''Chrysomya megacephala'', more commonly known as the oriental latrine fly or oriental blue fly, is a member of the family
Calliphoridae
The Calliphoridae (commonly known as blow flies, blow-flies, carrion flies, bluebottles, greenbottles, or cluster flies) are a family of insects in the order Diptera, with almost 1,900 known species. The maggot larvae, often used as fishing ba ...
(blowflies). It is a warm-weather
fly
Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwing ...
with a greenish-blue metallic box-like body. The fly infests corpses soon after death, making it important to forensic science. This fly is implicated in some public health issues; it can cause accidental
myiasis
Myiasis is the parasitic infestation of the body of a live animal by fly larvae (maggots) which grow inside the host while feeding on its tissue. Although flies are most commonly attracted to open wounds and urine- or feces-soaked fur, some spec ...
, and also infects fish and livestock.
Description
''Chrysomya megacephalas eggs are "oval with one flat face and another convex". Adult flies reflect a metallic blue-green color on their
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...
and
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
and have yellow gena, or cheeks. Larvae vary in size according to instar and are shaped more thickly towards the rear. ''C. megacephala'' have large red eyes, those of males being close together, and those of females farther apart. The ''cercus'' of the male is longer than that of the female.
Distribution and habitat
''Chrysomya megacephala'' has a wide geographical distribution. It is most common in the
Oriental
The Orient is a term for the East in relation to Europe, traditionally comprising anything belonging to the Eastern world. It is the antonym of ''Occident'', the Western World. In English, it is largely a metonym for, and coterminous with, the ...
and
Australasian realm
The Australasian realm is a biogeographic realm that is coincident with, but not (by some definitions) the same as, the geographical region of Australasia. The realm includes Australia, the island of New Guinea (comprising Papua New Guinea and ...
s. It is also found in
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
and the
Palearctic realm
The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa.
The realm consists of several bioregions: the Euro-Sibe ...
. The range of ''C. megacephala'' has grown since the 1970s, with the species expanding into
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
and
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
, along with
South
South is one of the cardinal directions or Points of the compass, compass points. The direction is the opposite of north and is perpendicular to both east and west.
Etymology
The word ''south'' comes from Old English ''sūþ'', from earlier Pro ...
,
Central
Central is an adjective usually referring to being in the center of some place or (mathematical) object.
Central may also refer to:
Directions and generalised locations
* Central Africa, a region in the centre of Africa continent, also known as ...
, and
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. ''C. megacephala'' entered the United States through harbors and airports. The fly has been found in California, as well as Texas, Louisiana, and Hawaii. ''C. megacephala'' exists in two forms, the normal and the derived.
Tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
forests on the
Pacific Islands
Collectively called the Pacific Islands, the islands in the Pacific Ocean are further categorized into three major island groups: Melanesia, Micronesia, and Polynesia. Depending on the context, the term ''Pacific Islands'' may refer to one of se ...
, such as
Samoa
Samoa, officially the Independent State of Samoa; sm, Sāmoa, and until 1997 known as Western Samoa, is a Polynesian island country consisting of two main islands (Savai'i and Upolu); two smaller, inhabited islands (Manono Island, Manono an ...
, are home to the normal form; the normal is considered to be the plesiomorphic form of ''C. megacephala''. The derived form is thought to have emerged from
Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
and is said to be
synanthropic
A synanthrope (from the Greek σύν ''syn'', "together with" + ἄνθρωπος ''anthropos'', "man") is a member of a species of wild animal or plant that lives near, and benefits from, an association with human beings and the somewhat artific ...
, or ecologically associated with humans.
Behavior and ecology
Climatic variation
''Chrysomya megacephala'' prefer warm climates, and display a correlation between warmer temperatures and higher
fecundity
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
. In
tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
populations, such as in
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, fertility is also lower in areas with high densities of larvae, where many in one small area compete for the same food source. A correlation between wing size and temperature as well as tibia size and temperature has also been found in this species. There was a similar relationship between wing and tibia size and fecundity. All three of these values variables, fecundity, wing size and tibia size, stay within the same range throughout the year, showing seasonal variation to be absent. This has been of interest to researchers, since this fly is present in high numbers in warm weather and low numbers in cold weather. The majority of
Dipteran
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced m ...
species that have had a life table constructed have demonstrated a tendency for smaller bodies in the warmer months. ''C. megacephala'' has a relatively long lifespan as an adult which has helped the species become successful at invading new geographical areas. The long adult lifespan means that the parents are present to rear the offspring, ensuring their survival.
Reproduction
![Chrysomya megacephala on baby bird](https://upload.wikimedia.org/wikipedia/commons/c/c7/Chrysomya_megacephala_on_baby_bird.jpg)
The developmental stages of ''C. megacephala'' include
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
,
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
and
pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
. A female fly may lay as many as 200 to 300 eggs, often in human feces, meat or fish. Larval stages include first, second and third instals or growth periods. The eggs take approximately one day to develop, while the larvae take 5.4 days and the pupae 5.3 days. Population numbers as well as body size are greatly influenced by temperature. The adult lifespan of the fly is approximately seven days. The development of ''C. megacephala'' is linked to the length of time spent feeding in the larval stage, as well as to temperature; the lower the temperature, the more slowly the larvae develop. In laboratory studies conducted at 27 °C., eggs hatch in 18 hours; the first molt occurs in 30 hours; the second molt in 72 hours; pupation after 144 hours; and the adult emerges after approximately 234 hours. These intervals vary depending on geographical location; other environmental factors also can determine how long flies will stay in the larval stage. Males tend to emerge two or three hours ahead of the females.
The reproduction and survival rates of ''C. megacephala'' are closely related to developmental factors, including the amount of available food, and competition from larvae of other species, such as ''C. rufifacies''.
In the presence of competing larvae, those of ''C. megacephala'' spend less time feeding, leading to early pupation, smaller adults, and early reproduction. The second and third instar larvae of ''C. rufifacies'' are known predator that feeds on the larvae of ''C. megacephala'' when feeding substrate is less or larval density is high. In such cases ''C. megacephala'' tend to disperse early, thus remains malnaurished.
Predators and prey
''Chrysomya albiceps'' is also known to prey on ''C. megacephala'' during the larval stage when they must compete for the same food source. Beetles are also known to prey on ''C. megacephala''. ''C. megacephala'' is not predaceous in the adult or larval form, preferring to feed on
necrophagous
Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...
material of any kind, such as fish, cows and humans.
Larval competition
''Chrysomya megacephala'' larvae are known to compete with ''C. rufifacies'' larvae for food in a mixed-species environment. Research has shown that under specific population densities, ''C. rufifacies'' will facultatively feed on other species of maggots and on its own species. When ''C. rufifacies'' and ''C. megacephala'' larvae are put into cultures separately from one another in high densities, ''C. megacephala'' has a higher rate of survival than ''C. rufifacies''. Both species had a lighter adult weight than normal and pupated earlier. The third instar of ''C. rufifacies'' will eat ''Chrysomya megacephala'' when the larvae are in high density. Despite this predation on ''Chrysomya megacephala'', both species had a lower survival rate, lighter adult weight and pupated early.
Forensic science
Importance in forensic science
''C. megacephala'' is considered important to forensic science because it is one of the first flies to show up on a corpse, and so the time of death can easily be determined when ''Chrysomya megacephala'' larvae are found on a body. In many forensic entomology cases either ''C. rufifacies'' or ''Chrysomya megacephala'' are found on the decaying corpse;
mitochondrial DNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...
is the main method used to determine which subfamily is present. The species' wide geographical distribution and high
fecundity
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...
also make it useful in forensic cases; ''C. megacephala'' is among the most common blowflies found.
Larval dispersion patterns of ''C. megacephala'' also make it forensically important. Knowing that, to pupate, larvae move away from the food source to find a safe place to metamorphose, forensic entomologists can accurately calculate a
post mortem interval
The post-mortem interval (PMI) is the time that has elapsed since an individual's death. When the time of death is not known, the interval may be estimated, and so an approximate time of death established. Postmortem interval estimations can ra ...
. Knowledge of larval competition is also useful in forensic studies, because it could affect the estimate of the time of death. If only ''C. rufifacies'' is found on a body, it is not accurate to use only this species to calculate a time of colonization. The colonization of ''C. megacephala'' prior to ''C. rufifacies'' must be taken into account.
[
]
Larval-state poisoning detection
In any part of the world that uses organophosphates
In organic chemistry, organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure , a central phosphate molecule with alkyl or aromatic substituents. They can be considered ...
, ''C. megacephala'' could prove to be beneficial. Organophosphate compounds are used in agriculture and are highly toxic
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...
. Organophosphate poisoning
Organophosphate poisoning is poisoning due to organophosphates (OPs). Organophosphates are used as insecticides, medications, and nerve agents. Symptoms include increased saliva and tear production, diarrhea, vomiting, small pupils, sweating, mus ...
often causes death, and in many cases, by evaluating the body tissue and fluids, the toxin can be identified as the source of the poisoning. However, it is somewhat difficult to evaluate the body tissue in a body that is exceedingly decomposed. Nevertheless, a medical examiner in Hawaii worked on a case in which poisoning by malathion
Malathion is an organophosphate insecticide which acts as an acetylcholinesterase inhibitor. In the USSR, it was known as carbophos, in New Zealand and Australia as maldison and in South Africa as mercaptothion.
Pesticide use
Malathion is a pesti ...
, an organophosphate insecticide, was thought to be the cause of death. The victim’s stomach contents and body fat were examined and found to have contained malathion. The fly larvae of ''Chrysomya megacephala'' and ''Chrysomya rufifacies
''Chrysomya rufifacies'' is a species belonging to the blow fly family, Calliphoridae, and is most significant in the field of forensic entomology due to its use in establishing or altering ''post mortem ''intervals. The common name for the spe ...
'' were also present at the scene on the body and were tested for malathion. Both of these species did contain malathion, but there had been no previous record of organophosphates in their larvae. Studying larvae from decomposed remains may provide an effective method of determining the presence of these toxins in a body that is extremely decayed.
Use in other research
''Chrysomya megacephala'' has a beneficial and practical value apart from being significant in forensic investigations; this blowfly is the source of pollination
Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...
for mangos in the Australian region. While most areas wish to rid themselves of ''C. megacephala'', Taiwanese farmers have found ways to enhance the population of this blowfly so that more mangos will be pollinated.
Public health and agricultural issues
Myiasis in livestock
''Chrysomya megacephala'' causes myiasis in humans and animals. This causes losses in cattle and fish industries all over the world. Studies are being done on ''C. megacephala'' to determine its role as a vector
Vector most often refers to:
*Euclidean vector, a quantity with a magnitude and a direction
*Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism
Vector may also refer to:
Mathematic ...
for diarrhea-causing bacteria such as ''E. coli''.[
]
Public health importance and management control
''Chrysomya megacephala'' are known to be the source of accidental (secondary) myiasis in humans, where the flies do not pierce the skin but invade an open wound. The first record of human myiasis caused by ''C. megacephala'' and ''C. rufifacies'' was in Thailand, where a 53-year-old man had a tumor lesion where the larvae accumulated. Most recorded myiasis cases, however, do not involve the fly. ''C. megacephala'' is a carrier of pathogens, such as bacteria, protozoan cysts, and helminth
Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schi ...
eggs, to human food, because it lays its eggs on human feces, and will land on human food soon after.
The flies also cause a huge economic problem in Asia, Africa, and the Pacific. In these areas sun-drying is the major method of preserving fish, as ice is typically unaffordable. However, blowfly larvae tend to infect these sun-dried fish when the weather is warm and humid. In an experiment, 95% of the infecting flies were found to be ''C. megacephala''. The flies can be controlled by using an odor that the flies are attracted to trap them.[ Insecticides are also used, although this results in the development of resistance.]
See also
*''Chrysomya bezziana
''Chrysomya bezziana'', also known as the Old World screwworm fly or screwworm, is an obligate parasite of mammals. Obligate parasitic flies require a host to complete their development. Named to honor the Italian entomologist Mario Bezzi, this ...
''
*''Chrysomya albiceps
''Chrysomya albiceps'' is a species belonging to the blow fly family, Calliphoridae.
Taxonomy
''Chrysomya albiceps'' is considered conspecific with '' Chrysomya rufifacies'' by some authorities. The two species have a similar biology and the mo ...
''
*''Chrysomya rufifacies
''Chrysomya rufifacies'' is a species belonging to the blow fly family, Calliphoridae, and is most significant in the field of forensic entomology due to its use in establishing or altering ''post mortem ''intervals. The common name for the spe ...
''
References
{{Taxonbar, from=Q2967396
Calliphoridae
Insects described in 1794
Diptera of Australasia
Taxa named by Johan Christian Fabricius