The main difference is in size, though there are differences in coloration.Asian giant hornets are about 2 inches long, and they have a yellow head with yellow and black or yellow and brown stripes on their abdomen. Cicada killers are usually 1.5 inches long, and they are black or dark brown with yellow stripes and a dark-colored head. Cicada killers are solitary.European hornets are between 3/4 and 1.5 inches long. They are usually brown with yellow stripes and pale colors on their heads.