FORENSIC ENTOMOLOGY

1. FORENSIC ENTOMOLOGY

2. FORENSIC ENTOMOLOGY Forensic entomology – The study of insect matter, growth patterns, and succession of arrival at a crime scene to determine the time to death.

3. FORENSIC ENTOMOLOGY Forensic entomology is commonly used to estimate the time of death when the circumstances surrounding the crime are unknown.

4. FORENSIC ENTOMOLOGY After death, necrophagous insects, or insects that feed on dead tissue, are the first to infest the body. The most common and important of these is the metallic greenbottle or bluebottle flies known as blowflies. Flesh flies may also be present at this stage.

5. FORENSIC ENTOMOLOGY Predator insects may arrive and prey on the necrophagous insects while they are in their weak stages. Next, omnivore insects arrive at the body. These insects will feed on the body, on other insects, and on surrounding vegetation. Ants are an example of omnivore insects.

6. FORENSIC ENTOMOLOGY Last is the arrival of indigenous insects, whose presence on or near the body is coincidental as they move about their environment.

7. FORENSIC ENTOMOLOGY The sequence of arrival of these groups is dependent mostly on the body’s natural decomposition process. Various by-products of decomposition attract one group and repel others over time.

8. FORENSIC ENTOMOLOGY After decomposition begins, insects such as blowflies are the first to infest the body. Their eggs are laid in the human remains and ultimately hatch into maggots or fly larvae, which consume human organs and tissues.

9. FORENSIC ENTOMOLOGY Forensic entomology can identify the specific insects present in the body and approximate how long a body has been left exposed by examining the stage of development of the fly larvae.

10. FORENSIC ENTOMOLOGY This kind of determination is best for a timeline of hours to approximately one month. This is because the blowfly goes through the stages of its life cycle at known time intervals.

11. FORENSIC ENTOMOLOGY By determining the oldest stage of fly found on the body, entomologist can approximate the postmortem interval (PMI). Postmortem interval – The length of time that has elapsed since a person has died. If the time is not known, a number of medical or scientific techniques may be used to estimate it.

12. FORENSIC ENTOMOLOGY All too often insect evidence is accidentally destroyed by emergency personnel who fail to realize the importance of this evidence. In some cases, well meaning emergency personnel have shooed away insects and maggots at a scene.

13. FORENSIC ENTOMOLOGY Some emergency personnel have been seen stomping on maggots as they attempt to flee from the activity around the body. Education in the proper collection and preservation procedures is essential.

14. FORENSIC ENTOMOLOGY The time it takes for a fly to move through each stage depends on the species of fly and the temperature conditions. The time required for stage development is affected by environmental influences such as geographical location, climate, and weather conditions.

15. FORENSIC ENTOMOLOGY For example, cold temperatures hinder the development of fly eggs into adult flies. The forensic entomologist must consider these conditions when estimating the PMI.

16. FORENSIC ENTOMOLOGY Knowledge of insects, their life cycles, and their habits make entomological evidence an invaluable tool for an investigation. If resources allow, all entomological, or insect, evidence should be collected by a forensic entomology expert.

17. FORENSIC ENTOMOLOGY When this is not possible, collection should be carried out by an investigator with experience in death investigation. The entire body and area where insect evidence was found must be photographed and documented before collection.

18. FORENSIC ENTOMOLOGY The temperature of the scene and the center of any “masses” of maggots should also be measured. Specimen samples should be taken from each area on the body where they are found.

19. FORENSIC ENTOMOLOGY For all insects and stages, half of the specimens should be sealed in a glass vial with a food source so that the entomologist can observe their further development.

20. FORENSIC ENTOMOLOGY The other half of the specimens, except for the newly emerged adult blowflies, should be preserved in a sealed glass vial with alcohol for further testing. The newly adult flies should instead be dried out for preservation.

21. FLY: LIFE CYCLE STAGES Eggs 1.The eggs are white and sausage-shaped and are usually laid in clumps. 2. Present in clumps of up to 300 3. Laying to hatching takes 1 day.

22. FLY: LIFE CYCLE STAGES Eggs On fresh corpses, look for these clumps in the mouth, in nasal openings, in the ears, and generally in any area where mucus membranes come into contact with outside air.

23. FLY: LIFE CYCLES STAGES Eggs Also look for them on wounds and bruises. Don’t think that because they haven’t hatched yet they are not important. Eggs can be both identified and aged. Put some of the eggs into alcohol and save some for rearing.

24. FLY: LIFE CYCLE STAGES Larva Larvae or maggots hatch from the eggs. They too are white but are shaped more like a cone that a sausage. The mouth is at the pointed end of the cone, and the maggots uses a pair of “hooks” there to attach itself to the corpse while it feeds.

25. FLY: LIFE CYCLE STAGES Larva Maggots also use the hooks to help themselves move. Normally they move be extensions and contractions of their segmented, legless body. Maggots shed their skin three times. Each time they get a new, slightly larger and slightly different set of spiracles and mouth hooks.

26. FLY: LIFE CYCLE STAGES Larva Differences in the fine structure of the mouth hooks and spiracles can help tell a forensic entomologist both the species the maggot belongs to and how many times it has shed it skin.

27. FLY: LIFE CYCLE STAGES Larva – 1st instar Initially feeds on fluid exuded from the body Migrates into body Hatching to first molt takes 1 day

28. FLY: LIFE CYCLE STAGES Larva – 2nd instar Moves around in maggot mass First molt to second molt takes 1 day

29. FLY: LIFE CYCLE STAGES Larva – 3rd instar Still moves in mass Greatly increases in size Second molt to pre-pupa takes 2 days

30. FLY: LIFE CYCLE STAGES Pre-pupa Migrates away from the corpse seeking a suitable pupation site Does not feed Transforms into pupa Pre-pupa to pupa takes 4 days

31. FLY: LIFE CYCLE STAGES Pupa Resides within puparium Undergoes transformation from larval body form adult fly Does not feed Pupa to emergence take 10 days

32. FLY: LIFE CYCLE STAGES Adult fly Mates on emergence from pupa Feeds on protein from body fluids Lays eggs on corpse Emergence to egg laying takes 2 days

33. FLY: LIFE CYCLE STAGES The eggs hatch and move into the body, often within 24 hours. The life cycle of a fly from egg to maggot to fly takes from two to three weeks. It can take considerably longer at low temperatures.