Yes, Walter, it should be a black form of the caterpillar of Agrius convolvuli: you can see six picts of A. convolvuli larvae at http://web.tiscalinet.it/leps/ (in your picture the head is not shown: A. convolvuli larva has orange, light brown or green head with (always) 4 vertical black lines). Cheers, Paolo Mazzei mazzeip at tin.it