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Chrysomya megacephala

Chrysomya megacephala, more commonly known as the oriental latrine fly, is a warm-weather fly with a greenish-blue metallic box-like body which belongs to the family Calliphoridae (blowflies). This fly can be a nuisance to humans and even cause accidental myiasis, infestation of living bodies with maggots.[1] C. megacephala contributes to the evolution of some insects, influences animal atmospheres, is injurious to human public health, and is a tool in forensic entomology.

Geographical distribution[edit]

Regions and areas found[edit]

C. megacephala extends across vast regions of the world. It is particularly prevalent in the Oriental region and the Australasian region,[2] including the east coast of Queensland and New South Wales. It is found in Japan and Palearctic regions as well. Since the 1970s, C. megacephala has extended to different areas of the world, encroaching on the new territories of New Zealand and Africa,[3] along with South, Central, and North America. C. megacephala began penetrating the United States by means of harbors and airports.[4] The oriental latrine fly has been found in California,[5] as well as Texas,[6] Louisiana[7] and Hawaii.[8] C. megacephala exists in two forms, the normal and the derived. Tropical forests on the South Pacific islands, such as Samoa, are home to the normal form; normal is considered the plesiomorphic form of C. megacephala. The derived form is thought to have emerged from Papua New Guinea and is said to be synanthropic, ecologically associated with humans.


C. megacephala prefers to live in climates that are warm most of the year. There seems to be a correlation between warm temperatures and higher fecundity. In high densities of larvae, where many in one small area compete for the same food source, fecundity is less. Where there is more food, there are larger adults and higher fecundity. A correlation between wing size and temperature and tibia size and temperature has been found in this species: as temperature increases, wing and tibia size increase. There was a similar relationship between wing and tibia size and fecundity. All three of these values-- fecundity, wing size and tibia size-- are found to stay within the same range throughout the year, so a seasonal correlation seems to be absent. These laboratory findings are true of this species in a tropical environment, namely Brazil. Researchers find this surprising, since this fly is present in high numbers in warm weather and low numbers in cold weather. It was expected that the flies would be smaller during the warmer months, as in other life tables constructed with other Dipteran species. The majority of Dipteran species that have had a life table constructed have demonstrated a tendency for smaller bodies in the warmer months. It has also been found that C. megacephala has a long lifespan as an adult which, in part, has helped this species become so successful at invading so many geographical areas. The long adult lifespan means that the parents are present to rear the offspring, ensuring their survival.[9]

Life cycle[edit]


Flies laying eggs on a dead baby bird.

This fly species is known to breed in human feces, meat and fish. Developmental stages include egg, larva and pupa. A female fly may lay as many as 200 to 300 eggs.[10] Larval stages include first, second and third instals or growth periods.[11] C. megacephala eggs take approximately one day to develop, while the larva take 5.4 days and the pupa 5.3 days.[12] Population numbers as well as body size are greatly influenced by temperature.[13] After completing all developmental stages, the C. megacephala life cycle lasts approximately 7 days.[14] Since C. megacephala has become forensically important, knowledge of development rates for these blowflies has become a necessity. C. megacephala development appears to be linked with surrounding temperature and length of time spent feeding in the larval stage. Development rate is mainly dependent on temperature: the lower the temperature, the more slowly the larvae develop; higher temperatures mean faster larval development.[15] Most studies on development rates are conducted at 27 °C., at which temperature eggs hatch in 18 hours; the first molt occurs in 30 hours, the second molt in 72 and pupation after 144 hours; the adult emerges at around 234 hours. It is noted that these intervals can vary depending on geographical location; other environmental factors can determine how long flies will stay in the larval stage. Males tend to emerge only two or three hours ahead of the females.[16]

Reproduction and survival rates[edit]

Reproduction and survival rates of C. megacephala are closely related to developmental factors. The amount of available food is important in determining survival and reproduction. Competition from larvae of other species, such as C. rufifacies, is another limiting factor.[17] When competing larvae are present, time spent feeding is shortened, which leads to early pupation and smaller adults. This will then hasten the reproduction of C. megacephala. C. rufifacies is known to cannibalize maggot masses and is thus a huge competitor.[18]


C. megacephala's appearance helps in determining the age of the species as well as distinguishing it from other species. Eggs are "oval with one flat face and another convex".[19] Adult flies reflect a metallic blue-green color on their thorax and abdomen and have yellow gena, or cheeks.[20] Larvae vary in size according to instar and are shaped more thickly towards the rear.[21] C. megacephala are described as having large red eyes, those of males close together and those of females farther apart.[22] Also, the cercus of the male is longer than that of the female.[23]

Forensic science[edit]

Importance in forensic science[edit]

C. megacephala is considered important to forensic science because it is one of the first to show up on a corpse. A post-mortem interval can be easily calculated when Chrysomya megacephala larvae are found on a body. In many areas of the world most forensic entomology cases have either C. rufifacies or Chrysomya megacephala found on the decaying corpse; mitochondrial DNA is mainly used to determine subfamilies of Chrysomyinae.[24] The species' wide geographical distribution and high fecundity make it useful in forensic cases. From studies of insects collected off corpses it has been concluded that 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. Knowing they must look under the body and in adjacent areas can be vital information for a case.[25]

Specific case studies[edit]

One study in Thailand was used to compare and note what species of insects were found on 30 cadavers, which were grouped by the environment they were found in: urban-outdoor, urban-indoor or forested area. C. megacephala was the most common fly, being found on 20 of the 30 bodies. Calliphoridae were, by far, the most common family of flies found on all these cadavers. Chrysomya megacephala was also found in more forested areas than C. rufifacies.[26]

Larval-state poisoning detection[edit]

In any part of the world that uses organophosphates, C. megacephala could prove to be beneficial. Organophosphate compounds are used in agriculture and are highly toxic.[27] Organophosphate poisoning 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, an organophosphate insecticide,[28] 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 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.[29]

Use in research other than forensics[edit]

C. megacephala has a beneficial and practical value apart from being significant in forensic investigations; this blowfly is the source of pollination 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.[30]

Larval competition[edit]

When C. megacephala is found on a body, C. rufifacies is not far behind. C. 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. C. rufifacies is known to cannibalize when food resources get low, but despite this apparent advantage it had a lower survival rate than C. megacephala. 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. This is helpful to know in court cases because it could affect the estimate of 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.[31]

Predators and prey[edit]

Chrysomya albiceps is also known to predate on C. megacephala during the larval stage when they must compete for the same food source.[32] Beetles are also known to predate on C. megacephala. C. megacephala is not predaceous in the adult or larval form, preferring to feed on necrophagous material of any kind, such as fish, cows and humans.

Causing problems[edit]

Agricultural importance[edit]

C. megacephala causes myiasis in humans and animals. This causes losses in cattle and fish industries all over the world. Also, studies are being done on C. megacephala to determine its role as a vector for diarrhea-causing bacteria such as E-coli. Actual transmission has not been completely isolated, but there are three theories on the way disease/bacteria may be transmitted: through the flies’ saliva, feces, or externally.[17]

Public health importance and management control[edit]

Although this group can aid in pollination, C. megacephala can cause many problems as well. C. megacephala are known to be the source of accidental (secondary) myiasis in humans, meaning that these flies do not pierce the skin but invade an open wound.[33] In Thailand the first record of myiasis was that of a male, 53, where C. megacephala and C. rufifacies in their third instar accumulated within a tumor lesion in the male’s right lower leg; however, of the myiasis cases that are recorded, most do not involve C. megacephala and C. rufifacies.[34] C. megacephala likes filth and even lays its eggs on human feces, and after landing on the feces the flies will land on human food.[35] This is how C. megacephala spreads disease, and it is a carrier of pathogens, such as bacteria, protozoan cysts, and helminth eggs, to human food.[27] Not only is this group a huge nuisance, it causes a huge economic problem in Asia, Africa, and the Pacific. In these areas sun-drying fish is a method of preserving fish to send them from where they are caught to the markets and consumers. Ice can be used to preserve the fish as well, but these areas are underdeveloped and often cannot afford this method. However, blowfly larvae tend to infect these sun-dried fish when the weather is warm and humid. An experiment was done to observe which flies show up around these sun-dried fish the most, and 95% were C. megacephala.[36] One technique to control this group is using an odor that the flies are attracted to, so the flies can be trapped.[33] Also, insecticides can be used to handle the problem of Chrysomya megacephala, but sometimes resistance is built up to this control mechanism.[37]

See also[edit]


  1. ^ Brundage, Adrienne. “Entomology”. Forensic Entomology Class Lecture. Texas A&M University, College Station. 2 Mar. 2009.
  2. ^ Wall Richard, and David Shearer. Veterinary Entomology: Arthropod Ectoparasites of Veterinary Importance . London: Springer, 1997.
  3. ^ Williams KA, Villet MH (2006). "A new and earlier record of Chrysomya megacephala in South Africa, with notes on another exotic species, Calliphora vicina (Diptera: Calliphoridae)" (PDF). African Invertebrates 47: 347–350. 
  4. ^ Williams KA, Villet MH (December 2006). "A new and earlier record of Chrysomya megacephala in South Africa" (PDF). African Invertebrates 47: 349. 
  5. ^ Gordoy WAC, et al. (September–October 1996). "Dynamics of Experimental Populations of Native and Introduced Blowflies (Diptera: Calliphoridae): Mathematical Modelling and the Transition from Asymptotic Equilibrium to Bounded Oscillations". Memorias do Instituto Oswaldo Cruz 91 (5): 639–40. PMID 9137751. 
  6. ^ Wells JD (May 1991). "Chrysomya megacephala (Diptera: Calliphoridae) has reached the continental United States: review of its biology, pest status, and spread around the world". J. Med. Entomol. 28 (3): 471–3. PMID 1875378. 
  7. ^ Pharr, Lauren R. 2009. A Taphonomic Model of Concealment: Decomposition and the Postmortem Interval (PMI) in a 55-Gallon Barrel. M.A. thesis, Louisiana State University.
  8. ^ Goff, M. Lee A Fly for the Prosecution: How Insect Evidence Helps Solve Crimes. Massachusetts: Harvard University Press, 2001.
  9. ^ Tomberlin JK, Reeves WK, Sheppard DC (2001). "First record of Chrysomya megacephala (Calliphoridae: Diptera) in Georgia, USA". Florida Entomologist 84 (2): 300–1. doi:10.2307/3496184. JSTOR 3496184. 
  10. ^ Doe, Peter E. “Fish Drying and Smoking” Production and Quality. CRC Press: 177, 179, 186.,M1
  11. ^ M. Lee Goff. “A Fly for the Prosecution” How Insect Evidence Helps Solve Crimes. Pg. 40,+instars,+pupae,+adult&source=bl&ots=JwrByojFnw&sig=NogsHGe-UrdIEPzw3OQmlAgO6kg&hl=en&ei=tGDGSYfHDIrhtgfHmuzICg&sa=X&oi=book_result&resnum=3&ct=result#PPA40,M1
  12. ^ Refaat M. Gabre, Fatma K. Adham, Hsin Chi. (2005). "Life Table of Chrysomya mecagecephala (Fabricius) (Diptera: Calliphoridae". International Journal of Ecology, Acta Oecologica 27 (3): 179–183 see p. 180. doi:10.1016/j.actao.2004.12.002. 
  13. ^ Regada C, Godoy WAC (2006). "Larval density, temperature and biological aspects of Chrysomya megacephala(Diptera: Calliphoridae)". Arq. Bras. Med. Vet. Zootec. 58 (4): 562–6. doi:10.1590/S0102-09352006000400018. 
  14. ^ Doe, Peter E. “Fish Drying and Smoking” Production and Quality. CRC Press: 177, 179, 186.,M1
  15. ^ Piangjai S, Siriwattanarungsee S, Sukontason KL, Sukontason K (2008). "Morphology and developmental rate of blowflies Chrysomya megacephala and Chrysomya rufifacies in Thailand: application in forensic entomology". Parasitol Res. 102 (6): 1207–16. doi:10.1007/s00436-008-0895-6. PMID 18264799. 
  16. ^ Kurahashi H, Wells JD (1994). "Chrysomya megacephala development: rate, variation and the implications for forensic entomology". Jpn. J. Sant. Zool 45 (4): 303–9. 
  17. ^ a b Bunchoo M, Khantawa B, Piangjai S, Rongsiyam Y, Sukontason KL, Sukontason K (2007). "Comparison between Musca dometica and Chrysomya megacephala as carriers of bacteria in northern Thailand". Southeast Asia J. Trop. Med. Public Health. 
  18. ^ Piangjai S, Siriwattanarungsee S, Sukontason KL, Sukontason K (2008). "Morphology and developmental rate of blowflies Chrysomya megacephala and Chrysomya rufifacies in Thailand: application in forensic entomology". Parasitol Res. 102 (6): 1207–16. doi:10.1007/s00436-008-0895-6. PMID 18264799. 
  19. ^ José Augusto de Oliveira David, Thalita Rocha, and Flávio Henrique Caetano. “Ultramorphological characteristics of Chrysomya megacephala (Diptera, Calliphoridae) eggs and its eclosion” (2008):
  20. ^ Jonathan A. Cammack. “A Survey of the Necrophilous Diptera on the Island of Dominica” Pg. 6 Department of Entomology at Texas A&M University, College Station, TX.
  21. ^ Jason H. Bryd, James L. Castner. “Forensic Entomology; The Utility of Arthropods in Legal Investigations” Pg. 33
  22. ^ Byrd, Jason H., and James L. Castner. Forensic Entomology. Florida: CRC Press, 2001.
  23. ^ Chaiwong, Tarinee; Sukontason, Kom; Olson, Jimmy K.; Kurahashi, Hiromu; Chaithong, Udom; Sukontason, Kabkaew L. (April 2008). "Fine structure of the reproductive system of Chrysomya megacephala". Parasitology Research 102 (5): 973–80. doi:10.1007/s00436-007-0863-6. PMID 18180955. 
  24. ^ Shiuh-Feng S, Yeh T (2008). "Larval competition of Chrysomya megacephala and Chrysomya rufifacies: behavior and ecological studies of two blow fly species of forensic significance". J. Med. Entomol. 45 (4): 785–799. doi:10.1603/0022-2585(2008)45[785:LCOCMA]2.0.CO;2. PMID 18714884. 
  25. ^ Byrd, James H. and James L. Castner. Forensic Entomology: The Utility of Arthropods in Legal Investigations. CRC Press, New York. 2001.
  26. ^ Sukontason, Kom, Paitoon Narongchai, Chaturong Kanchai, Karnda Vichairat, Pongruk Sribanditmongkol, Tanin Bhoopat, Hiromu Kurahashi, Manoch Chockjamsai, Somsak Piangjai, Nophawan Bunchu, Somsak Vongvivach, Wirachai Samai, Tarinee Chaiwong, Rungkanta Methanitikorn, Rachadawan Ngern-Klun, Duanghatai Sripakdee, Worachote Boonsriwong, Sirisuda Siriwattanarungsee, Chaowakit Srimuangwong, Boonsak Hanterdsith, Khankam Chaiwan, Chalard Srisuwan, Surasak Upakut, Kittikhun Moopayak, Roy C. Vogtsberger, Jimmy K. Olson, and Kabkaew L. Sukontason (2007). "Forensic entomology cases in Thailand: a review of cases from 2000-2006". Parasitol Res 101 (5): 1417–23. doi:10.1007/s00436-007-0659-8. PMID 17647017. 
  27. ^ a b Wallman JF (1997). "First Record of the Oriental Latrine Fly, Chrysomya Megacephala, from South Australia" (PDF). Transaction of the Royal Society of S. Aust. 121 (4): 163–4. 
  28. ^ “Organophosphate Toxicity.” Department of Natural Resources. 2008.,1607,7-153-10370_12150_12220-27249--,00.html
  29. ^ Gunatilake, and Lee Goff (1989). "Detection of Organophosphate Poisoning in a Putrefying Body by Analyzing Arthropod Larvae". Journal of Forensic Sciences 34 (3): 714–6. PMID 2738573. 
  30. ^ Gabre RM, et al. (2005). "Life table of Chrysomya megacephala" (PDF). Acta Oecologica 27 (3): 179. doi:10.1016/j.actao.2004.12.002. 
  31. ^ Shiao, Shiuh-Feng and Ta-Chuan Yeh (2008). "Larval Competition of Chrysomya megacephala and Chrysomya rufifacies (Diptera: Calliphoridae): Behavior and Ecological Studies of Two Blow Fly Species of Forensic Significance". J. Med. Entomol. 45. 
  32. ^ Gomes, Leonardo, Marcos Rogério Sanches and Claudio José Von Zuben. 2007. Behavior of the Combined Radial Post-feeding Larval Dispersal of the Blowflies Chrysomya megacephala and Chrysomya albiceps (Diptera, Calliphoridae)
  33. ^ a b Bunchu, Nophawan, et al. (2007). "Behavioral responses of Chrysomya megacephala to natural products". Parasitology Research 102 (3): 419–29. doi:10.1007/s00436-007-0780-8. PMID 18026752. 
  34. ^ Sukontason, Kabkaew L., et al. (2005). "First Report of Human Myiasis Caused by Chrysomya megacephala and Chrysomya rufifacies in Thailand, and Its Implication in Forensic Entomology" (PDF). J. Med. Entomol. 42 (4): 702–4. doi:10.1603/0022-2585(2005)042[0702:FROHMC]2.0.CO;2. PMID 16119563. 
  35. ^ Hui, Yiu H. Handbook of Food Science, Technology, and Engineering. Florida: CRC Press, 2006.
  36. ^ Wall R, Howard JJ,Bindu J (April 2001). "The Seasonal Abundance of Blowflies Infesting Drying Fish in South-West India". Journal of Applied Ecology 38 (2): 339–348. doi:10.1046/j.1365-2664.2001.00588.x. JSTOR 2655802. 
  37. ^ Sripakdee, Duanghatai, et al. (2005). "Effect of Microwave Irradiation on the Blowfly Chrysomya Megacephala" (PDF). Chiang Mai University Research Note 36 (4): 893. 


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