About Blow Flies
Pollenia rudis, the common blow-fly, has achieved a star status in crime novels and television procedurals that would surprise even that maven of minutae, Sherlock Holmes. Although its cousin, the common house fly, is more common, the blow fly's singular diet makes it a useful ally in forensic and medical science. The distinctive markings of each species allow easy identification for entomologists. This little insect, with its unpleasant habits and reputation, is the subject of studies that have popularized forensic science and provided medical science with a reliable tool for healing.
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Identification
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Blow flies are members of the Calliphoridae family of the Diptora (flies) order of insects. There are several different types of blow flies but most have a shiny, metallic body. Coloring may be green, blue or black. Specific species are identified by the arrangement of hairs, or bristles, on their legs.
The Facts
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The origin of the name "blow fly" is English. Their natural habitat is tropical, including Africa, India, Central America and the southern part of the United States. Growth, lifespan and reproductive habits depend on species and environmental factors. Blow flies lay their eggs in loose soil containing rotting material or in carrion to provide larvae with a ready food supply. It is this last habit that makes them useful to science.
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Significance
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Blow flies have been used by medical practitioners to remove dead tissue and clean wounds since Roman times. Anthropologists have found aboriginal peoples who still use them. Since the larvae, called maggots, eat only dead tissue, they serve to clean wounds and speed healing. Modern doctors use a therapy, called Maggot Debridement Therapy for non-healing wounds. The type of fly used for this is limited to flies bred in laboratory conditions that are unlikely to bring additional infection to the host.
Evolution
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Each variety of blow fly reproduces in a predictable fashion and each stage of development is consistent and governed by temperature. Forensic entomologists have therefore been able to combine this knowledge with weather condition records to determine how long bodies have been deceased and whether there were underlying conditions before death. This application has led entomologists to investigate the activity of a number of insects which can help pinpoint time of death. When data from the insects is combined, the time of death can be identified almost down to the minute.
Benefits
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Research into diseases like gangrene and certain types of ulcers is also benefiting from the study of blow fly habits. Aside from the medical benefits, the study of the blow fly life cycle has opened a new field of forensic science that has implications for medical research. Crime investigation is merely one aspect of the benefits brought from the study of the unsavory little blow fly.
Risk Factors
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Myiasis (a disease caused when fly larvae develop inside, rather than on the surface of, a living host) and certain pathogens, such as those
causing dysentery, can be transmitted by adult flies of any species. Since blow flies are so selective about where they eat and breed, the risks posed by this fly family is not as great as that of its cousin, the house fly.
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Resources
- Photo Credit Wikimedia Commons
