The insects are in a large group on the underside of a cornus florida branch. They resemble black ants, but their abdomens are a bright orangish-red, & their legs are long & bend up first, then down, so that part of the leg is above the body. The abdomen is tipped up at the back. They're building an octogon- or hexagon-shaped group of "cells" on the tree...

I have searched online & in books & can't find them. What are they?

Thanks!

http://www.floridanature.org/photos/Arilus_cristatus,_Tallahassee,_20020504.jpg

My friend was lucky enough to have one in her garden, It was black with red and black body. They rear up their hind end when approached.
If this is what you have they are beneficial and good to have around ..
I had an adult last fall in my house and set him/her loose in my garden. Later I found an instar on my palm while taking it in for the winter.

Thanks so much for leading me there, seventowers.

ferncreek