Forensic Entomology

Forensic entomology is the use of insects in the investigation of crime scenes and criminal investigations. They play a very important role in determining vital information such as the time of death and the cause of death of an individual. Detection of drug use, wounds and whether a body has been moved or not can all be confirmed by insects, but can also be assisted by other factors that come into play. The most significant insects that are studied and used in forensic entomology are blowflies. From the day they lay their eggs to their last day as an adult fly they can give key insights to a deceased person's situation and circumstances even if they are not clearly apparent. On occasion, the term 'forensic entomology' is expanded to include

other arthropods, mites, spiders and macro-invertebrates (Gennard, 2012, p. 1). Although there are many ways in which insects can help in criminal investigations, detection of wounds and indication of time of death are the two areas that are going to be further discussed in this essay.
Detection of wounds
When adult blowflies come across a deceased individual, they tend to lay eggs in the natural orifices of the body, where it is warm and moist enough for the eggs to grow and hatch.

However, if a significantly large group of blowflies are found on the body anywhere other than these natural orifices e.g. the mouth and nose, then this can be an indication of a wound or injury on the body. Wounds can be equally as warm and moist as the natural orifices and so blowflies tend to lay their eggs in them, as well as using them as a food source. This will make the numbers increase which in turn draws attention to the injuries and forensic scientists can notice this and investigate them

further.
There are two types of wound that can be found on a deceased individual: perimortem and postmortem. Perimortem wounds are found before the death of a body, and these are the wounds that insects are found at in greater numbers compared to the natural orifices in the body because they bleed a lot more. Postmortem wounds are found when the body is already deceased. These type of wounds are not normally heavily covered in flies because there is a lack of blood flow so they don't bleed as much and are not as warm.
Indication of time of death
One of the most notorious ways blowflies aid in legal investigations is indicating the time of death of an individual. Their life cycle can assist forensic entomologists in estimating when a body became deceased. According to Gennard (2012) the point at which the blowfly lays its eggs when it first comes into contact with the body is considered to coincide with the point of death and its end is considered to be the discovery of the body. There are other physical ways to tell roughly how long a body has been deceased for e.g. the temperature of it, but after about 72 hours there is not much indication from the body alone as to how long it has been deceased for. This is why blowflies are so essential in determining when an individual passed away. To estimate the Post Mortem Interval (PMI) - the time that has passed since a person has died - a sample of the collected insects are killed and preserved prior to being used to estimate the entomological-based portion of the PMI, while others of the same sample or similar sample may be reared to the adult stage for identification (Byrd et al. 2009, p. 372).
Factors such as temperature, time of day and burial of the body however can affect the growth of the blowflies and therefore will be less reliable to use to determine the PMI.

The ideal temperature for the maggots to survive their entire life cycle has been found to be in between 15-25 degrees (Fraser, 2015). Any hotter or colder and the maggots cannot survive long enough to grow into adult blowflies. However, if the temperature was colder, the maggots can go into hibernation and form in groups to keep warm. This doesn't allow them to live their full cycle, but it does enable them to live longer than if they were in a hotter climate, although Gennard (2012) found that the highest temperature for insect growth is in the region of 52.7 degrees. Horsewell (2004) observed that although commonly flies are most active during the day, Green (1951) and Greenberg (1990b) have shown in studies that some species of fly are capable of nocturnal oviposition in certain circumstances. Temperature can also come into effect in this.

If a deceased body is buried deep underground or is encased in tight wrappings, it is harder for the insects to get to the body. If a body is kept in this way, then it may not decompose in the natural order it normally would if it was exposed to the air and to insects. Although, there are some exceptions such as some blowfly larvae, some flesh fly larvae and coffin flies, as these can bury down under wrappings or deep ground and therefore reach the

body.
Therefore evidently, forensic entomology is essential in identifying not only the cause of death of an individual, but also the time of death, along with many key factors that can help aid legal investigations. Wound detection and indication of time of death are just two areas that have been discussed out of many ways that insects can be used in recording information about a deceased body depending on how they are studied and used by entomologists. Information that is not obvious to the naked eye can be identified by insects and used as critical evidence in court cases.