Fly is the common name used to refer to a range of insects which only have two wings. That includes fruit flies, blow flies(blue bottles/ green bottles) and mosquitoes. The common housefly and bluebottle are the flies that most frequently cause a nuisance in the home.
However, all flies can cause problems as they can carry bacteria and can transmit diseases via body hairs on their tarsi and through saliva and faeces.
The common name of blowfly refers to the fly's deposition of eggs, and comes from antiquity with references dating back into the 16th century. The common name of bottle probably comes from "bot" which is an old term for maggot, thus bottle would mean a little maggot. Alternatively, the name bottle fly may reflect the shiny, glass-like or metallic coloration of those flies. These flies are more than just a nuisance; they are of medical importance because of their mechanical transmission of disease organisms and ability to cause myiasis (infestation of tissues/cavities) in humans and animals. About 80 species occur throughout the United States and Canada.
Blow flies / Bottle flies Adult blow flies / bottle flies measure 1/8 to 5/8 inch long, making them somewhat larger than house flies. They are partly or wholly metallic blue, green, bronze, brassy or black and have sponging-sucking mouthparts.
The mature larvae (maggots) are 3/8 to 7/8 inches long, eyeless, legless, and tapering narrower towards the pointed head from the large rounded rear segment. The head contains a pair of dark mouth hooks. The larvae are pale yellow to white and breath through spiracles (breathing pores) found at the rear of the body.
Blow flies / Bottle fliesThe cluster fly (Pollenia rudis) has golden hairs on the thorax and a dull grayish-tan or grayishbrown overall coloration. The house fly (Musca domestica) and flesh flies (Sarcophaga species) have a dull, gray and black body and the thorax has 4 or 3 dorsal black stripes, respectively.
The bluebottle flies, Calliphora vicina and Calliphora vomitoria, measure 1/4 to 9/16 inch long and have a dull bluish-black thorax and a shiny metallic dark blue abdomen.
The bronzebottle fly, Phaenicia pallescens (formerly Phaenicia cuprina), are 3/16 to 3/8 inch long with a shiny thorax and abdomen that are colored metallic bronze.
The greenbottle flies, Lucilia illustris and Phaenicia sericata, range about 1/4 to 3/8 inch long and have a shiny metallic green thorax and abdomen without stripes.
Female blowflies lay their eggs (up to 2,373) on suitable larval food material. Upon hatching, the larvae may feed on the surface and then burrow into the food material, which is less decayed. Larvae pass through 3 instars. Mature larvae usually leave their food material to pupate. Most species pupate within the top 2 inches of the soil. They may overwinter as mature larvae, pupae or adults. Biological notes and developmental times for some of the more common species can be summarized as follows:
The bluebottle fly (Calliphora vicina) deposits up to about 180 eggs at one time, with a lifetime total of 540 to 720. At 25-35°F and 40% RH, eggs hatch in about 11 hours. The 3 larval instars require 3 to 9 days, depending on latitude and climate, while the pupa stage lasts 7 to 10 days. To summarize, development time (egg to adult) requires 15 to 20 days.
The bronzebottle fly (Phaenicia pallescens/formerly Phaenicia cuprina) deposits eggs in batches of about 100. Eggs hatch in 8 to 15 hours, depending on temperature. Eggs do not hatch below 74°F or above 104°F. The 3 instars require about 72 hours under favorable temperatures. The pupa stage lasts 6 to 7 days in the summer to weeks in cold weather. Developmental time (egg to adult) may be as short as about 10 days.
The greenbottle fly (Phaenicia sericata) females lay about 180 eggs at one time, with a lifetime total of up to 2,373. Eggs hatch in 8 to 43 hours, depending on temperature. Eggs do not hatch below 59°F or above 99°F. The 1st instar lasts 2 to 3 hours and is non-feeding; the 2nd instar requires 1.5 to 9.5 days and feeds, and the 3rd instar is non-feeding and mobile. The pupa stage lasts 3 to 5 days during the summer. Adult preoviposition (waiting time before egg-laying) probably last 5 to 9 days. Developmental time (egg to adult) may require 10 days or longer.
Blow fly disease carrying possibilities are often overlooked. Because many species feed on filth such as human excrement and sewage and/or develop in the carcasses of infected animals, these flies may easily infect the food humans eat. Disease organisms may be mechanically transferred via external body surfaces, by their infected fluids during frequent regurgitation, and by infected fecal deposits. The list of diseases associated with intestinal track problems is nearly identical to that for the housefly, with some of the better-known including Entamoeba coli and Shigella dysenteriae, which cause diarrhea, and Vibrio comma which causes cholera. Non-intestinal disease organisms include plague (Pasteurella pestis), anthrax (Bacillus authracis), tuberculosis (Mycobacterium tuberculosis), and tularemia (Pasteurella tularensis).
Myiasis refers to any disease that results from the infestation of human tissues or cavities by fly larvae. Infestation by Callitroga Americana can result in death (8% mortality in 179 cases reported in 1933). "Surgical maggots" are the larvae of some blow flies, which actually help clean infected wounds and promote healing. Intestinal myiasis is usually accidental and has involved species of Chrysomya, Lucilia, Calliphora, and Phaenicia, which can result in diarrhea with blood discharge and living or dead larvae being expelled with the vomit and/or stool. All 3 representative species highlighted above are recorded as causing myiasis in humans.
Most species develop in meat or animal carcasses, but if these are not available they will use animal excrement, decaying vegetation, and garbage. Dead raccoons, possums, rodents, birds, and other small animals can be the source of flies within structures while dog excrement and garbage are common outdoor sources.
These flies are usually the first insects to arrive and infest after an animal dies. Forensic entomologists often rely on their knowledge of the development times of blow fly larvae to help determine the time of death in murder cases.