Here's a picture (I didn't take it; it's from a website):
It's been a while since I've had the "stingin' worm" experience. Years ago, I used to get stung pretty frequently while looking at my corn patch. I could never see the bug that got me. Finally somebody told me that there were these almost invisible bugs in corn that sting very badly, called packsaddles or stinging worms.
I forgot about them, though, because for years it didn't happen to me. Then it did, today. I wonder why the stinging worms came back. Maybe it's because we've had such a wet, hot year. Today I researched the packsaddle worm online and found out that their scientific name is Acharea stimulea. Presumably "stimulea" means "it hurts."
A PBS site about American words supplied some quotations illustrating the use of the word "packsaddle," rather like the OED does:
From 1884: "I wonder if Harris ever saw a pack saddle. Well, its as putty as a rainbow, just like most all of the devil ' s contrivances, and when you crowd one of em on a fodderblade you ' d think that forty yaller jackets had stung you all in a bunch. "
From 1925 Dargan Highland Annals: "You said I must git another big mess ' fore the frost struck ' em heavy, an ' that field was plum full o ' pack-saddlers. One stung me ever ' time I laid my hand on a roas ' in ' year. Hit hurts worse ' n a hornet fer a minute, an ' it ' s harder on a body ' s temper than a hornet is."
It does hurt pretty much like a hornet for a minute, but then it stops hurting; however, the little swollen bites remain.
Anyway, if you have a corn patch, don't let little kids go in there, and if you go in yourself, wear long sleeves and/or gloves.