ...


... some glue-like stuff on the wall that was
causing paper and other junk
(blown by the AC)
to stick.
:-(