"Bathroom Etiquette" for Crab Spiders

Okay, forgive me for this one - but I had never seen it before and I find it interesting, despite feeling like a 3rd grader as I share it.

Yesterday I took a lot of photos of the insects that were visiting my Echinacea, since they're in full bloom and not much else is going on right now.  As I photographed, I kept an eye on this little crab spider, wondering what it was going to capture, if anything.  Multiple skippers and small butterflies visited the flower it was guarding, but I didn't see it attack anything, although it was obviously in hunting position.

Shortly after I took this picture, I noticed the spider move.  It seemed to be changing positions to the other side of the flower, so I snapped a quick photo.

Right after I snapped the photo, the spider quickly deposited a drop of white liquid that fell onto the petal below it...

...and then started moving right back to its original position.  Spider urine?  Spider feces?  Byproduct of some sort?  I have no idea.

The crab spider went back to almost exactly the same spot it had been settled into a few moments before and resumed its hunting posture.  The entire "adjustment" took just a few seconds.

Six minutes later, the crab spider was still in its hunting posture in its favored location on the bloom...but the drop of white liquid had disappeared.  Evaporation?  Something had lapped it up and I somehow missed it?  I was still in the same spot, photographing other insects on other blooms. The liquid fell off the petal? I don't think that last possibility occurred, because there was nothing on the leaf below, which the white drop would have had to land on.

A tiny bit of ordinary life observed.   A tiny mystery remaining.  What tiny, extraordinary ordinariness have you observed in your garden lately?