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Sterile Flies vs. the Screwworm

Middle school learnscience.org

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Predict

The screwworm is a fly. Its babies, called larvae, eat the living flesh of animals like cows and deer. Scientists want to get rid of every screwworm fly in the United States. Could releasing millions more screwworm flies help get rid of screwworm flies?

Circle one. Yes / No

Why?

Watch

  1. Sterile flies beat a flesh-eating flyyoutube.com/shorts/1-vnaUjSylQ

Word of the day

Eradicate (ih-RAD-ih-kayt). To get rid of something completely, roots and all.

Word partComes fromMeaning
e-Latin ē-out
radic-Latin rādīxroot
-ateLatin -ātusmakes the word an action
  • A radish is a root you can eat. Radish comes from the same Latin word rādīx.
  • In math, the radical sign (√) stands for a root, as in √9 = 3.

Bonus word. Hominivorax (hom-ih-nih-VOR-ax). The screwworm’s scientific name is Cochliomyia hominivorax. Homini- comes from the Latin word for man, and -vorax means consuming, or eating up. Put together, the name means man-eater.

Questions

  1. A female screwworm fly mates only once in her life. Scientists released male flies that can’t make babies. Scientists call these males sterile. How does mating only once help the sterile males wipe out the screwworm?

    Hint. If her one mate is sterile, can her eggs hatch? Does she get to mate again?

  2. Scientists released far more sterile males than there were wild males, millions of them. Why did scientists need so many more sterile males than wild males?

    Hint. Picture 1 sterile male for every 1 wild male. About how many females would still find a wild male?

  3. The United States got rid of screwworms by 1966. Then, in 2026, a calf in Texas had screwworms. Screwworms still live in Mexico, Central America and South America. How could screwworms get back into Texas after decades away?

    Hint. Flies can fly a long way, and people move animals from place to place.

  4. The early screwworm research cost about $250,000. Getting rid of the screwworm saved ranchers over $200 million a year in the 1950s. The Golden Goose Award honors science that sounded odd but paid off. The award’s write-up says some members of Congress made fun of the screwworm research as a waste of money. Was the screwworm research worth the money? Use the cost and the savings to back up your answer.

    Hint. Compare what the research cost with what it saved.

Exit ticket

Spraying and sterile flies can both cut the number of screwworm flies. Scientists release the same number of sterile males every generation, even as the wild flies get fewer. Why do sterile flies work better and better as the wild flies get fewer?

Hint. If the sterile males stay the same and the wild males drop, what happens to a female’s chance of finding a wild male?

Sources