Squid Seven wrote in
:

I saw pictures about a decade ago of cacti covered in bright
patterns. I thought I remembered the caption of these pictures
indicating that these were photographs taken using film sensitive
to frequencies either slightly higher or slightly lower than what
humans can see - but frequencies that are visible to many
nocturnal pollinators. Recently I was reminded of this vague
memory, and tried to find relevant info on the web. I can't! Am
I misremembering something, or was I possibly hoaxed? The
pictures were on the pages of a book I randomly pulled off the
shelf in a bookstore. It seems to me like a not unrealistic
evolutionary advantage - what we see as green cacti their
nighttime pollinators see in shades and patterns intended to
attract and guide to flowers.

Can anybody help me out here? I did find refs regarding the
colors of cacti flowers being those most visible at night, but
nothing regarding uv or infrared. And which of those would be
more advantageous for critters using moonlight and starlight? My
instinct says UV, but it's been a decade since I had physics
101...

Thanks from a well-rounded amateur!





A lot of flowers have lines that show up in UV but not in visible
light. Lines such as those wouldn't be much help for night
pollinated flowers, as there isn't a whole lot of UV light after the
sun goes down. You would need Infra Red light for night time
viewing. Most cactus flowers where I live (New Mexico) close up at
night and reopen in the morning, the few that open at night are
white, which is the color that would be most visible at night.

Sean