The Blow Or Bottle Fly

Common Name:
Blow or Bottle Flies
Scientific Name:
Calliphora spp., Phaenicia spp.


The common name of blow fly 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. 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.


Adults about 1/8-5/8" (4-16 mm) long, about house fly size or slightly larger. Color partly or wholly metallic blue, green, or dull brassy, sometimes black. Mouthparts sponging. Antenna with arista plumose (feathery) at least on basal 2/3's. Thorax with postscutum (area below scutum) not developed; usually with 2 notoploural bristles; hindmost posthumeral bristle located lateral to presutural bristle; hypopleuron (plate just above middle coxa) with bristles. Wing with 4th (3rd long) vein (M) strongly angled forward, cell R5 narrowed but rarely closed distally (at wing margin).

Mature larvae about 3/8-7/8" (9-22 mm) long; eyeless, legless, and tapering towards head from large rounded rear segment, head represented by I pair of dark hooks. Color pale yellow to white. Posterior spiracies (breathing pores) flat, 2 plates each with spiracular openings consisting of 3 straight, subparallel slits aligned diagonally, which are completely surrounded by an oval black ridge (peritreme) that has a dark donut-shaped structure (button or eodysial/molting scar) attached to its inner margin, spiracular plates surrounded by 1 0 or more tubercles.


  1. Cluster fly (Polienia rudis) with golden hairs on thorax, body dull, tan to brownish black.

  2. Secondary screwworm fly (Cochliomyia macellaria) with body bluish green, head orange, legs reddish, and thorax with 3 black stripes.

  3. Screwworm fly (Cochliomyia hominivorax) with body metallic black and legs shining greenish black, thorax with 3 dorsal (on top) black stripes but middle stripe shorter than lateral stripes.

  4. Dump flies (Hydrotaea spp.) with body bluish black to bronzy black and shiny, wing with 4th long vein straight.

  5. House (Musca domestics) and flesh (Sarcophaga spp.) flies with body dull, gray and black, thorax with 4 or 3 dorsal black stripes respectively.


  1. Black blow fly, Phormia regina (Meigen). Adults about 1/4-7/16" (6-11 mm) long; thorax and abdomen dark and shiny, thorax black with metallic bluish green luster, abdomen metallic yellowish or bluish green to black, anterior spiracle with red/orange hair (setas), squamae/calypteres (posterior basal wing lobes) white or partly white; found throughout the United States.

  2. Bluebottle flies, Calliphora terraenovae Macquart, C. vicina Robineau-Desvoidy, C. vomitoria (Linnaeus), etc. Adults about 1/4-9/16" (6-14 mm) long; thorax dull, abdomen shiny metallic blue, lower squama/calypter (posterior basal wing lobes, posterior lobe) mostly dark; scutellum with 4-5 pairs of marginal bristles; found throughout the United States but more common in northern half of United States and southern Canada.

  3. Bronzabottle fly, Phaenicia pallescens (Shannon); formerly Phaenicia cuprina Shannon. Adults about 3116-3/8" (5-8.5 mm) long; thorax and abdomen shiny, usually metallic bronze, thorax without stripes, anterior spiracle blackish, squamae/calypters white or partly white, abdomen pollinose (with whitish dusting) dorsally; male with abdominal genitalia (terminal) segments very hairy ventrally, female abdominal ventral surface with variegated pollinosity (whitish dusted areas); found in southern United States.

  4. Greenbottle flies, e.g., Lucilia illustris (Meigen), Phaenicia (Lucilia for Europeans) sericata (Meigen). Adults about 1/4-3/8" (6-9.5 mm) long; thorax and abdomen shiny, usually metallic green, thorax without stripes, anterior spiracle blackish, squamae /calypters white or partly white, abdomen sometimes pollinose (with whitish dusting) on sides and often on venter/below; male with abdominal genitalia concealed (P. sericata) or with scattered hairs (L. illustris), female abdominal ventral surface without variegated pollinosity (whitish dusted areas); found mostly in northern United States and southern Canada (P. sericata) or found throughout but commonly in the Midwestern United States (L. illustris).

  5. The shiny bluebottle fly, Cynomya cadaverina (Robineau-Desvoidy). Adults about 3/8-9/16" (9-14 mm) long; black with gray markings, head with gray or yellow to brownish pile (short, fine hairs/setae), abdomen shiny blue-green, anterior spiracle dark brown, lower squama/calypter (posterior basal wing lobes, posterior lobe) white; scutellum with 3 pairs of marginal bristles; found throughout the United States.


Female flies 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" (51 mm) of the soil. They usually overwinter as mature larvae or pupae.

Biological notes and developmental times for some of the more common species can be summarized as follows:

  1. Black blow fly (P. regina). Eggs are deposited in glued masses of varying numbers. At an optimal 99'F (37'C), eggs hatch in 8.1 hours (range 52 hrs at 59'F/15'C to no hatch at 109'F/43'C). The 3 larval instars require 4-15 days. The pupal stage lasts 3-13 days. In the Dallas, Texas, area developmental time (egg to adult) requires 10-25 days.

  2. Bluebottle fly (C. vicina). Up to about 180 eggs are deposited at one time, with a lifetime total of 540-720. At 25-35'F (-4-1.7'C) and 40% RH, eggs hatch in about 1 1 hours. The 3 larval instars require 3-4 days in eastern Texas, to 6.5-8.75 days (82-F/28-C, 70% RH) in southern Canada, with pupation usually occurring 7.5 days after the egg is laid. The pupal stage lasts 7-10 days in Texas. In eastern Texas, developmental time (egg to adult) requires 15-20 days.

  3. Bronzabottle fly (P. pallescens). Eggs are deposited in batches of about 100. At an optimal 99'F/37'C, eggs hatch in about 7.7 hours (range 15 hrs at 74'F/23'C to 8.9 hrs at 104'F/40'C); no hatch below 74'F/23'C or above 104'F/40'C. The 3 instars require about 72 hours under favorable temperatures. The pupal stage lasts 6-7 days in the summer to weeks in cold weather. Developmental time (egg to adult) may be as short as about 10 days.

  4. Greenbottle fly (P. sericata). Females lay about 180 eggs at one time, with a lifetime total of up to 2,373. At an optimal 94'F/34'C, eggs hatch in 8.1 hours (range 42.4 hrs at 59'F/1 5'C to 8.1 hrs at 99'F/37'C; no hatch above 99'F/37'C). The 1 st instar lasts 2-3 hours and is non-feeding, 2nd instar requires 1.5-9.5 days and feeds, and 3rd instar is non-feeding and mobile. The pupal stage lasts 3-5 days during the summer. Adult preoviposition probably lasts 5-9 days. Developmental time (egg to adult) may require 10 days or longer.

  5. Shiny bluebottle fly (C. cadaverina). Females lay up to 25-50 eggs at one time. Eggs hatch within 24-72 hours. The 3 instars require 3-5 days, with the puparium being formed 2-36 days later. The pupal stage lasts 6-58 days. The developmental time (egg to adult) requires 19-99 days. Adult preoviposition lasts 7-20 days.

Note that in the laboratory at 72 degrees F/22degrees C and 50% RH, the developmental times in days for these 5 species is 11 (range 10-1 2), 18 (range 14-25), no data, 12 (range 12- 15), and 18 (range 17-19) respectively.

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 organisrhs may be mechanically transferred via external body surfaces, by their infected fluids during frequent regurgitation, and/or by infected fecal deposits. The list of diseases associated with intestinal track problems is nearly identical to that for the house fly, with some of the better known including Entamoeba coli (Migula) and Shigelia dysenteriae (Shiga) which cause diarrhea, and Vibrio comma (Schroeter) which causes cholera. Non- intestinal disease organisms include plague (Pasteurella pestis (Lehmann & Neumann)), anthrax (Bacillus authracis Cohn), tuberculosis (Mycobacterium tuberculosis (Zopf)), and tularemia (Pasteurella tularensis (McCoy & Chapin)).

Myiasis refers to any disease that results from the infestation of tissues or cavities by fly larvae. Infestation by Caffitroga americans Cushing & Patton can result in death (8% mortality in 179 cases reported in 1933). "Surgical maggots" are the larvae of some species which actually help clean infected wounds and promote healing. Intestinal myiasis is usually accidental and has involved species of Chrysomya, Lucitia, Calliphora, and Phaenicia, which can result in diarrhea with blood discharge and living and/or dead larvae being expelled with the vomit and/or stool. All 8 representative species listed 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/or garbage. Dead 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. Their larvae are often used by forensic entomologists to help determine the time of death in murder cases.

Some species are strong fliers. For example, marked and released black blowflies (P. regina) had 13% trapped between 4-28 miles (6.4-46 km) from the point of origin and 8+% at or beyond 1 1 miles (1 8 km). They are most active on warm, sunny days, and primarily rest on cool and/or cloudy days. Inside, they are attracted to the bright light coming through windows.