The objective of this research was to explore the succession pattern and abundance of carrion insects on decomposing pig carcasses, and the influence of environmental variables and poison on these processes. Conducted in a secluded area of the University of Ibadan stadium, this study used two domestic pigs, Sus scrofa, as surrogate human models. One pig was euthanized using Sniper insecticide, a common suicide agent, while the other was sacrificed without poison, serving as a control experiment.
The carcasses were left to decay until the dry stage, with observations made throughout the five stages of decomposition: fresh, bloat, active decay, advanced decay, and dry stage. Insect collection during decomposition was done using a sweep net, and the insects were preserved in alcohol for identification. Carrion insect families identified included Calliphoridae, Muscidae, and Dermestidae, with Calliphoridae being the most abundant and the first to colonize the decomposing carrion.
The findings from this study underscored the forensic importance of carrion insects, emphasizing their potential use in forensic investigations to estimate post-mortem intervals, causes of death, and places of death. Given the biological similarity between pigs and humans, these findings could contribute to solving human crime cases.
Table of Contents
1. INTRODUCTION
1.1. Forensic Entomology
1.2. Forensic Entomotoxicology
1.3. Carrion Insects
1.4. Sniper
1.5. Aims and Objectives of the Study
2. LITERATURE REVIEW
2. Forensic Entomology
2.1. Areas of Forensic Entomology
2.1.1. Urban forensic entomology:
2.1.2. Stored-product forensic entomology
2.1.3. Medico legal forensic entomology:
2.2. Decomposition
2.2.1 Fresh stage
2.2.2 Bloat stage
2.2.3 Active decay stage
2.2.4 Advanced decay stage
2.2.5 Dry remains stage
2.3. Succession of Carrion Insects
2.4. Arthropods associated with Carrion
2.4.1 Calliphoridae
2.4.2 Muscidae
2.4.3 Sarcophagidae
2.4.4 Dermestidae
2.4.5 Cleridae
2.4.6 Silphidae
2.5. Animal Euthanasia
2.6. Forensic Entomotoxicology
2.6.1 Review of Previous Studies
2.7. Sniper (Dichlorvos)
2.8. Detection of Toxins in Carrion Feeding Insects
2.9. Justification of study
3. MATERIALS AND METHODS
3.1. STUDY SITE
3.2. SAMPLE COLLECTION AND PROCESSING
3.2.1. Sampling for insects
3.2.2. Sampling for maggot
3.2.3. Sampling for pupa
3.2.4. Measurement of environmental variables
3.3. SAMPLE ANALYSES
4. RESULTS
4.1. Abundance and species composition of carrion insects on pig carcass
4.2. Carrion Insect Succession on Pig carrion
4.3. Effect of sniper insecticide on the length and weight of larva
4.4. Variations in environmental variables at the field site
5. DISCUSSION
5.1. Abundance and species composition of carrion insects on pig carcass
5.2. Carrion insect succession on pig carcass
5.3. Effect of Sniper insecticide on the length and weight of larva
5.4. Variations in environmental variables at the field site
5.5. Conclusion
Research Objectives and Themes
The primary objective of this study is to evaluate the effects of the organophosphate insecticide "Sniper" (Dichlorvos) on carrion insect development and succession patterns by using pig carcasses as human surrogate models. The research investigates how this specific poison, often associated with suicides and homicides, influences the colonisation, diversity, and developmental metrics of necrophagous insects, ultimately aiming to improve the accuracy of post-mortem interval estimations in forensic investigations involving poisoned bodies.
- Comparison of carrion insect abundance and diversity between poisoned and control subjects.
- Examination of the effects of Sniper insecticide on larval growth rates (length and weight).
- Assessment of insect succession patterns across five stages of decomposition.
- Correlation of environmental factors (temperature and humidity) with insect activity and decomposition rates.
Excerpt from the Book
1.2. Forensic Entomotoxicology
Forensic entomotoxicology is the study of the effect of toxins and drugs on the developmental stages of carrion-feeding insects (Goff and Lord, 2001). This is the analysis of toxins in arthropods, which consists of mainly flies and beetles that feed on carrion. This enables investigators to determine whether toxins where present in a body at the time of death.
As these insects feed on carrions, they ingest, incorporate and accumulate the drugs and toxins in the carrion into their own body. These drugs and toxins will then be locked in the cuticle of the larvae or empty pupal cases, therefore, they can be used to analyze for toxins. A drug or toxin can be found in a larva when its rate of absorption is more than its rate of elimination.
The type of drug or toxin found in an insect and their concentration can affect the growth rate of the insect, therefore, it is important to understand the effects of drugs and toxin on their development rate. The post-mortem interval (PMI) can be calculated by considering the insect succession during the decomposition and the developmental stage at which the insect was found.
Summary of Chapters
INTRODUCTION: Provides fundamental definitions of forensic entomology, entomotoxicology, and the role of carrion insects in death investigations, while introducing the specific pesticide, Sniper (Dichlorvos).
LITERATURE REVIEW: Details the categorisation of forensic entomology, the stages of vertebrate decomposition, successional patterns of arthropods, and reviews existing studies on toxin detection in carrion insects.
MATERIALS AND METHODS: Describes the experimental design, including the use of domestic pigs, the application of insecticide, and the specific field protocols for sampling insects and environmental variables.
RESULTS: Presents empirical data on insect species composition, succession matrices, and the specific impact of the insecticide on larval developmental stages and environmental variables.
DISCUSSION: Interprets the findings by comparing observed data with existing literature, validating the importance of specific insect families, and assessing the forensic implications of toxin-delayed decomposition.
Keywords
Forensic Entomology, Forensic Entomotoxicology, Sniper insecticide, Dichlorvos, Decomposition, Post-mortem interval, PMI, Carrion insects, Calliphoridae, Sarcophagidae, Muscidae, Dermestidae, Diptera, Coleoptera, Bioaccumulation.
Frequently Asked Questions
What is the core focus of this research?
The work focuses on how the presence of the insecticide "Sniper" (Dichlorvos) in a deceased body—using a pig as a surrogate—alters the normal succession and developmental process of necrophagous insects.
What are the primary themes addressed?
Key themes include insect succession patterns, larval developmental biology, toxicological impacts on insects, and the forensic application of these findings to estimate the time and circumstances of death.
What is the ultimate goal of the investigation?
The goal is to determine if analysis of insects found on poisoned corpses can reliably serve as forensic evidence to estimate the post-mortem interval and potentially identify poison-related causes of death.
Which scientific methodology was employed?
The study used a comparative field experiment, comparing an insecticide-treated pig carcass to a control carcass, and monitored them through all five stages of decomposition while collecting insect samples.
What is covered in the main section of the document?
The main section covers the literature background on forensic entomotoxicology, detailed field site procedures, observational results of insect colonisation, and an analysis of how poison delays or changes typical decomposition stages.
Which keywords best define this work?
The work is best defined by terms such as forensic entomotoxicology, post-mortem interval (PMI), carrion insects, insect succession, and Dichlorvos toxicity.
How did the poisoning specifically affect larval development?
The study found that larvae on the poisoned pig were generally smaller and lower in weight compared to those in the control group, indicating that the toxin disrupts their growth process.
Does environmental temperature impact the results?
Yes, the document observes that higher ambient temperatures correlate with faster decomposition and increased insect abundance, emphasizing that these environmental factors are critical for accurate forensic modelling.
- Citar trabajo
- Anonym (Autor), 2023, Insecticide and Insects. A Forensic Analysis of Pigs as Human Surrogates in Crime Investigations, Múnich, GRIN Verlag, https://www.grin.com/document/1366205
