Trego's Mountain Ear

The United States eradicated the New World Screwworm back when I was in high school. I’m reading about a guy in Maryland diagnosed with screwworm infection – but he had been in Honduras before the diagnosis. According to Scientific American https://www.scientificamerican.com/article/flesh-eating-screwworm-parasites-are-headed-to-the-u-s/ “The pest is marching northward at an alarming rate and has now moved some 1,400 miles from southern Panama to southern Mexico in about two years. Screwworms are disastrous for ranchers, whose cattle can become infected when the flies lay eggs in cuts or wounds, after which their resulting larvae burrow, or screw, into that flesh. The northernmost sighting is currently about 700 miles south of the U.S. border. ” For years, the NW Screwworm has been controlled by releasing batches of sterile male flies into the Darien Gap region – but that technique and location is no longer adequate. “That invisible wall holding the screwworm back has crumbled, however. “I don’t know how it got away so quickly,” says Maxwell Scott, an entomologist at North Carolina State University, who studies genetic methods to control populations of the fly. “There had to be some movement of infested livestock, particularly through the middle [of Central America]…. It just moved too fast,” Scott says about the swift speed of the screwworm spread. “

I’m not particularly concerned about screwworms, since I live just below the 49th Parallel – but this old map does a fairly nice job of showing where the damned things could overwinter in 1952 – and the line correlates with a combination of altitude and latitude. In other words, our dates of first and last frosts may also show where the screwworm can overwinter.

Pesky Little Critters https://peskylittlecritters.com/how-climate-change-influences-the-distribution-of-screwworm-flies/ concludes their article with “Climate change is reshaping ecosystems worldwide—including those influencing pest species like screwworm flies. Through rising temperatures, shifting humidity patterns, altered host distributions, and more frequent extreme weather events, the range and population dynamics of screwworms are changing.”

It’s not a huge drama – but it is interesting that the actual effects of global warming may first be measurable in insect ranges.