What is a yellow jacket? A yellow jacket is an insect that has yellow and black alternating stripes on the abdomen. They are about a half an inch long and the queen yellow jacket is about three quarters of an inch long. Yellow jackets have a stinger that allows them to sting over and over unlike honey bees who can only sting once. Yellow jackets often cause people fear because of how bold they are and the fact they can sting over and over.