Phormia regina
Encyclopedia
The species Phormia regina, more commonly known as the black blow fly, belongs to the blow fly family Calliphoridae. Although some authorities merge both the blow fly group (Calliphoridae) and the flesh fly group (Sarcophagidae) together in the family Metopiidae, key distinguishable physical traits allow for this separation.
Being a member of the order Diptera
(the fly order), it is attributed by the presence of only its pair of fore wings while the pair of hind wings has been highly reduced to halteres
. These halteres function in aiding in stability and maneuverability during flight. Wings of this fly are specialized having a sharp bend halfway through the wing and they are also known to have a well-developed calypter
. Blow flies are about the size of a house fly or a little larger, many are metallic blue or green. Key characteristics of this species include black gena
, mostly white calypteres and anterior thoracic spiracle
s that appear to be orange yellow due to being surrounded by bright orange setae.
in 1826. Its specific epithet is derived from the Latin
regina 'queen'. Meigen's career works were mainly involved in the taxonomical aspect of identifying different species of diptera. Spending a lot of time classifying species based on wing ventilation as well as, antennae, he discovered that this was not sufficient enough to classify these dipteran species. He then reasoned that species can only identified by combination of characteristics; this technique later became known as the eclectic
method.
e continue feeding throughout three instar
stages until they have stored up enough calories to commence pupation and finally emerge as adult blowflies. 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
.
development in the ovaries in order to produce eggs that are completely mature, and studies show that ovaries in females which have been deprived of a high protein diet will 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; and even then, a lower percentage of those feeding on dung will have fully developed. For instance, an experiment by Stoffolano showed that 100% of females feeding exclusively on beef liver were able to reach the final stage of sexual development after thirteen days, while only 78% of females were able to do so when feeding exclusively on pig dung over a twenty day period. It is also important to note that although some dipteran species will oviposit on dung, Phormia regina oviposits exclusively on carrion
.
Furthermore, 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 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. In this same study by Stoffolano, it is noted that protein is not generally necessary for spermatogenesis in male flies, but that it is paramount for accessory reproductive gland development, higher rates of copulation, and the capability of impregnating females. An additional study by Stoffolano found that there is a positive correlation between male head size and the size of the aedeagi (the external reproductive organs), which has been suggested as a possible reason for lower percentages of insemination between small males and large females within this species.
Because the larval lifecycle 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 and those that are able to pupate do not emerge as adults. The lowest temperature threshold for this species was found to be 12.5°C and below; females will not oviposit at these temperatures. The highest rate of development (with survival) in a study by Byrd and Allen was a constant temperature of 35°C where the average time of adult emergence was 265 hours (about 11 days). Constant temperatures between 15 to 30°C (at 5 degree increments) developed slower, with the coolest temperatures taking 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 was collected by placing specimens in an incubator which steadily alternated between the maximum and minimum temperatures of a particular ten degree range (e.g. 25 to 35°C). Each ten degree fluctuation took place over a twelve hour time span.)
Also, there have been studies to detect the effects of light exposure on developmental variability in larvae. These studies have shown that 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, the variations in light photoperiods mentioned above had no effect on pupal duration times.
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 that are used for the intake of oxygen. Larvae are also equipped with mouth hooks that are used for the breakdown of proteins when feeding. Another mechanism used for the breakdown of these proteins is the proteolytic enzyme
.
which involves the calling upon of entomologists to aid with arthropod evidence in criminal investigations. This aspect of forensic science stresses utilizing arthropod evidence in solving crimes most often of a violent nature using two ideal approaches. One approach takes into account the general succession of arthropod communities to aid in estimation of post mortem interval, and the second factors in environmental influences in the development of arthropods. 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. The time elapsed since death before a corpse is discovered, referred to as post mortem interval or PMI, is critical for investigations. Post mortem interval relies on an entomologist’s ability to correlate the species or stage of development of arthropods, in this case Phormia regina, to an approximation of the elapsed period between a person's death and the discovery of his/her body.
Blow flies are usually the first insects to colonize a body, frequently within minutes after death. Phormia 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 early stages of diptera present may be used in determining the post mortem interval by reverse estimation of the time it would take for eggs to have been deposited and larvae to have developed to the stage they were collected, while taking into account environmental factors. The use of maggot
age and development can give a date of death accurate to a day or less and is used in the first few weeks after death. Blow flies will lay their eggs on the corpse, usually in a wound, if present, or in any of the natural orifices. Therefore, after a single blowfly generation has been completed, the time of death is determined using the first method, that of insect succession.
Research is being conducted to further perfect the dating of a post mortem interval
. A study done by Greenberg suggests that Phormia regina occasionally oviposit on carrion during nocturnal hours only when certain conditions are met. A similar study performed in Central Texas (Kirkpatrick 2004) found that a combination of artificial lighting, warm temperatures, and the onset of low-pressure atmospheric conditions encourages nocturnal oviposition in Phormia regina This knowledge of the effects of nocturnal temperatures on blow fly occurrence and oviposition behavior will lead to more accurate estimates of the post mortem interval related to deaths, therefore, an abundance of research is needed in order to assign a precise PMI.
is a type of biotherapy involving the intentional introduction by a health care practitioner of live, disinfected maggots into the non-healing skin and soft tissue wound of a human or animal for the purpose of selectively cleaning out only the necrotic tissue within a wound in order to promote wound healing. Maggot therapy dates back to the Mayan empire, but there are no actual records of use until the early sixteenth century.
The use of black blow fly maggots in maggot therapy is a very common practice. After the maggots have hatched they are carefully monitored until they reach roughly two to three millimeters in length; at this point they are ready for the next step. Within 24 to 36 hours of hatching the maggots are tested for their sterility and if they pass the rigorous tests then they may be used in maggot therapy. These maggots are placed onto a sterile piece of gauze
which is laid over the wound of the patient. The maggots will proceed through the gauze to the open wound, where they will then begin their work. When they are full grown, they leave the wound and enter the gauze for the purpose of pupating. They are then removed with the waste gauze and disposed of properly.
The use of maggot therapy is not limited to humans, but it is not a common practice with livestock. Using maggot therapy with livestock could be beneficial in many ways. In dairy cattle it would eliminate the need to destroy milk contaminated with antibiotics. The use of antibiotics on horses can affect its gastrointestinal flora
which may result in colitis
. Maggot therapy would eliminate this additional stress when treating equine wounds. Treatment options for people who cannot afford expensive surgeries would be a new possibility for veterinarians using unique maggot therapy.
Being a member of the order Diptera
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
(the fly order), it is attributed by the presence of only its pair of fore wings while the pair of hind wings has been highly reduced to halteres
Halteres
Halteres are small knobbed structures modified from the hind wings in some two-winged insects. They are flapped rapidly and function as gyroscopes, informing the insect about rotation of the body during flight....
. These halteres function in aiding in stability and maneuverability during flight. Wings of this fly are specialized having a sharp bend halfway through the wing and they are also known to have a well-developed calypter
Calypter
A calypter is either of two posterior lobes of the posterior margin of the forewing of flies between the extreme posterior wing base and the alula, which covers the halteres....
. Blow flies are about the size of a house fly or a little larger, many are metallic blue or green. Key characteristics of this species include black gena
GENA
GENA stands for General Event Notification Architecture.GENA Base defines an HTTP notification architecture that transmits notifications between HTTP resources. An HTTP resource could be any object which might need to send or receive a notification, for example a distribution list, buddy list,...
, mostly white calypteres and anterior thoracic spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s that appear to be orange yellow due to being surrounded by bright orange setae.
Taxonomy
Phormia regina was described by the German entolomogist Johann Wilhelm MeigenJohann Wilhelm Meigen
Johann Wilhelm Meigen was a German entomologist famous for his pioneering work on Diptera.-Early years:Meigen was born in Solingen, the fifth of eight children of Johann Clemens Meigen and Sibylla Margaretha Bick. His parents, though not poor, were not wealthy either. The ran a small shop in...
in 1826. Its specific epithet is derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
regina 'queen'. Meigen's career works were mainly involved in the taxonomical aspect of identifying different species of diptera. Spending a lot of time classifying species based on wing ventilation as well as, antennae, he discovered that this was not sufficient enough to classify these dipteran species. He then reasoned that species can only identified by combination of characteristics; this technique later became known as the eclectic
Eclecticism
Eclecticism is a conceptual approach that does not hold rigidly to a single paradigm or set of assumptions, but instead draws upon multiple theories, styles, or ideas to gain complementary insights into a subject, or applies different theories in particular cases.It can sometimes seem inelegant or...
method.
Life cycle and development
The life cycle and development of Phormia regina is similar to that of most other dipteran species, in which females oviposit their eggs into a nutrient substrate and after eclosion (i.e. hatching), the larvaLarva
A larva 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...
e continue feeding throughout three instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
stages until they have stored up enough calories to commence pupation and finally emerge as adult blowflies. Each transition from first, second, and third instar is marked by a molt and eventually the third instar larvae develop sclerotized
Sclerite
A sclerite is a hardened body part. The term is used in various branches of biology for various structures including hardened portions of sponges, but it is most commonly used for the hardened portions of arthropod exoskeletons....
(hardened) casings which envelop and protect them throughout metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
.
Adult development
While, in the wild, dung constitutes a majority of the nutritional intake utilized for sexual maturity development in both male and female adults within this species, studies have shown that diets consisting of higher protein content will better facilitate mating conditions of both sexes. Female sexual maturity requires the completion of ten stages of follicleOvarian follicle
Ovarian follicles are the basic units of female reproductive biology, each of which is composed of roughly spherical aggregations of cells found in the ovary. They contain a single oocyte . These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single...
development in the ovaries in order to produce eggs that are completely mature, and studies show that ovaries in females which have been deprived of a high protein diet will 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; and even then, a lower percentage of those feeding on dung will have fully developed. For instance, an experiment by Stoffolano showed that 100% of females feeding exclusively on beef liver were able to reach the final stage of sexual development after thirteen days, while only 78% of females were able to do so when feeding exclusively on pig dung over a twenty day period. It is also important to note that although some dipteran species will oviposit on dung, Phormia regina oviposits exclusively on carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...
.
Furthermore, 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 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. In this same study by Stoffolano, it is noted that protein is not generally necessary for spermatogenesis in male flies, but that it is paramount for accessory reproductive gland development, higher rates of copulation, and the capability of impregnating females. An additional study by Stoffolano found that there is a positive correlation between male head size and the size of the aedeagi (the external reproductive organs), which has been suggested as a possible reason for lower percentages of insemination between small males and large females within this species.
Larval development
There have been relatively few studies conducted on the adults of this species in comparison to those on larval development. This is mostly due to the importance of blowfly larvae in determining the post mortem interval (PMI) of corpses during investigations by forensic entomologists. For this reason, many researchers have done studies to discover how various environmental factors will affect the duration time of larval development in this species (as well as many others).Because the larval lifecycle of this species is dependent on a climate with temperatures ranging from 12.7°C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
(55°F
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...
) 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 and those that are able to pupate do not emerge as adults. The lowest temperature threshold for this species was found to be 12.5°C and below; females will not oviposit at these temperatures. The highest rate of development (with survival) in a study by Byrd and Allen was a constant temperature of 35°C where the average time of adult emergence was 265 hours (about 11 days). Constant temperatures between 15 to 30°C (at 5 degree increments) developed slower, with the coolest temperatures taking 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 was collected by placing specimens in an incubator which steadily alternated between the maximum and minimum temperatures of a particular ten degree range (e.g. 25 to 35°C). Each ten degree fluctuation took place over a twelve hour time span.)
Also, there have been studies to detect the effects of light exposure on developmental variability in larvae. These studies have shown that 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, the variations in light photoperiods mentioned above had no effect on pupal duration times.
Physiology
Like most other flies the blowfly feeds via sponging, having functional or non-functional mouthparts. They are known to feed on various foods, with emphasis on nectar, honey-dew, and the liquid products of decomposition. Phormia 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 approximately 6–11 hours. When there is an increase in temperature of the surrounding environment, typically metabolic rates of the blow fly increase, causing an increase in the rate of growth and development. In addition to an increase in the growth and development, temperature also has a profound impact on female oviposition. It is key to note the fluctuations between diurnal and nocturnal temperatures. Typically blow flies will oviposit in the daytime due to the increase of temperature.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 that are used for the intake of oxygen. Larvae are also equipped with mouth hooks that are used for the breakdown of proteins when feeding. Another mechanism used for the breakdown of these proteins is the proteolytic enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
.
Forensic importance
Phormia regina is a very important species in medicocriminal entomology, an area in forensic entomologyForensic entomology
Forensic entomology is the application and study of insect and other arthropod biology to criminal matters. It is primarily associated with death investigations; however, it may also be used to detect drugs and poisons, determine the location of an incident, and find the presence and time of the...
which involves the calling upon of entomologists to aid with arthropod evidence in criminal investigations. This aspect of forensic science stresses utilizing arthropod evidence in solving crimes most often of a violent nature using two ideal approaches. One approach takes into account the general succession of arthropod communities to aid in estimation of post mortem interval, and the second factors in environmental influences in the development of arthropods. 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. The time elapsed since death before a corpse is discovered, referred to as post mortem interval or PMI, is critical for investigations. Post mortem interval relies on an entomologist’s ability to correlate the species or stage of development of arthropods, in this case Phormia regina, to an approximation of the elapsed period between a person's death and the discovery of his/her body.
Blow flies are usually the first insects to colonize a body, frequently within minutes after death. Phormia regina adults and larvae are attracted to the body because during decomposition
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
, the remains go through rapid physical, biological, and chemical changes. If a corpse is found, the early stages of diptera present may be used in determining the post mortem interval by reverse estimation of the time it would take for eggs to have been deposited and larvae to have developed to the stage they were collected, while taking into account environmental factors. The use of maggot
Maggot
In everyday speech the word maggot means the larva of a fly ; it is applied in particular to the larvae of Brachyceran flies, such as houseflies, cheese flies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and Crane flies...
age and development can give a date of death accurate to a day or less and is used in the first few weeks after death. Blow flies will lay their eggs on the corpse, usually in a wound, if present, or in any of the natural orifices. Therefore, after a single blowfly generation has been completed, the time of death is determined using the first method, that of insect succession.
Research is being conducted to further perfect the dating of a post mortem interval
Post mortem interval
Post-mortem interval is the time that has elapsed since a person has died. If the time in question is not known, a number of medical/scientific techniques are used to determine it. This also can refer to the stage of decompostion the person is in....
. A study done by Greenberg suggests that Phormia regina occasionally oviposit on carrion during nocturnal hours only when certain conditions are met. A similar study performed in Central Texas (Kirkpatrick 2004) found that a combination of artificial lighting, warm temperatures, and the onset of low-pressure atmospheric conditions encourages nocturnal oviposition in Phormia regina This knowledge of the effects of nocturnal temperatures on blow fly occurrence and oviposition behavior will lead to more accurate estimates of the post mortem interval related to deaths, therefore, an abundance of research is needed in order to assign a precise PMI.
Medicinal importance
Phormia regina is a flesh-eating fly not usually used for medical gain. However, the maggots from the black blow fly are used in a medical practice called maggot therapy. Maggot therapyMaggot therapy
Maggot therapy is a type of biotherapy involving the intentional introduction of live, disinfected maggots into the non-healing skin and soft tissue wound of a human or animal for the purpose of cleaning out the...
is a type of biotherapy involving the intentional introduction by a health care practitioner of live, disinfected maggots into the non-healing skin and soft tissue wound of a human or animal for the purpose of selectively cleaning out only the necrotic tissue within a wound in order to promote wound healing. Maggot therapy dates back to the Mayan empire, but there are no actual records of use until the early sixteenth century.
The use of black blow fly maggots in maggot therapy is a very common practice. After the maggots have hatched they are carefully monitored until they reach roughly two to three millimeters in length; at this point they are ready for the next step. Within 24 to 36 hours of hatching the maggots are tested for their sterility and if they pass the rigorous tests then they may be used in maggot therapy. These maggots are placed onto a sterile piece of gauze
Gauze
Gauze is a thin, translucent fabric with a loose open weave.-Uses and types:Gauze was originally made of silk and was used for clothing. It is now used for many different things, including gauze sponges for medical purposes. When used as a medical dressing, gauze is generally made of cotton...
which is laid over the wound of the patient. The maggots will proceed through the gauze to the open wound, where they will then begin their work. When they are full grown, they leave the wound and enter the gauze for the purpose of pupating. They are then removed with the waste gauze and disposed of properly.
The use of maggot therapy is not limited to humans, but it is not a common practice with livestock. Using maggot therapy with livestock could be beneficial in many ways. In dairy cattle it would eliminate the need to destroy milk contaminated with antibiotics. The use of antibiotics on horses can affect its gastrointestinal flora
Flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...
which may result in colitis
Colitis
In medicine, colitis refers to an inflammation of the colon and is often used to describe an inflammation of the large intestine .Colitides may be acute and self-limited or chronic, i.e...
. Maggot therapy would eliminate this additional stress when treating equine wounds. Treatment options for people who cannot afford expensive surgeries would be a new possibility for veterinarians using unique maggot therapy.
Further reading
- Anderson, G.S. Forensic Entomology: the use of insects in death investigations.
- Byrd, J.H. and J.C. Allen. 2001. The development of the black blow fly, Phormia regina (Meigen). Forensic Sci. Int. 120: 79-88.
- Byrd, J. H., and J. L. Castner. 2001. Forensic entomology : The utility of arthropods in legal investigations. CRC Press, New York.
- Catts, E. P., and M. L. Goff. 1992. Forensic entomology in criminal investigations. Ann. Rev. Entomol. 37 : 253-272.
- Fletcher F., Haub J.G. Digestions in blowfly larvae, Phormia regina meigen, used in the treatment of osteomyelitis. Ohio State University.
- Greenberg, B. 1990. Nocturnal oviposition behavior of blow flies (Diptera: Calliphoridae). J. Med. Entomol. 27 (5) : 807-810.
- Kirkpatrick, R. S. Nocturnal light and temperature influences on necrophagous, carrion-associatingblow fly species of forensic importance in Central Texas. TAMU Undergrad. J. Sci.
- Nabity, P.D., L.G. Higley, and T.M. Heng-Moss. 2007. Light-Induced Variability in Development of Forensically Important Blow Fly Phormia regina (Diptera: Calliphoridae). J. Med. Entomol. 44(2): 351-358.
- Rognes, Knut. 1991. Blowflies (Diptera, Calliphoridae) of Fennoscandia and Denmark. E.J. Brill/Scandinavian Science Ltd., 272pp.
- Stoffolano, J.G. Jr, E.Y. Gonzalez, M. Sanchez, J Kane, K Velázquez, A.L. Oquendo, G. Sakolsky, P. Schafer, and C.-M. Yin. 2000. Relationship Between Size and Mating Success in the Blow Fly Phormia regina (Diptera: Calliphoridae). Ann. Entomol. Soc. Am. 93(3): 673-677.
- Stoffolano, J.G. Jr, M.-F. Li, J.A. Sutton Jr, and C.-M. Yin. 1995. Faeces feeding by adult Phormia regina (Diptera: Calliphoridae): impact on reproduction. Medical and Veterinary Entomology 9, 388-392.
- Watson L., Dallwitz M.J., British Insects: the Families of Diptera.
- Whitworth, Terry. 2006. Keys to the Genera and Species of the Blow Flies (Diptera:Calliphoridae) of America North of Mexico. PROC. ENTOL. SOC. WASH. 30 June. 108(3), pp. 629–725