''Cochliomyia hominivorax'', the New World screw-worm fly, or screw-worm for short, is a species of

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

fly Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwing ...

that is well known for the way in which its larvae (maggots) eat the living tissue of

warm-blooded Warm-blooded is an informal term referring to animal species which can maintain a body temperature higher than their environment. In particular, homeothermic species maintain a stable body temperature by regulating metabolic processes. The onl ...

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

s. It is present in the New World

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

. There are five species of ''

Cochliomyia ''Cochliomyia'' is a genus in the family Calliphoridae, known as blowflies, in the order Diptera. ''Cochliomyia'' is commonly referred to as the New World screwworm flies, as distinct from Old World screwworm flies. Four species are in this genu ...

'' but only one species of screw-worm fly in the genus is parasitic; there is also a single Old World species in a different genus (''

Chrysomya bezziana ''Chrysomya bezziana'', also known as the Old World screwworm fly or screwworm, is an obligate parasite of mammals. Obligate parasitic flies require a host to complete their development. Named to honor the Italian entomologist Mario Bezzi, this ...

''). Infestation of a live vertebrate animal by a maggot is technically called

myiasis Myiasis is the parasitic infestation of the body of a live animal by fly larvae (maggots) which grow inside the host while feeding on its tissue. Although flies are most commonly attracted to open wounds and urine- or feces-soaked fur, some spec ...

. While the maggots of many fly species eat dead flesh, and may occasionally infest an old and putrid wound, screw-worm maggots are unusual because they attack healthy tissue.

Life cycle

Screw-worm females lay 250–500

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

s in the exposed flesh of warm-blooded animals, including humans, such as in

wound A wound is a rapid onset of injury that involves laceration, lacerated or puncture wound, punctured skin (an ''open'' wound), or a bruise, contusion (a ''closed'' wound) from blunt force physical trauma, trauma or compression. In pathology, a '' ...

s and the

navel The navel (clinically known as the umbilicus, commonly known as the belly button or tummy button) is a protruding, flat, or hollowed area on the abdomen at the attachment site of the umbilical cord. All placental mammals have a navel, although ...

s of newborn animals. The larvae hatch and burrow into the surrounding tissue as they feed. Should the wound be disturbed during this time, the larvae burrow or "screw" deeper into the flesh, thus the insect's name. The maggots are capable of causing severe tissue damage or even

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

to the host. About three to seven days after hatching, the larvae fall to the ground to

pupate A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...

. The pupae reach the adult stage about seven days later. Female screw-worm flies mate four to five days after hatching. The entire lifecycle is around 20 days. A female can lay up to 3,000 eggs and fly up to during her life.

Control

The

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

officially eradicated the screw-worm in 1982 using the

sterile insect technique The sterile insect technique (SIT) is a method of biological insect control, whereby overwhelming numbers of sterile insects are released into the wild. The released insects are preferably male, as this is more cost-effective and the females ma ...

. However, a 2016 outbreak occurred in

Monroe County, Florida Monroe County is a county in the state of Florida. As of the 2020 census, the population was 82,874. Its county seat is Key West. Monroe County includes the islands of the Florida Keys and comprises the Key West Micropolitan Statistical Area. ...

. The screw-worm was eradicated in

Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...

and

Belize Belize (; bzj, Bileez) is a Caribbean and Central American country on the northeastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a wate ...

in 1994,

El Salvador El Salvador (; , meaning " The Saviour"), officially the Republic of El Salvador ( es, República de El Salvador), is a country in Central America. It is bordered on the northeast by Honduras, on the northwest by Guatemala, and on the south b ...

in 1995, and

Honduras Honduras, officially the Republic of Honduras, is a country in Central America. The republic of Honduras is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Oce ...

in 1996. Campaigns against the flies continue in

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

Nicaragua Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the cou ...

Costa Rica Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the no ...

Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...

, and

Jamaica Jamaica (; ) is an island country situated in the Caribbean Sea. Spanning in area, it is the third-largest island of the Greater Antilles and the Caribbean (after Cuba and Hispaniola). Jamaica lies about south of Cuba, and west of His ...

with financial assistance from the

United States Department of Agriculture The United States Department of Agriculture (USDA) is the United States federal executive departments, federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, ...

, which tries to push back the parasite beyond the narrow and easily controlled

Isthmus of Panama The Isthmus of Panama ( es, Istmo de Panamá), also historically known as the Isthmus of Darien (), is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country ...

Etymology

From the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''kochlias'' (snail with a spiral shell) + ''myia'' (fly) and the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''hominis'' (man) + ''vorax'' (consuming), ''Cochliomyia hominivorax'', or the New World screw-worm fly (formerly ''Callitroga'' (

''kallos'', (beautiful), + ''trogein'', (to gnaw), americana), was first described by French entomologist Charles Coquerel in 1858.

In popular culture

The 1977 science fiction story " The Screwfly Solution" imagines aliens exterminating humans in a similar fashion. In Carmen Mola's detective novel ''La novia gitana'' (2018), and in ''The Dante Club'' (2003) by Matthew Pearl, ''Cochliomyia hominivorax'' is used as a murder weapon by introducing eggs or larvae into the body of an intended victim. In the television series ''

BrainDead ''BrainDead'' is an American political satire science fiction comedy-drama television series created by Robert and Michelle King. The series stars Mary Elizabeth Winstead as Laurel Healy, a documentary film-maker who takes a job working for he ...

'' (2016), an extraterrestrial version of the screw-worm causes the hosts to become overzealous about their politics and health.

References

External links

Species Profile - Screwworm (''Cochliomyia hominivorax'')
National Invasive Species Information Center,

United States National Agricultural Library The United States National Agricultural Library (NAL) is one of the world's largest agricultural research libraries, and serves as a national library of the United States and as the library of the United States Department of Agriculture. Located ...