Taming of the Screw, Act Two

In our last piece, you learned about a plain-looking bug that produces some very aggressive babies, a character that has made many headlines in the last few months as it eyes its old stomping grounds in the U.S.. In 1935, the New World Screwworm had our agricultural economy in the palm of its hand. By 1966, it was clearly the underdog; by 2006 it had fully surrendered and fled back to South America (exception: Cuba, Haiti, and Dominican Republic). Amazingly, this feat was accomplished without a single drop of pesticide.

It was achieved by turning the screwworm’s own way of life against it. Here’s how: screwworm flies are totally harmless until they start to lay eggs. If they were somehow rendered infertile, their eggs would never hatch into that carnivorous 10-millimeter monster that can annihilate entire herds of cattle. Since the female of this species can only breed one time, scientists believed that presenting them with an abundance of infertile, decoy males would render most of their eggs useless. It worked fantastically well. This truly elegant plan was eventually burdened with a relatively awkward name, “The Sterile Insect Technique”. It’s approaching 70 years old now and is still being used.

The Sterile Insect Technique employs very precise radiation exposure to produce flies that can perform every single fly duty, including the act of breeding, except the successful hatching of the offspring. Maggots had to be purpose-bred for this, of course, and the maggots were appallingly greedy. A facility was built in Mission, TX to house the operation, and its initial maggot diet required enormous, unthinkable amounts of meat and blood harvested from the very cattle they were trying to save. That recipe was eventually modified to include just milk, egg protein, and blood mixed with recycled newspaper. Much more affordable than meat. Sterilized insects could be produced in quantities of 500 million a week; they were then released in small cardboard boxes spewed out of airplanes. What a scheme!

The screwworm was expelled from the U.S. by 1966 using that ambitious game plan, but the border was just too long to protect indefinitely. It would be far more efficient to locate the center of operations farther south, where the land mass is narrower. And this is the fairy tale part of the story: back in the day, the U.S. was happy to cooperate with other countries in order to reach a common goal. Through friendly collaboration with Mexico and the seven countries south of it, the center of NWS operations was moved farther and farther south until it settled in the southernmost tip of Panama, which is the skinniest part of the two continents, just 50 miles wide from ocean to ocean. The infamous Darien Gap.

Are you wondering what this all has to do with you, a regular pet owner? Well, for one thing, you deserved to hear the real story of this impressive accomplishment, which you are apparently not going to get from the regular news. Secondly, the barrier structure is undergoing a slow-motion collapse, and it looks like we could be facing Screwworm II. The 2025 sequel to this now vintage monster flick needs a hero to save the day (and our economy, and the domestic food supply). Are you available?

Dr M.S. Regan