C. macellaria larvae do not have pigmented tracheal trunks; they have spines in a V shape on the anal protuberance and no oral sclerite.

C. hominivorax larvae dive head-first into whatever food source is nearest, and burrow deeper, eating into live flesh if available.

Males mature rapidly, and spend their time waiting and eating nearby vegetation and the nectar of flowers.

[5][6] The primary screwworm, C. hominivorax, is a parasitic species, whose larvae are renowned for eating and infesting the flesh of living organisms, primarily warm-blooded animals such as cattle and other livestock.

Flystrike may occur due to such farming processes as branding, castrating, dehorning, and tailing of the host animals.

The larvae are responsible for their common name, the screwworm, because they possess small spines on each body segment that resemble a screw's threads.

After the larvae hatch, they dive into the wound and burrow deeper, perpendicular to the skin surface, eating into live flesh, again resembling a screw being driven into an object.

[5] The sterile insect technique was proposed by scientists Edward F. Knipling and Raymond C. Bushland, and was rapidly adopted by the United States Department of Agriculture in 1958.

Because the agricultural industry was losing millions of dollars annually due to treatment and loss of fly-struck animals, this solution was quickly approved for testing.

The program was then applied throughout the southern United States, and eventually adopted through much of Mexico in 1972 and parts of Central and South America.

Livestock there continue to be vulnerable, however, and strict laws regarding animal inspection and reporting of suspected infestations remain in place.

Eventually, the infested region spanned from the Mediterranean coast to the Sahara Desert, threatening the more than 2.7 million animals susceptible to C. hominivorax that inhabited the area.

Traditional control methods using veterinary assessment and treatment of individual animals were insufficient to contain the widely dispersed outbreak, so the United Nations Food and Agriculture Organization launched a program based on the sterile insect technique.

[12] About 1.26 billion sterile flies were produced in Mexico, shipped to the infested area, and released to mate with their wild counterparts.

[5][13] The North African outbreak both provided proof of the sterile male technique's efficacy and led to numerous enhancements in its implementation; after 1991, it entered into use across parts of Central and South America.

However, the inaccessibility of some areas that the fly inhabits, language differences, and the need of constant vigilance have slowed the eradication of this species.

[14] The secondary screwworm, C. macellaria, is a flesh-eating fly whose larvae consume only necrotic tissue, either that of carrion or of an animal or human host (myiasis).

This important distinction between C. macellaria and C. hominivorax was not understood for much of medical history; myiasis of humans and animals was viewed as universally disastrous.

Fortunately, with the recent advent of molecular evidence, C. macellaria maggots removed from a body and boiled to sterility can now provide vital information regarding a victim and determining a post mortem interval.

Forensic entomologists can use various extraction methods to test the composition of the alimentary canal of the larvae to determine if victims had any drugs or mind-altering substances in their systems before they were killed.

The most effective way to differentiate the two is to note the absence on C. macellaria of the distinctive pigmented tracheal tubes, as well as the presence of a V-shaped pattern of spines on the anal protuberance, and the lack of an oral sclerite.

[2] Interaction between humans and C. macellaria outside of accidental secondary myiasis has been largely unremarkable, with the notable exception of their early use in surgical maggot therapy.

As the infestation increases, the victim begins to experience escalating tissue irritation, and in the case of domesticated animals, may be observed to become withdrawn, listless, and anorexic.

The obvious first step is the manual removal of the maggots, generally using tweezers or forceps to seize the larva at the posterior end as the spiracles emerge to allow respiration.

Flies can also be induced to lay their eggs in hair or wool that is matted thickly and stained with any bodily fluid.

The larvae can be diagnosed and identified by a trained professional based on larval size, shape (again following the spiraled screw-shape), and ultimately on spiracle pattern.