The third picture down in Mozz's post (http://nepacrossroads.com/about17324.html
) is the HIckory Tussock Moth Caterpillar.
They secrete and acid/poison from their feet that some people have very bad allergic reactions to.
As a young chap of 17, I was mowing lawn for a living in a willow grove when one, apparently, fell on me. I was wearing an old button up shirt, half unbuttoned at the top, and when I noticed the little guy he was on my chest. I flicked him off, kept mowing, until my throat started to feel funny. I looked down and my chest was fire read and swollen. With no benadryl on me I rushed home and popped 2 busted open under my tongue so they'd go right to the blood steam (I have a bee allergy, so this was standard procedure). No good - too much caterpillar, or too much time - my throat was swelling shut - I couldn't swallow and it was getting hard to breathe. My mother called 9-1-1 and I took a ride in the ambluance with an oxygen tube shoved down my restricted air way. They injected me with some "super benadryl" and I slept for 8 hours in the middle of the day!
You can imagine my delight, years later, when I come home from work to my 3 year old boy who is holding one of these in his hands. "Daddy, daddy, look what I found!". I smacked it out of his hands and ground it into the concrete sidewalk. He was devistated! I dropped my stuff and marched him in the house - stripped him down - and started washing him off in our downstairs bath. He was screaming profusely from this treatment and my wife - who had not know of the circumstances came running in to see here husband still dressed nice for work scrubbing a kid down at 5:30pm in the afternoon. I had her get a double dose of childrens benadryl out for him and of course he screamed for all of that! In the end - his one leg swelled up almost 50% over it's normal size for several hours, and he had "scratch" marks (where the caterpillars feet walked) all up and down his arms.
Now bad genetics may make us the exception to rule here - as I know several people who can pick these up and hold them with no problems - but I would at least advise extreme caution.
The HIckory Tussock Moth Caterpillar is not welcome on my property. We have a bounty on it's head (or tail or abdomen or what ever caterpillars have!) - they are to be shot on site!