The Screwworm, Cochliomyia hominivorax (man-eater) was endemic to Texas and the Southwest, but I can’t find much about them until the late 19th Century. [The 1858 Devil’s Island prison off the coast of French Guiana, was the site of the first recorded screwworm epidemic] The fly lays eggs next to a wound of any warm-blooded mammal, after 12-24 hours the larvae hatch and crawl into the wound and feed on living flesh. Killing the animal in five to ten days. It is supposed that the screwworm fly migrated northward because of warming climate. Cattlemen had to use much of their time riding the range looking for “wormies.” In 1888, a man named George Whitefield complained of horrible headaches, when he went to the door to blow his nose, out came five large screwworms. He died an hour later. (September, Stephenville Empire) A government sterile screwworm fly program ended U.S. infestation in 1966, global warming still encouraging them to migrate northward. The USDA maintains an international screwworm barrier along the Panama-Columbia border, dropping sterile flys each week and patrolling the area constantly. An infestation slipped northward in 2016 and showed up in Florida among the deer population, but quick action by the sterile program stopped them that same year.
Mackenzie Tietjen, et. al. “Geographic Population Genetic Structure of the New World Screwworm, Cochliomyia hominivorax (Diptera: Calliphoridae), Using SNPs.” Journal of Medical Entomology, Volume 59, Issue 3, May 2022; and A.P. Gutierrez and Ponii Arias. “Deconstructing the Eradication of New World Screwworm in North America: Retrospective Analysis and Climate Warming Effects.” Medical and Veterinary Entomology, Volume 33, Issue 2, 2019