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Sterile Flies vs. the Screwworm, High school

A sterile screwworm fly on the window of a plane flying over Texas near the Mexico border

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?

Sterile flies beat a flesh-eating fly

The screwworm is a fly whose babies eat living animals. In 2026, the fly is back in Texas for the first time in decades. Years ago, scientists wiped out the fly in the United States by releasing millions of male flies that could not make babies. Now USDA is releasing sterile flies in Texas again.

A bunch of freshly pulled red radishes lying on garden soil
A radish is a root you can eat. Radish comes from the same Latin word rādīx.

Your word of the day is

ih-RAD-ih-kayt

e-outfrom Latin ē-
radic-rootfrom Latin rādīx
-atemakes the word an actionfrom Latin -ātus

To get rid of something completely.

A sterile screwworm fly on a plane window high above Texas

Female screwworm flies mate only once in their lives.

Why would releasing sterile males work less well against an insect whose females mate many times?

Containers packed with about 2 million sterile screwworm flies, ready to load onto a release plane

On Curaçao in 1954, 28% of egg masses were sterile at 200 sterile flies per square mile, and 53% were sterile at 800.

Why do more sterile flies per square mile mean a larger share of sterile screwworm egg masses?

View from a camera on the outside of a plane as it starts releasing sterile screwworm flies over Texas near the Mexico border

USDA sterilizes screwworms by exposing the pupae to gamma radiation.

Why does the radiation dose have to sterilize screwworms without leaving the males too weak to fly and mate?

Video of cows grazing in a sunny green pasture

Since 2006, sterile flies released at a barrier in Panama kept screwworms from moving north out of South America.

Why does the Panama sterile fly barrier have to keep running every week, even in years with no screwworms north of the barrier?

A twin-propeller plane fitted with chutes for releasing sterile screwworm flies, flying back to its base in Edinburg, Texas

Claim, evidence, reasoning

In a model valley, spraying and 18,000 sterile males each cut 2,000 wild females to 1,000 in generation 2. By generation 5, Plan A has 125 females and Plan B has 0.

Which claim about a small screwworm population does the model back up?

A record sheet that follows one batch of Mexican fruit fly larvae through each stage at a Texas fly-rearing plant

Claim, evidence, reasoning

Which evidence from the model backs the claim that sterile flies work better once a screwworm population is small?

Portrait of USDA entomologist Edward F. Knipling, who came up with the sterile insect technique

Claim, evidence, reasoning

Which reasoning connects the evidence to the claim that sterile flies work better once a screwworm population is small?

A machine that coats sterile screwworm pupae in a dry fluorescent dye at the USDA sterile fly center in Edinburg, Texas

A sterile fly plant in Panama makes about 100 million sterile flies a week.

Which statement about the safety of sterile screwworm flies matches what USDA says?

Cattle in Mexico wait behind the border fence to cross into the United States at Douglas, Arizona

Which risk comes with stopping weekly sterile fly releases in years with no screwworm cases?

A narrow window inside a plane shows sterile screwworm flies entering the release chute, with Texas land passing below

Each female screwworm mates once, and sterile males far outnumber wild males.

How do a female screwworm’s single mating and the ratio of sterile to wild males work together to wipe out a population?

USDA workers give medicine to a deer and mark it on Big Pine Key, Florida, during a screwworm outbreak

Lesson complete

Today’s word

eradicate

ih-RAD-ih-kayt

To remove or destroy completely.

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Sources
  1. Edward F. Knipling, USDA, Golden Goose Award profile, 2016
  2. Roy Melvin and Raymond C. Bushland, USDA, 1936 and 1940, as described in Baumhover, 2002
  3. USDA Animal and Plant Health Inspection Service, with the Texas Animal Health Commission, USDA, June 3, 2026 and June 5, 2026
  4. COPEG, run jointly by USDA and Panama’s Ministry of Agriculture Development, USDA sterile fly production page
  5. R. Henry, Emerging Infectious Diseases, 2019
  6. USDA National Agricultural Library, “STOP Screwworms” exhibit
  7. USDA APHIS, Animal Health Officials Respond to Second Detection of New World Screwworm in the United States, June 5, 2026
  8. USDA APHIS, New World screwworm, Using sterile insect technique, Sterile fly production and dispersal, Screwworm.gov and Current status
  9. Vision and Change core concepts and competencies, as summarized in Brownell and others, CBE Life Sciences Education, 2014
  10. Word origins from Dictionary.com: eradicate, radical, radish, radicle, voracious, carnivore, Homo sapiens
  11. Spanish and French words from Wiktionary: eradicate, radix