Entomotoxicology
Encyclopedia
In forensic entomology
, entomotoxicology is the analysis of toxins in arthropod
s (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.
, 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.
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. Morphine and heroin were both believed to slow down the rate of fly development. 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. Cocaine and methamphetamine also accelerate the rate of fly development.
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”. 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.
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.
, 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.
, 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.
, 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. 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.
, 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.
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 feed in the woman’s nasal cavity. Research revealed that maggot development can be sped up by the ingestion of cocaine.
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, doxycyline, 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 for investigators to detect toxins in a body years after death
.
, 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. 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. 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.
Forensic 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...
, entomotoxicology is the analysis of toxins in arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s (mainly flies
Fließ
Fließ is a municipality in the Landeck district and is located5 km south of Landeck on the upper course of the Inn River. It has 9 hamlets and was already populated at the roman age; the village itself was founded around the 6th century. After a conflagration in 1933 Fließ was restored more...
and beetles) that feed 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...
. 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.
Effects of toxins on arthropods
Drugs can have a variety of effects on development rates of arthropods. MorphineMorphine
Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...
, heroin, cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...
, and methamphetamine
Methamphetamine
Methamphetamine is a psychostimulant of the phenethylamine and amphetamine class of psychoactive drugs...
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
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...
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
Diptera
Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...
) are the most commonly used insect in entomotoxicology.
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. Morphine and heroin were both believed to slow down the rate of fly development. 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. Cocaine and methamphetamine also accelerate the rate of fly development.
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”. 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.
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.
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. 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 decompositionDecomposition
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...
, 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
Phenobarbital
Phenobarbital or phenobarbitone is a barbiturate, first marketed as Luminal by Friedr. Bayer et comp. It is the most widely used anticonvulsant worldwide, and the oldest still commonly used. It also has sedative and hypnotic properties but, as with other barbiturates, has been superseded by the...
was detected and perceived to have been in the woman’s system upon death.
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. TriazolamTriazolam
Triazolam is a benzodiazepine drug. It possesses pharmacological properties similar to that of other benzodiazepines, but it is generally only used as a sedative to treat severe insomnia...
, 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.
Aid determination of origin
Pekka Nuorteva presented the case of a young woman found severely decomposed in Inkoo, Finland. Diptera larvae recovered from the body were reared to adulthood and found to contain low levels of mercuryMercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
, 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. This case applied Nuorteva’s research involving mercury and its effect on maggots. Through experimentation, it was determined that maggots (fed on fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
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.
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 rufifaciesChrysomya rufifacies
Chrysomya rufifacies is a species belonging to the blow fly family, Calliphoridae, and is most significant in the field of forensic entomology due to its use in establishing or altering postmortem intervals. The common name for the species is the hairy maggot blow fly, and it belongs to the genus...
, found on the corpse and tissue samples from the body revealed malathion
Malathion
Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity, however one recent study has shown that children with higher levels of organophosphate pesticide metabolites in their urine are more likely...
. 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
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...
malathion in the man’s system delayed oviposition for a few days.
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 feed in the woman’s nasal cavity. Research revealed that maggot development can be sped up by the ingestion of cocaine.
Use of shed casings and insect feces
Not only are tissues from maggots used to detect toxins, shed casings and insect feces 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 examinerMedical examiner
A medical examiner is a medically qualified government officer whose duty is to investigate deaths and injuries that occur under unusual or suspicious circumstances, to perform post-mortem examinations, and in some jurisdictions to initiate inquests....
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
Ampicillin
Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci...
, Ceclor, doxycyline, erythromycin
Erythromycin
Erythromycin is a macrolide antibiotic that has an antimicrobial spectrum similar to or slightly wider than that of penicillin, and is often used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma and...
, Elavil, Lomotil
Lomotil
The drug combination diphenoxylate/atropine is a popular oral anti-diarrheal in the United States, manufactured by Pfizer. Its UK BAN generic name is co-phenotrope....
, pentazocine
Pentazocine
Pentazocine is a synthetically prepared prototypical mixed agonist-antagonist narcotic drug of the benzomorphan class of opioids used to treat moderate to moderately severe pain...
, and Tylenol 3. McDonough performed toxicological analyses on stomach contents and dried sections of brain and found lethal levels of amitriptyline
Amitriptyline
Amitriptyline is a tricyclic antidepressant . It is the most widely used TCA and has at least equal efficacy against depression as the newer class of SSRIs...
and nortriptyline
Nortriptyline
Nortriptyline is a second-generation tricyclic antidepressant marketed as the hydrochloride salt under the trade names Sensoval, Aventyl, Pamelor, Norpress, Allegron, Noritren and Nortrilen. It is used in the treatment of major depression and childhood nocturnal enuresis...
. Insect feces, shed pupal cases of Megaselia scalaris
Megaselia scalaris
The fly Megaselia scalaris is a member of the order Diptera and the family Phoridae. The family members are commonly known as the "humpbacked fly", the "coffin fly", and the "scuttle fly". The name "scuttle fly" derives from the jerky, short bursts of running, characteristic to the adult fly...
(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 for investigators to detect toxins in a body years after death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
.
Limitations
Further research should be conducted in order to fill the gaps in entomotoxicology. Such areas as bioaccumulationBioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
, insect metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
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. 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. demonstrated this theory using Calliphora vicina
Calliphora vicina
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. C. vicina is currently one of the most entomologically important fly species because of its consistent time of arrival and...
larvae reared on human skeletal muscle obtained from cases of co-proxamol and amitriptyline
Amitriptyline
Amitriptyline is a tricyclic antidepressant . It is the most widely used TCA and has at least equal efficacy against depression as the newer class of SSRIs...
overdose. Samples of pupae and third 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...
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.