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INTRODUCTION.
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.
RECOGNITION.
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.
SIMILAR GROUPS.
Cluster fly (Polienia rudis) with golden hairs on thorax, body dull,
tan to brownish black.
Secondary screwworm fly (Cochliomyia macellaria) with body bluish
green, head orange, legs reddish, and thorax with 3 black stripes.
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.
Dump flies (Hydrotaea spp.) with body bluish black to bronzy black
and shiny, wing with 4th long vein straight.
House (Musca domestics) and flesh (Sarcophaga spp.) flies with body
dull, gray and black, thorax with 4 or 3 dorsal black stripes respectively.
REPRESENTATIVE SPECIES.
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.
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.
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.
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).
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.
BIOLOGY.
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:
- 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.
- 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.
- 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 1 0 days.
- 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.
- 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.
HABITS.
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.
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