Entomotoxicology

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In forensic entomology, entomotoxicology is the analysis of toxins in arthropods (mainly flies and beetles) that feed on carrion. Using arthropods in a corpse or at a crime scene, investigators can determine whether toxins were present in a body at the time of death. This technique is a major advance in forensics; previously, such determinations were impossible in the case of severely decomposed bodies devoid of intoxicated tissue and bodily fluids. Ongoing research into the effects of toxins on arthropod development has also allowed better estimations of postmortem intervals.

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Effects of toxins on arthropods

Drugs can have a variety of effects on development rates of arthropods. Morphine, heroin, cocaine, and methamphetamine are commonly involved in cases where forensic entomology is used. The stages of growth for insects provides a basis for determining a cause in altered cycles in a specific species. An altered stage in development can often indicate toxins in the carrion on which the insects are feeding. Beetles (Order: Coleoptera) and beetle feces are often used in entomotoxicology, but the presence of toxins is often the result of the beetles' feeding on fly larvae that have been feeding on the carrion containing toxic substances. Flies (Order: Diptera) are the most commonly used insect in entomotoxicology. [1]

Through the study of Sarcophaga (Curranea) tibialis larvae, barbiturates were found to increase the length of the larval stage of the fly, which will ultimately cause an increase in the time it takes to reach the stage of pupation. [2] Morphine and heroin were both believed to slow down the rate of fly development. [3] [4] However, closer examination of the effects of heroin on fly development has shown that it actually speeds up larval growth and then decreases the development rate of the pupal stage. This actually increases the overall timing of development from egg to adult. Research of Lucilia sericata (Diptera: Calliphoridae), reared on various concentrations of morphine injected meat, found higher concentrations of morphine in shed pupal casings than in adults. [5] Cocaine and methamphetamine also accelerate the rate of fly development. [3]

Some effects depend on the concentration of the toxin while others simply depend on its presence. For example, cocaine (at the lethal dose) causes larvae to “develop more rapidly 36 (to 76) hours after hatching”. [3] The amount of growth depends on the concentration of cocaine in the area being fed upon. The amount of methamphetamine, on the other hand, affects the rate of pupal development. A lethal dose of methamphetamine increases larval development through approximately the first two days and afterwards the rate drops if exposure remains at the median lethal dosage. The presence of methamphetamine was also found to cause a decrease in the maximum length of the larvae. [3]

Along with changes in development rates, extended periods of insect feeding refrain and variation in the size of the insect during any stage of development, can also indicate the presence of toxic substances in the insect's food source. [3]

Examples of use

Since J.C. Beyer and his partners first demonstrated the ability of toxins to be recovered from maggots feeding on human remains in 1980, the use of entomotoxicology in investigations has made an emergence into the field of forensic entomology. [6] An example of one such case involved the discovery of a 22-year-old female with a history of suicide attempts found 14 days after her death. Due to the body's advanced stage of decomposition, no organ or tissue samples were viable to screen for toxins. Through gas chromatography (GC) and thin-layer chromatography (TLC) analysis of Cochliomyia macellaria (Diptera: Calliphoridae) larvae found feeding on the woman's body, phenobarbital was detected and perceived to have been in the woman's system upon death. [3]

Drug abuse detected

In France, Pascal Kintz and his colleagues were able to demonstrate the use of entomotoxicology to detect toxins that were not discovered during the analysis of body tissues and fluids of a body found roughly two months after death. A liquid chromatography analysis on organ tissue and Calliphoridae larvae found at the scene revealed the existence of five prescription medications. Triazolam, however, was only detected in the analysis of maggots and not in organ tissue samples. Comparative research showed increased sensitivity of toxicological analysis of Diptera samples over decomposed body tissues. A similar case involved the discovery of the remains of a 29-year-old known to abuse drugs, last seen alive five months prior. Through the use of GC and GC-MS techniques, Nolte and his partners discovered the presence of cocaine in decomposed muscle tissue and in maggots found on the body. However, due to the severity of decomposition of the muscle tissue, more suitable drug samples (devoid of decomposition byproducts) were reared from the maggots. [3]

Aid determination of origin

Pekka Nuorteva presented the case of a young woman found severely decomposed in Ingå, Finland. Diptera larvae recovered from the body were reared to adulthood and found to contain low levels of mercury, indicating that the woman came from an area of comparatively low mercury pollution. This assumption was proven correct once the woman was identified and found to have been a student in Turku, Finland. This case demonstrated the ability of toxicological analysis to help determine origin. [7] This case applied Nuorteva's research involving mercury and its effect on maggots. Through experimentation, it was determined that maggots (fed on fish containing mercury) possessed levels of mercury in their tissue of even greater concentration than in the tissue of the fish. Nuorteva also discovered that the presence of mercury in the maggots systems hindered their ability to enter into the pupal stage. [8]

Toxin confounding of postmortem interval estimate

Through the analysis of specific cases, it was revealed that toxins present in a person's body upon death can confound postmortem interval estimations. An example of such a case, reported by Gunatilake and Goff, concerned the discovery of a 58-year-old male with a history of attempted suicides found dead in a crawl space in Honolulu, Hawaii last seen eight days prior. Two species of Diptera (Calliphoridae), Chrysomya megacephala and Chrysomya rufifacies , found on the corpse and tissue samples from the body revealed malathion. Investigators found it abnormal that, given the conditions, there were only two fly species found on the body and that these species revealed a postmortem interval of five days. Thus it was determined that the presence of the organophosphate malathion in the man's system delayed oviposition for a few days. [7]

Paul Catts analyzed a case in Spokane, Washington where maggots rendered differing postmortem estimations. A 20-year-old female victim was found stabbed to death and laying in an open environment surrounded by trees. Most of the oldest maggots found on the body were approximately 6–7 mm long which suggested that they were roughly seven days old. There was, however, a very strange exception which was the retrieval of a 17.7 mm maggot which suggested an age of 3 weeks. After ruling out the possibility that the maggot had traveled onto the corpse from carrion nearby, it was assumed that there was no conceivable way a 3-week-old maggot could have been present on the corpse. Later investigations revealed that the woman had snorted cocaine shortly before her death and that the 17.7 mm maggot must have fed in the woman's nasal cavity. Research revealed that maggot development can be sped up by the ingestion of cocaine. [9]

Use of shed casings and insect faeces

Not only are tissues from maggots used to detect toxins, shed casings and insect faeces have also been used to detect and identify toxins present in corpses upon death. An instance of this finding was demonstrated by Edward McDonough, a medical examiner in Connecticut. A mummified corpse of a middle-aged woman was found inside of her home. Prescription medicine bottles were found with labels identifying the following drugs: ampicillin, Ceclor, doxycycline, erythromycin, Elavil, Lomotil, pentazocine, and Tylenol 3. McDonough performed toxicological analyses on stomach contents and dried sections of brain and found lethal levels of amitriptyline and nortriptyline. Insect feces, shed pupal cases of Megaselia scalaris (Diptera: Phoridae), and shed larval skins of Dermestes maculates (Coleoptera: Dermestidae) were gathered from the corpse at the scene. McDonough sent these to an FBI lab which broke down the complex structures of the samples using strong acids and bases and freed the toxins for analysis. The cast pupal cases and larval skins were also found to contain amitriptyline and nortriptyline. Larger concentrations were discovered in the pupal cases because phorid flies prefer to feed on softer tissues. The hide beetle larval skins revealed lower concentrations of the drugs because these beetles prefer to feed on dry, mummified bodies. The use of pupal cases and larval skins allows investigators to detect toxins in a body years after death. [8]

Limitations

Further research should be conducted in order to fill the gaps in entomotoxicology. Such areas as bioaccumulation, insect metabolism of drugs, and quantitative analyses of insect evidence have only begun to be researched. Because it is a relatively new branch of forensic entomology, entomotoxicology has its limitations. According to Pounder's research, there is no correlation between the drug concentration in tissue and the larvae feeding on that tissue. [6] Entomological specimens make for excellent qualitative toxicological specimens. There is, however, a lack of research in the way of developing an assessment that can quantify the concentration of a drug in tissue using entomological evidence. One reason for this is that a drug can only be detected in larvae when the rate of absorption exceeds the rate of elimination. [3] [10] demonstrated this theory using Calliphora vicina larvae reared on human skeletal muscle obtained from cases of co-proxamol and amitriptyline overdose. Samples of pupae and third instar larvae no longer contained concentrations of the drugs, suggesting that drugs do not bioaccumulate over the entire life-cycle of larvae. This leads entomologists to theorize that toxins are eliminated from the larvae's system over time if they are not receiving a constant supply of the toxin. [3]

Related Research Articles

<span class="mw-page-title-main">Forensic entomology</span> Application of insect and other arthropod biology to forensics

Forensic entomology is the scientific study of the colonization of a dead body by arthropods. This includes the study of insect types commonly associated with cadavers, their respective life cycles, their ecological presences in a given environment, as well as the changes in insect assemblage with the progression of decomposition. Insect succession patterns are identified based on the time a given species of insect spends in a given developmental stage, and how many generations have been produced since the insects introduction to a given food source. Insect development alongside environmental data such as temperature and vapor density, can be used to estimate the time since death, due to the fact that flying insects are attracted to a body immediately after death. The identification of postmortem interval to aid in death investigations is the primary scope of this scientific field. However, forensic entomology is not limited to homicides, it has also been used in cases of neglect and abuse, in toxicology contexts to detect the presence of drugs, and in dry shelf food contamination incidents. Equally, insect assemblages present on a body, can be used to approximate a given location, as certain insects may be unique to certain areas. Therefore, forensic entomology can be divided into three subfields: urban, stored-product and medico-legal/medico-criminal entomology.

<span class="mw-page-title-main">Histeridae</span> Family of beetles

Histeridae is a family of beetles commonly known as clown beetles or hister beetles. This very diverse group of beetles contains 3,900 species found worldwide. They can be easily identified by their shortened elytra that leaves two of the seven tergites exposed, and their geniculate (elbowed) antennae with clubbed ends. These predatory feeders are most active at night and will fake death if they feel threatened. This family of beetles will occupy almost any kind of niche throughout the world. Hister beetles have proved useful during forensic investigations to help in time of death estimation. Also, certain species are used in the control of livestock pests that infest dung and to control houseflies. Because they are predacious and will even eat other hister beetles, they must be isolated when collected.

<span class="mw-page-title-main">Common green bottle fly</span> Species of insect

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.

<i>Chrysomya putoria</i> Species of fly

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.

<i>Calliphora vomitoria</i> Species of fly

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.

<i>Chrysomya</i> Genus of flies

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”.

<i>Chrysomya rufifacies</i> Species of 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.

<i>Lucilia illustris</i> Species of insect

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.

<i>Phormia regina</i> Species of fly

Phormia regina, the black blow fly, belongs to the blow fly family Calliphoridae and was first described by Johann Wilhelm Meigen.

<i>Chrysomya albiceps</i> Species of fly

Chrysomya albiceps is a species belonging to the blow fly family, Calliphoridae.

<i>Chrysomya megacephala</i> Species of fly

Chrysomya megacephala, more commonly known as the oriental latrine fly or oriental blue fly, is a member of the family Calliphoridae (blowflies). It is a warm-weather fly 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, and also infects fish and livestock.

<i>Chrysomya bezziana</i> Species of fly

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 fly is widely distributed in Asia, tropical Africa, India, and Papua New Guinea. The adult can be identified as metallic green or blue with a yellow face and the larvae are smooth, lacking any obvious body processes except on the last segment.

<i>Lucilia silvarum</i> Species of fly

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.

<i>Sarcophaga bullata</i> Species of fly

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.

<i>Cynomya cadaverina</i> Species of fly

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.

<i>Calliphora livida</i> Species of fly

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.

<i>Lucilia coeruleiviridis</i> Species of fly

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.

<i>Protophormia terraenovae</i> Species of fly

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.

<i>Calliphora stygia</i> Species of fly

Calliphora stygia, commonly known as the brown blowfly, or rango tumaro in Māori, is a species of blow-fly that is found in Australia and New Zealand. The brown blowfly has a grey thorax and yellow-brown abdomen.

References

  1. ↑ Gagliano-Candela, R. and Aventaggiato, L. "The detection of toxic substances in entomological specimens." International Journal of Legal Medicine 114 (2001): 197-203.
  2. ↑ Musvasva, E. and others. "Preliminary observations of the effects of hydrocortisone and sodium methohexital on development of Sarcophaga (Curranea) tibialis Macquart (Diptera: Sarcophagidae), and implications for estimating post mortem interval.” Forensic Science International 120 (2001): 37-41.
  3. 1 2 3 4 5 6 7 8 9 Introna, Francesco and others. ”Entomotoxicology.” Forensic Science International 120 (2001): 42-47.
  4. ↑ Carvalho, Lucila M.L.; Linhares, Arício X.; and Trigo, José Roberto. "Determination of drug levels and effect of diazepam on the growth of necrophagous flies of forensic importance in southeastern Brazil." Forensic Science International 120 (2001): 140-144.
  5. ↑ Bourel, Benoit and others. “Morphine extraction in necrophagous insects remains for determining ante-mortem opiate intoxication.” Forensic Science International 120 (2001): 127-131.
  6. 1 2 Pounder, Derrick J. "Forensic entomo-toxicology." Journal of the Forensic Science Society 31 (1991): 469-472.
  7. 1 2 Goff, M. Lee and Lord, Wayne D. "Entomotoxicology- A New Area for Forensic Investigation." The American Journal of Forensic Medicine and Pathology 15 (1994): 51-57.
  8. 1 2 Goff, M. Lee. A Fly for the Prosecution. Cambridge: Harvard University Press, 2000.
  9. ↑ Catts, E. Paul, and Neal H. Haskell. Entomology and Death: A Procedural Guide. Clemson: Joyce's Print Shop, Inc., 1990.
  10. ↑ Wilson, Z.; Hubbard, S.; Pounder, D.J. "Drug analysis in fly larvae." The American Journal of Forensic Medicine and Pathology 14 (1993): 118-120.
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