Cuckoo Wasp - Chrysis sp.
Order Hymenoptera / Suborder Apocrita / Superfamily Bethyloidea / Family Chrysididae -- cuckoo wasps
Live adult female wasp photographed at Winfield, Illinois
Size: 15mm

Cuckoo wasps roll into a tight ball when disturbed or attacked. Many are parasitic on bee or wasp larvae, some attack Symphyta larvae and one attacks Phasmid eggs. Most occur in woodlands. I found this single specimen rummaging around in the holes of a dead tree where ichneumon wasps were having a field day, too. I'll apologize for the poor quality of these pictures - this wasp was very shy and wary.