Frank takes his 1-year-old son Jaleel out for a walk. Jaleel reaches over to touch a red flower and is stung by a bumblebee sitting on the petals. The next day, Jaleel's mother brings home some red flowers. She removes a flower from the arrangement and takes it over for her baby to smell. Jaleel cries loudly as soon as he sees it. According to the principles of classical conditioning, what is the unconditioned stimulus in this example?