This critter was found by Bentsen-RGV SP naturalist Jim Booker, who noted it as all dark and dramatically smaller than our usual wasp-moth Horama panthalon. He convinced Ellie Thompson to photograph it. Charlie Sassine ID'd it from the photo as probably H. americana. I see that all three Harrisina species occur in Texas, and two of the three can appear as all dark without the orange collar. The most likely host plant here is Cissus incisa, which also happens to be the host of our local Vine Sphinx (Eumorpha vitis) caterpillars.