Forensic Entomology

Introduction

Forensic entomology has been utilized in various aspects of human medicolegal death investigation since thirteenth-century China. However, the use of entomological evidence in wildlife and animal investigations has not been widely adopted by the forensic science or wildlife conservation communities. Nevertheless, with increased awareness and training for wildlife conservation officers, the use of forensic entomology in the investigation of wildlife crimes is increasing. A recent example of the application of wildlife forensic entomology is from Canada. At the peak of summer in Winnipeg, Manitoba, witnesses discovered three dead black bears near a garbage dump. The animals had been shot, disemboweled with gallbladders removed, and covered in garbage. The removal of the gallbladders suggested a profit motive. Authorities apprehended suspects in the area, but none possessed any animal tissue at the time of the arrest. Officers on scene understood the use insects in death investigations and were able to collect insect eggs from the abdominal wounds. Part of the collected samples were preserved for examination, while the remainder were placed alive on bear liver for observation. The consulting forensic entomologist, Dr. Gail Anderson, identified three species of blowflies (Diptera: Calliphoridae) on the remains: Phormia regina, the black blowfly; Lucilia sericata, the common green bottle fly; and L. illustris, the green bottle fly. These flies are well known in the forensic entomological community, develop at a predictable rate dependent upon ambient temperature, and primarily oviposit on freshly dead animals. Dr. Anderson was able to use this information to estimate the age of the insects when collected from the bear carcasses. Since colonization of the carcasses with fly eggs would likely not have occurred until after the bears had been killed, the estimated time of colonization was used to estimate the animal time of death. This work positively linked the apprehended suspects to the bears and resolved with each poacher serving jail time (Anderson, 1999).

Background

Forensic entomology is the intersection between arthropod science and the judicial system (Amendt et al., 2007; Benecke, 2008; Smith, 1986; Byrd & Castner, 2010). Entomology is the study of arthropods, particularly insects and their close relatives. The word is derived from the Greek entomo, meaning insect, and logus, meaning study. The field involves a range of biological disciplines and applied fields, one of which is forensics (Gullan & Cranston, 2009). The common denominator of these disciplines is that they all involve insects as the focus of study.

All arthropods have several basic characteristics in common: bilateral symmetry, segmented external appendages, an exoskeleton formed from chitin (or long-chain polymer of N-acetylglucosamine, a derivative of glucose), and external segmentation. Arthropods are broken up into several groups based on their external characteristics. One can differentiate insects from all other arthropods based on the presence of three major body regions (head, thorax, and abdomen), a single pair of antennae, often modified for specialized functions, and three pairs of segmented legs (Foottit & Adler, 2009; Gullan & Cranston, 2009).

Insects are the most diverse group of organisms on earth. They constitute approximately half of the global species diversity and represent 50% of all described species of living organisms (Foottit & Adler, 2009). Members of this group are found in all ecosystems and have the ability to exploit vacant niches through adaptation. Their small size, highly organized neuromotor system, and rapid developmental cycles allow these organisms to cope with variable environments (Gullan & Cranston, 2009). It is this coping ability that makes insects such a valuable tool in forensics.

While forensic entomology is any intersection between entomology and the judicial system (Catts & Haskell, 2008; Byrd & Castner, 2010), wildlife forensic entomology is a specific subset

Basic Insect Anatomy of that science (Anderson, 1999). Wildlife forensic entomology is a branch of forensic entomology dealing specifically with animals other than humans. This branch tends to focus on domestic animals, although, as illustrated in the introductory case, has been successfully used in poaching and other cases involving wild animals. It is uniquely simple to use our knowledge of forensic entomology in a case involving wildlife; the bulk of forensic entomological research has been carried out not on human cadavers, but on animal carcasses (Table 5.1). This leads to a large amount of knowledge associating insects with various animals. Often, whatever animal is present in a wildlife forensic entomology case has an associated decomposition and succession study, which leads to a direct application of forensic entomological research to this particular discipline.