Seeds of fear? To most of us, cantaloupe and horn melon look like a healthy breakfast or snack. But the clusters of seeds can evoke anxiety, nervousness and even nausea for some trypophobes. Daniel M. N. Turner/NPR hide caption

itoggle caption Daniel M. N. Turner/NPR

The U.S. Army distributed a monthly pinup calendar to GIs, which encouraged them to protect themselves from malaria-carrying mosquitoes. Cartoon by Frank Mack for the U.S. Army./Courtesy of the Images from the History of Medicine. hide caption

itoggle caption Cartoon by Frank Mack for the U.S. Army./Courtesy of the Images from the History of Medicine.