Improving forensic investigations: Student and Blow fly behavior

Forensic entomology is the use of insects in legal investigations and is most commonly applied in legal matters for death investigations. Forensic entomologists are contacted to assist law enforcement in estimating a minimum postmortem interval. A postmortem interval is the amount of time between death and discovery of remains. Forensic entomologists can aid law enforcement by providing a time of colonization, which is when insects first arrive to remains and deposit eggs soon after arrival. Blow flies (Diptera: Calliphoridae) are particularly useful for this purpose because they are commonly recognized as primary colonizers as they can arrive within minutes after death. If blow flies readily have access to remains, then the time of colonization estimate provided by the forensic entomologist will be indicative of the minimum postmortem interval. This estimate can provide a timeframe of death for an individual when lacking other indicators or corroborate law enforcement timelines. Proper training and education for law enforcement or forensic technicians on collecting insects as evidence is imperative for using insects to determine minimum postmortem intervals. Additionally, research on forensically relevant insects to better understand their behaviors will strengthen these estimates.

Forensic science is embedded into American culture through media such as television, movies, and more recently, podcasts and social media. It is likely that students enrolled in forensic science programs have had previous exposure to these topics and may have preconceived ideas of the field and protocols. However, forensic entomology is an area that is often overlooked or under-utilized, both by law enforcement and the media. Forensically relevant insects (flies, beetles, maggots) are typically perceived as disgusting, creepy, or bizarre, but individuals in forensic science job positions will likely encounter them in their career. Most students have not learned from forensic examples, so it is valuable to bring forensic entomology teaching models in the classroom to gain exposure. I hypothesized that students in forensic science courses will become more comfortable with forensic entomology topics after learning about them in a controlled environment, but students in a course with an experiential learning component in the laboratory will show a greater positive shift in comfort. Students in two courses, one with a lab component and one that is lecture only, were surveyed before and after the course to learn how attitudes on these topics shift. For the course with the laboratory component, there was a significant difference in comfort with forensic entomology topics. There was no significant difference in comfort in the lecture-only course. This research demonstrates the value of bringing forensic entomology models into the classroom and how experiential learning impacts attitudes surrounding an unfamiliar topic.

In a laboratory setting, research on forensically relevant insects, particularly blow flies, is crucial to our understanding of their behaviors and life history traits. It is important to successfully maintain colonies of these insects in the laboratory to learn information that can be applied to death investigations that include insects as evidence. While it is well established that blow flies require sucrose and water to survive and females require protein for ovarian development, there is no consensus on which protein and sugar resources are most optimal. Phormia regina Meigen (Diptera: Calliphoridae) longevity and fecundity while feeding on various diets were examined in order to provide recommendations on which resources are best for P. regina in terms of lifespan and largest number of viable offspring. The protein sources evaluated were blood and milk powder, and the sugar sources were honey and sugar cubes. Additionally, 3 different P. regina populations from Indiana, California, and Colorado, were included in this research. I hypothesized that population and diet influences P regina lifespan and reproductive success. I predicted that all populations would live longer and produce more viable offspring while feeding on blood and honey, and the Indiana population would produce more viable offspring and live longer than the other populations. There was no significant difference in the number of offspring produced on the various diets within the populations, but there were some differences in lifespan. There were significant differences in lifespan and number of offspring between different populations of P. regina. All resources included in this study are suitable for the rearing of blow flies in terms of reproductive success and longevity.

Another consideration for blow flies is the complexity of oviposition and numerous factors that can influence this process. Some of these factors include moisture, substrate size, predation, and competition. Research has demonstrated that oviposition preferences shift with substrate age (amount of exposure time) and tissue type. Blow flies also tend to lay more eggs on aged substrates compared to fresh. This topic has been assessed using pieces of tissue and various types of carcasses, however, there is a lack of research that examines blow fly oviposition behavior on aged pig carcasses in the field and laboratory settings. Field and laboratory experiments were conducted to assess blow fly oviposition behavior on pig carcasses, and the ages included were fresh controls, 24-, 48-, 72-, and 96- hours of exposure with insects excluded. I hypothesized that the number of eggs laid would increase with age, time to oviposition would decrease with age, flies would lay eggs in places other than natural openings on aged treatments, and initial colonizing species would vary between treatments. The field component of this study looked at initial colonizing species of various aged treatments, time to oviposition, and oviposition site preferences. This revealed differences in initial colonizing species and oviposition sites but no difference in time to oviposition. The laboratory research examined blow fly oviposition site preferences, time to oviposition, and number of eggs laid by two forensically relevant blow fly species, P. regina and Lucilia sericata Meigen. Both species laid more eggs on aged carcasses compared to fresh, and moisture caused flies to lay eggs on the surface in aged treatments rather than natural openings. Research on aged substrates can assist with answering law enforcement questions about insect activity when there is a delay in accessibility to remains.

Through educating students in forensic programs on forensic entomology, students are more likely to leave the program with an informed perspective of what death investigations and protocols entail. Through this experience, they are also able to gain a better sense of their career goals. Researching blow fly diet in the lab provided a better understanding of the factors that have the greatest impact on blow fly fecundity and lifespan. Oviposition behavior research is an important area of study that clarifies blow fly preferences and how they interact with remains. The three overarching topics in this thesis, student learning in forensic entomology, blow fly laboratory diet, and oviposition behavior all work towards strengthening forensic investigations. Better preparing forensic personnel and contributing to knowledge about factors that influence blow fly behaviors improves the application of insects to death investigations.