The egg snatchers

Summer is ending and there are fewer flowers blooming in the garden.  As a result, the foliage gets more of my attention.  It may not be changing color yet, but it is covered with insect and spider life.  Earlier this week, I noticed several clusters of small eggs on lamb's ear (Stachys byzantina) leaves and on grass.

I was curious to know what had laid all these eggs.  Although most of them had already hatched, I did not see any insects nearby nor any damage to the leaves from hungry young insects.  Therefore, when I found a cluster with about half the eggs still unhatched, I decided to keep the eggs in a jar and observe what emerged. 

The leaf and eggs in my "incubation chamber": a jam jar with a damp paper towel.

The next morning, I saw my first hatchling -- but it was not the offspring of whatever had laid the cluster of eggs.  Instead, it was a parasitoid wasp.  Some time ago, this wasp must have hatched from an egg laid inside one of the already small eggs visible in the picture below.  It then grew, consuming the insect that was developing in the surrounding host egg. 

A parasitoid wasp emerged from one of the eggs.

Two more days have passed and the first wasp has been joined by several more wasps.  Nearly all the eggs have hatched, but I am no closer to finding out what laid them!