Seeing the spider for the eggs

Not all eggs stuck on plants are difficult to identify.  Determining what laid them is simple when the mother is still there -- as long as you notice her.

I first saw the egg sac pictured below from across the yard.  The white of the spider silk stood out brilliantly against the brown of the plant stem.  As I got closer, I could see the contours of the individual eggs neatly wrapped within the silk. 

A spider egg sac attached to a plant stem.

I wondered what kind of spider had laid them, but deciding that I wouldn't be able to identify them until they had hatched, I began to inspect the seeds on the neighboring stems.  When I looked back at the egg sac from a different angle, I was surprised to find that a rather large spider was standing guard over the eggs. 

The female spider guarding her eggs.

Of course, she had been there all along (as you may have noticed from the first picture).  I had been so focused on the bright white egg sac that I had ignored all the surrounding brown.  I was lucky that on this occasion I had decided to leave the eggs where they were.  If I had attempted to collect these eggs to raise in a jar, I might have gotten a bite instead!