Phormia regina | |
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Genus: | Phormia Robineau-Desvoidy, 1830 |
Species: | P. regina |
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Phormia regina Meigen, 1826 | |
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Phormia regina, the black blow fly, belongs to the blow fly family Calliphoridae and was first described by Johann Wilhelm Meigen. [1]
The black blow fly's wings are specialized with a sharp bend. These flies also have well-developed calypters. Blow flies generally are about the size of a house fly or a little larger, and many are metallic blue or green in color. Key characteristics of this species include black gena, mostly white calypters, and anterior thoracic spiracles that appear to be orange yellow due to being surrounded by bright orange setae. [2] [3]
P. regina is especially important to forensic entomology. Female P. regina, like other blow flies in the family Calliphoridae, oviposit their eggs on carrion, where they hatch. The larvae develop through three instar stages until pupation. [4] Adult black blow flies aggregate on feces in order to mate. The success of these mating interactions has been studied and appears to be related to size and diet of the adult flies. Following successful mating encounters, the adult females are then attracted to decaying material rather quickly for oviposition, [5] allowing forensic entomologists to use development stages of larvae as a clue in determining an approximate time of death. P. regina are extremely common in the United States and other areas in North America. [4] Combined with their importance in forensic entomology, these flies have been relatively well studied, particularly for variables affecting their development.
Phormia regina was described by the German entomologist Johann Wilhelm Meigen in 1826. Its specific epithet is derived from the Latin word regina meaning 'queen'. [1]
Phormia regina adults are metallic blue or green in color and have a distinctive set of orange setae near the anterior thoracic spiracle. [2] They are also recognizable by their black gena (the side of the head below eye level), mostly white calypteres, and the distinctive bend in their wings. [2] [3]
P. regina is commonly found across the entirety of the United States as well as across other regions in North America [4]
P. regina can be found on human corpses, animal carcasses, and feces. Researchers have observed these flies on a wide variety of animal excrement, but at least in the northwestern United States, they exhibit a preference for human, mink, and swine feces. [6] P. regina is predominantly found in the northern United States during spring and summer months, but in the winter they are localized to more southern regions. [7] This localization is tentatively linked to the importance of temperature on their development. [7] These flies prefer rural areas, especially near water sources, as opposed to urban spaces—at least in the San Francisco Bay Area. [8]
The life cycle and development of Phormia regina is similar to that of most other Dipteran species, in which females oviposit their eggs onto a nutrient substrate. Then, after hatching, the larvae feed throughout three instar stages until they have stored up enough calories to commence pupation and finally emerge as adult blow flies. Each transition from first, second, and third instar is marked by a molt, and eventually the third-instar larvae develop sclerotized (hardened) casings which envelop and protect them throughout metamorphosis. [4]
Relatively few studies have been conducted on the adults of this species in comparison to those on larval development, mostly due to the importance of blow fly larvae in determining the post mortem interval (PMI) of corpses during investigations by forensic entomologists. For this reason, many researchers have conducted experiments to investigate the effect of various environmental factors on the duration time of larval development in this species (as well as many others).
Because the larval life cycle of this species is dependent on a climate with temperatures ranging from 12.7°C (55°F) to 35 °C (95 °F), it tends to inhabit the northern regions of the United States during summer months and southern regions in the winter. Researchers have discovered that at 40 to 45 °C, larval development occurs normally until the prepupal stage, at which point a majority of the larvae die. The few able to pupate at these high temperatures do not emerge as adults. The lowest temperature threshold for this species was found to be 12.5 °C below which females will not oviposit. The highest rate of development (with survival into adulthood) was seen at a constant temperature of 35 °C, where the average time of adult emergence was 265 hours (about 11 days). Flies at constant temperatures between 15 and 30 °C (at 5-degree increments) developed slower, with flies at the coolest temperatures taking the longest. Cyclic temperatures ranges of 25 to 35 °C and 15 to 25 °C proved to decrease the rate of development when compared to constant temperatures. (The cyclic temperature data were collected by placing specimens in an incubator which steadily alternated between the maximum and minimum temperatures of a particular 10-degree range (e.g. 25 to 35 °C). Each 10-degree fluctuation took place over a 12-hour span.) [4]
Also, studies have been conducted to assess the effects of light exposure on developmental variability in larvae. Larvae exposed to cyclic photoperiods (shifting intermittently between 12 hours of light to 12 hours of darkness) have higher rates of development than larvae exposed to constant photoperiods (24 hours of light per day). These findings suggest that darkness may be a stimulus for larval growth. However, these variations in light photoperiods failed to influence pupal duration times. [9]
While this species is in the wild, dung constitutes a majority of the nutritional intake used for sexual development in both male and female adults, but diets with higher protein intake better facilitate mating ability of both sexes. Female sexual maturity requires the completion of 10 stages of follicle development in the ovaries to produce eggs that are completely mature, and ovaries in females which have been deprived of a high-protein diet do not develop fully. Although it is possible for females on a diet of only dung to reach the final stage of sexual maturity, it takes much more time than if they were to feed exclusively on beef liver; even then, a lower percentage of those feeding on dung will have fully developed. An experiment by Stoffolano demonstrated this, revealing that 100% of females feeding exclusively on beef liver were able to reach the final stage of sexual development after 13 days, while only 78% of females were able to do so when feeding exclusively on pig dung over a 20-day period. Although some Dipteran species oviposit on dung, P. regina females exclusively deposit their eggs on carrion. [10]
The neuroendocrine system in adult males, which controls their mating behavior, must be stimulated before they will mate with a female. Protein in the male diet is not necessarily needed for this stimulation, but Stoffolano also saw that higher percentages of females were successfully inseminated by male specimens which had been fed either dung or beef liver versus specimens with a diet of only sugar. Protein is not generally necessary for spermatogenesis in male flies, but it is paramount for accessory reproductive gland development, higher rates of copulation, and the capability of impregnating females. [10] An additional study found a positive correlation between male head size and the size of the aedeagi (the external reproductive organs), which has been proposed as a possible reason for lower percentages of insemination between small males and large females within this species. [11]
Feeding habits vary greatly throughout the life cycle of P. regina. The feeding habits of adult flies depend both on sex and reproduction status of the fly. This is particularly important with respect to their protein intake, which literature suggests has an important role in sexual maturation and copulation ability in adult P. regina. [10] [12] Like most other flies, the black blow fly feeds via sponging. Though adults require various types of nutrients, in the wild they are typically able to procure all their nutrition from feces. [13]
Adult females oviposit eggs on carrion. These eggs hatch into larvae that feed on the decaying tissue. [4]
Virgin adult females, when given access to protein and carbohydrate sources, utilize both for food. However, after their emergence as adults, they will gradually increase their protein intake until they are approximately 8 to 10 days old. From here they will continue to intake protein at a relatively constant rate that is lower than their required carbohydrate intake. Once a female has mated, either for the first time or all subsequent times, a spike in protein intake occurs following oviposition of her eggs. [12]
Protein intake in adult male black blow flies follows similar trends to that of virgin adult females; however, they require less total protein than females. The males will gradually increase their protein intake for the first 8–10 days of adulthood. They will then drop their protein intake to a relatively low and constant amount. [12]
Adult black blow flies aggregate on feces, particularly animal dung pats, not only because they act as a food source, but also in order to mate. Some research has suggested a preference for settling on human, swine, and mink feces, but this may be localized to the northwestern region of the United States. [6] P. regina is a panmictic species. [14] Research supports mating success of adult males positively correlates to their size. Larger males have larger aedeagus which leads to more successful insemination of females. The mechanism of how and why larger aedeagus lead to better insemination is unknown. [11]
Female black blow flies each have a pair of ovaries and lateral oviducts, one common oviduct, a vagina, and a bursa copulatrix, which is simply a sac-like cavity within the female that is roughly equivalent to a uterus. Each ovary has a lateral oviduct; these two lateral oviducts meet to form the common oviduct and connect the ovaries to the burs copulatrix. Three spermathecae are connected to the bursa copulatrix via spermathecal ducts, and two accessory glands attach to the bursa copulatrix near the spermathecae entries. The vagina is connected to the bursa copulatrix on the opposite end of the ovaries and allows the male aedeagus access to the bursa copulatrix and spermathecae. [15]
Male black blow flies have an external phallus that is a tube-like structure with unique flaps centrally located. The phallus can be divided up into several different sections. There is the hypophallus, which protrudes from the abdomen of the fly. The cornua, which is the name given to the centrally located wing-like flaps on the phallus, protrude from the hypophallus. A pair of paraphallic bulbs are embedded in the cornua with only their tips jutting out. These bulbs are sclerotized, meaning they are hardened, as are a variety of spines on the outside of the cornua. From the cornua a narrower tube structure, the acrophallus, extends with a terminal fluted opening, referred to as the gonophore, from which sperm and accessory secretions flood. [15]
During mating the tip of the male's phallic structure is near the spermathecal ducts of the female's reproductive system. The wing-like flap structures on the male's phallus are situated in grooves within the bursa copulatrix of the female's reproductive system. The males also have appendages used to grasp and hold the female during copulation. [15]
Similarly to other flies in the family Calliphoridae, P. regina exhibit little or no parental care. Females, however, oviposit their eggs after mating on carrion, leaving the eggs to hatch and develop on their own.
Mature P. regina females are known to oviposit their eggs on animal carcasses following copulation. Interestingly, it has been seen that the olfactory senses of female flies play some role in their decision of where and when to oviposit. Research suggests adult female P. regina will increase their ovipositing in the presence of a medium that provides odor stimuli to the fly. [16]
Black blow fly larvae, like many other blow flies, exhibit the maggot mass effect: a raise in temperature due to the aggregation of maggots. This rise in temperature may be beneficial to the larvae by aiding in feeding and development as well as protection from dangerously cold temperatures, predators, and parasites. Studies with other blow flies suggest that the change in temperature seen in the maggot mass effect functions well at a wide range of temperatures and that the larvae do not reduce their heat production at higher temperatures. [17]
The entire genome of P. regina has been sequenced so that it may serve as a reference genome that can be used in comparison with other Calliphoridae species. This fly has a chromosome number of 2n=12. The sex chromosomes of P. regina are a heteromorphic chromosome pair, meaning they have two morphologically distinct chromosomes that remain a homologous chromosome pair. [18]
Picard and Wells used amplified fragment length polymorphisms (AFLP) to create genetic profiles of P. regina flies collected from different regions to compare both within region and across region relatedness. They discovered adult flies take from the same corpse showed high relatedness, but between regions genetic variability was high. They suggest these findings may be especially important to forensic entomology with respect to determining if a recovered body has moved locations by comparing AFLP data across individual P. regina. [14]
P. regina, like other flies, is poikilothermic: the growth and development of the fly is dependent on temperature. At room temperature, the egg to pupal stage lasts about 6–11 hours. With an increase in temperature of the surrounding environment, metabolic rates of the blow fly typically increase, causing an increase in the rate of growth and development. [19] However, this species is intolerant to warmer temperatures, unlikely to survive to adulthood at temperatures of 40 °C or greater. This observation provides an explanation as to why the species cannot survive the summer months in southern regions of the US. The adult organism's activity becomes inhibited by temperatures lower than 12.5 °C. [4] In addition to an increase in the growth and development, temperature also has a profound impact on female oviposition. [20] It is key to note the fluctuations between diurnal and nocturnal temperatures.
It is important to note the larval stage of the blowfly, due to its importance in forensics. The larvae have posterior spiracles, small openings on the back used for the intake of oxygen. Larvae are also equipped with mouth hooks used for the physical breakdown of proteins when feeding, while proteolytic enzymes are used for chemical breakdown of these proteins. [21]
P. regina larvae have been shown to be an important organism in myiasis of both humans and animals, particularly in the southern region of the United States. Often in a myiatic infection where P. regina larvae are found, they are the only species involved; however, they had been found to be present in a wound with Cochliomyia hominivorax formerly C. americana as well. [22]
P. regina is a very important species in medico-criminal entomology, an area in forensic entomology which uses entomologists to aid with arthropod evidence in criminal investigations. [23] This aspect of forensic science stresses using arthropod evidence in solving crimes, often of a violent nature, through two ideal approaches to estimate post mortem interval (PMI). The first approach accounts for the general succession of arthropod communities, and the second considers environmental influences on the development of arthropods. [23] With knowledge of the regional insect fauna and times of carrion colonization, the insect gathering associated with the remains can be analyzed to determine a window of time in which death took place. PMI is a critical aspect of criminal investigations following recovery of a corpse. PMI relies on an entomologist's ability to correlate the species or stage of development of arthropods, in this case P. regina, to an approximation of the elapsed period between a person's death and the discovery of his/her body. [23]
Blow flies are usually the first insects to colonize a body, frequently within minutes after death. [24] P. regina adults and larvae are attracted to the body because, during decomposition, the remains go through rapid physical, biological, and chemical changes. If a corpse is found, the presence of Dipteran larvae may be used to suggest PMI by estimating the time it would have taken for eggs to have been deposited and larvae to have developed to the stage they were collected, while taking into account environmental factors. Blow flies will lay their eggs on the corpse, usually in a wound, if present, or in any of the natural orifices, and the maggot age can give a date of death accurate to a day or less, and is used in the first few weeks after death. [5]
Research is being conducted to further perfect the dating of a PMI. One study suggests that P. regina occasionally oviposits on carrion at night only when certain conditions are met. [20] A similar study found a combination of artificial lighting, warm temperatures, and the onset of low-pressure atmospheric conditions encourages nocturnal oviposition in P. regina [19] Other studies suggest P. regina preferentially distribute their eggs during the day. Confirming the preference for daytime or nighttime oviposition in P. regina could aid in increasing the accuracy of PMI determination, and the disagreement necessitates more experimentation to investigate this environmental effect. [25]
Phormia regina is a flesh-eating fly not usually used for medical gain. However, the maggots from the black blow fly are used in maggot therapy, a type of biotherapy involving the intentional introduction of live, disinfected maggots into the skin and soft tissue wound of a human or animal for the purpose of selectively cleaning out only the necrotic tissue to promote healing. [26]
A maggot is the larva of a fly ; it is applied in particular to the larvae of Brachycera flies, such as houseflies, cheese flies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and crane flies.
The Calliphoridae are a family of insects in the order Diptera, with almost 1,900 known species. The maggot larvae, often used as fishing bait, are known as gentles. The family is known to be polyphyletic, but much remains disputed regarding proper treatment of the constituent taxa, some of which are occasionally accorded family status.
The common green bottle fly is a blowfly found in most areas of the world and is the most well-known of the numerous green bottle fly species. Its body is 10–14 mm (0.39–0.55 in) in length – slightly larger than a house fly – and has brilliant, metallic, blue-green or golden coloration with black markings. It has short, sparse, black bristles (setae) and three cross-grooves on the thorax. The wings are clear with light brown veins, and the legs and antennae are black. The larvae of the fly may be used for maggot therapy, are commonly used in forensic entomology, and can be the cause of myiasis in livestock and pets. The common green bottle fly emerges in the spring for mating.
Bactrocera tryoni, the Queensland fruit fly, is a species of fly in the family Tephritidae in the insect order Diptera. B. tryoni is native to subtropical coastal Queensland and northern New South Wales. They are active during the day, but mate at night. B. tryoni lay their eggs in fruit. The larvae then hatch and proceed to consume the fruit, causing the fruit to decay and drop prematurely. B. tryoni are responsible for an estimated $28.5 million a year in damage to Australian crops and are the most costly horticultural pest in Australia. Up to 100% of exposed fruit can be destroyed due to an infestation of this fly species. Previously, pesticides were used to eliminate B. tryoni from damaging crops. However, these chemicals are now banned. Thus, experts devoted to B. tryoni control have transitioned to studying this pests' behaviors to determine a new method of elimination.
Chrysomya putoria, also known as the tropical African latrine blowfly, is a fly species belonging to the blowfly family, Calliphoridae.C. putoria is native to Africa and has recently spread to the Americas. These flies pose significant health risks, especially due to their close association with human settlements. Adult flies can carry pathogens, while larvae may cause myiasis by growing and feeding on the flesh of domestic animals and humans. Other myiasis-causing flies in the same genus are C. bezziana and C. megacephala. C. putoria and other flies that feed on decomposing tissue are used as important tools in forensic entomology to establish the post-mortem interval, or the time elapsed since death.
Calliphora vomitoria, known as the blue bottle fly, orange-bearded blue bottle, or bottlebee, is a species of blow fly, a species in the family Calliphoridae. Calliphora vomitoria is the type species of the genus Calliphora. It is common throughout many continents including Europe, Americas, and Africa. They are fairly large flies, nearly twice the size of the housefly, with a metallic blue abdomen and long orange setae on the gena.
Chrysomya is an Old World blow fly genus of the family Calliphoridae. The genus Chrysomya contains a number of species including Chrysomya rufifacies and Chrysomya megacephala. The term “Old World blow fly” is a derivative of both the associated family, Calliphoridae, and the belief that the genus Chrysomya originated in Asia and migrated to North America only relatively recently. Chrysomya’s primary importance to the field of medico-criminal forensic entomology is due to the genus’ reliable life cycle, allowing investigators to accurately develop a postmortem interval. Chrysomya adults are typically metallic colored with thick setae on the meron and plumose arista. The name comes from the word chrysos, meaning “golden” in reference to the metallic sheen of the genus’ species, and -mya, a derivation from the word myia, meaning “fly”.
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 species is the hairy maggot blow fly, and it belongs to the genus Chrysomya, which is commonly referred to as the Old World screwworms. This genus includes other species such as Chrysomya putoria and Chrysomya bezziana, which are agents of myiasis. C. rufifacies prefers very warm weather and has a relatively short lifecycle. It is widely distributed geographically and prefers to colonize large carcasses over small ones. The species commonly has a greenish metallic appearance and is important medically, economically, and forensically.
Forensic entomological decomposition is how insects decompose and what that means for timing and information in criminal investigations. Medicolegal entomology is a branch of forensic entomology that applies the study of insects to criminal investigations, and is commonly used in death investigations for estimating the post-mortem interval (PMI). One method of obtaining this estimate uses the time and pattern of arthropod colonization. This method will provide an estimation of the period of insect activity, which may or may not correlate exactly with the time of death. While insect successional data may not provide as accurate an estimate during the early stages of decomposition as developmental data, it is applicable for later decompositional stages and can be accurate for periods up to a few years.
Lucilia illustris is a member of the fly family Calliphoridae, commonly known as a blow fly. Along with several other species, L. illustris is commonly referred to as a green bottle fly. Lucilia illustris is typically 6–9 mm in length and has a metallic blue-green thorax. The larvae develop in three instars, each with unique developmental properties. The adult fly typically will feed on flowers, but the females need some sort of carrion protein in order to breed and lay eggs.
Calliphora vicina is a member of the family Calliphoridae, which includes blow flies and bottle flies. These flies are important in the field of forensic entomology, being used to estimate the time of a person's death when a corpse is found and then examined. C. vicina is currently one of the most entomologically important fly species for this purpose because it arrives at and colonizes a body following death in consistent timeframes.
The common toad fly, Lucilia silvarum, is a member of the fly family Calliphoridae. This fly was first discovered by Johann Wilhelm Meigen in 1826 and is found most notably in European and Western Countries.
Sarcophaga bullata, or the grey flesh fly, is a species of fly belonging to the family Sarcophagidae. It varies in size from small to large, 8 to 17 millimeters in length and is very similar in appearance and behavior to a closely related species, Sarcophaga haemorrhoidalis. S. bullata is a common scavenger species in the Eastern United States, but is found throughout the Nearctic region. Identification down to the species level in the family Sarcophagidae is notably difficult and relies primarily on the male genitalia. Though limited information is available regarding S. bullata, it has gained increasing recognition in the field of forensic entomology as a forensically relevant fly species, as it may be among the first species to colonize human remains. In these instances, recovered maggots may be analyzed for post-mortem interval (PMI) estimations, which may be used as evidence in courts of law. Current studies regarding S. bullata have revealed a maternal effect operating in these flies that prevents pupal diapause under certain environmental conditions, which is an important factor to be considered during forensic analyses.
Lucilia thatuna belongs to the family Calliphoridae, the species most commonly referred to as the blowflies, and the genus Lucilia. Along with several other species of Lucilia, L. thatuna is commonly referred to as a green bottle fly. L. thatuna is very scarce and not much is known about this particular fly. It has been noted to reside in mountainous regions of the northwestern United States.
Cynomya cadaverina, also known as the shiny blue bottle fly, is a member of the family Calliphoridae, which includes blow flies as well as bottle flies. In recent years, this family has become a forensically important facet in many medicocriminal investigations in the growing field of forensic entomology. C. cadaverina is specifically important in determining a post-mortem interval, as well as other important factors.
Calliphora livida is a member of the family Calliphoridae, the blow flies. This large family includes the genus Calliphora, the "blue bottle flies". This genus is important in the field of forensic entomology because of its value in post-mortem interval estimation.
Lucilia coeruleiviridis, formerly Phaenecia coeruleiviridis, is commonly known as a green bottle fly, because of its metallic blue-green thorax and abdomen. L. coeruleiviridis was first discovered by French entomologist Pierre-Justin-Marie Macquart in 1855. It belongs to the family Calliphoridae and is one of many forensically important Diptera, as it is often found on decaying substances. L. coeruleiviridis is one of the most ubiquitous blow fly species in the southeastern United States, particularly in the spring and fall months.
Protophormia terraenovae is commonly called northern blowfly, blue-bottle fly or blue-assed fly. It is distinguished by its deep blue coloration and large size and is an important species throughout the Northern Hemisphere. This fly is notable for its economic effect as a myiasis pest of livestock and its antibiotic benefits in maggot therapy. Also of interest is P. terraenovae’s importance in forensic investigations: because of their temperature-dependent development and their prominent presence on corpses, the larvae of this species are useful in minimum post-mortem interval (mPMI) determination.
Rhagoletis juglandis, also known as the walnut husk fly, is a species of tephritid or fruit fly in the family Tephritidae. It is closely related to the walnut husk maggot Rhagoletis suavis. This species of fly belongs to the R. suavis group, which has a natural history consistent with allopatric speciation. The flies belonging to this group are morphologically distinguishable.
John G. Stoffolano, Jr. is an American entomologist specializing in non-biting fly behavior, physiology, and veterinary issues of flies as vectors of pathogens.
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