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Abstract If you're looking for an experiment that will gross out just about everyone, you probably can't do much better than this! This project investigates an important question in the field of forensic entomology. Just make sure to get permission at home before you start.Objective The goal of this project is to determine if maggot mass temperature increases as the number of maggots in the mass is increased. Introduction This project is not for those that are easily grossed out. If this is you, just hit the back button on your browser before reading further, and you'll be fine. If you aren't squeamish, and you think you might be interested in doing a project related to forensic entomology, then keep on reading. "Forensic entomology is the study of insects and other arthropods in a legal context. The applications are wide-ranging, but the most frequent is to determine the minimum time since death (minimum post-mortem interval, or PMI) in suspicious death investigations. This is done by identifying the age of the insects present on a human corpse, which can provide a relatively precise estimate in circumstances where pathologists may only be able to give a broad approximation. The fundamental assumption is that the body has not been dead for longer than it took the insects to arrive at the corpse and develop. Thus, the age of the oldest insects on the body determines the minimum PMI." (Hall and Brandt, 2006) All insects start out life as eggs, although some hatch within the body of the mother, who then seeks out a source of food on which to deposit the living larvae (fly larvae are also called maggots). The flesh flies (scientific name Sarcophaga bullata) you will use in this project are an example of this type of insect. Blow flies (family Calliphoridae) are the usual "pioneer" species on an exposed animal corpse. Flesh flies generally arrive a day later. However, since flesh flies are deposited as larvae, and blow fly eggs take about 24 hours to hatch, the flesh fly maggots can develop as quickly as the blow fly maggots (Major, 2003). As young insects grow and develop, their bodies change in a process called metamorphosis. In a few species, for example silverfish, only size changes. In other species, there is a simple change—development of wings in grasshoppers, for example. In other insect species, such as flies, there is a complete metamorphosis from the larval stage to the adult body form. (Borror and White, 1970; Illinois DNR, 2003)
Insect larvae pass through multiple stages of growth, called instars. Because insects must shed their exoskeleton in order to grow, each growth stage is separated by a molt (also called ecdysis). As shown in Figure 1 (above), fly larvae pass through three instar stages (two molts). At the end of the third instar stage, the maggots disperse, seeking a location in soil before pupation. Pupae are inactive, and do not feed. Adults emerge from the puparium in one to two weeks at room temperature (Figure 2, below). Pupae can hibernate for long periods during colder temperatures, allowing flies to overwinter in the pupal stage and to emerge as adults in warmer spring weather.
Development of fly larvae can be strongly dependent on temperature. Figure 3 (below) shows the total development time for blue bottle blow flies, from egg-laying to emergence of adults (in days), as a function of ambient temperature (in °C). You can see that over the range from 10 to about 17°C, each 1°C increase in temperature results in a significant decrease in development time.
Flies lay eggs and larvae in clumps, and the developing maggots mass together as they grow. The individuals benefit from shared secretions which aid in digestion and produce an alkaline environment conducive to larval growth. "The larval infestations might look gruesome, but they are a vital component of the natural recycling of organic matter and, on human bodies, they can provide vital clues to the timing and cause of death." (Hall and Brandt, 2006) The mass of maggots can also cause a local increase in temperature. The goal of this project is to determine whether maggot mass temperature increases as the number of maggots in the mass increases. A more advanced project (see the Variations section, below) would also try to determine if increasing maggot mass can lead to decrease in development time, and, if so, over what temperature range. Terms, Concepts, and Questions to Start Background Research To do this project, you should do research that enables you to understand the following terms and concepts:
Questions
Bibliography
Materials and Equipment To do this experiment you will need the following materials and equipment:
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Forensic Science Technician Guilty or not guilty? The fate of the accused in court lies with the evidence gathered at the crime scene. The job of the forensic science technician is to gather evidence and use scientific principles and techniques to make sense of it. It can be a grueling and graphic job, but very rewarding. If you like the idea of using science to help deliver justice, then you should investigate this career. |
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Biologist Life is all around you in beauty, abundance, and complexity. Biologists are the scientists who study life in all its forms and try to understand fundamental life processes, and how life relates to its environment. They answer basic questions, like how do fireflies create light? Why do grunion fish lay their eggs based on the moon and tides? What genes control deafness? Why don't cancer cells die? How do plants respond to ultraviolet light? Beyond basic research, biologists might also apply their research and create new biotechnology. There are endless discoveries waiting to be found in the field of biology! | |
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