Entomology Chapter 12

Entomology Study of insects and arthropods Invasion in foods consumed by humans Improper use of pesticides Determine postmortem interval (PMI) of corpse Time of death

Determining Time of Death (PMI) Determined by presence of species of insects and arthropods Blowflies arrive quickly and first Lay eggs near moist areas of the body (eyes, mouth, nose, open wounds) Larva (maggots) go through three different stages of growth (instars) on the body First instar occurs 8 hours after egg is laid Second instar occurs 20 hours later Third instar occurs 20 hours later After 5 days, larva stops feeding and rests After a few more days, larva become pupa After 3 weeks since the egg was laid, adult flies emerge

Other Factors affecting PMI estimates Weather Body enclosed or wrapped Presence of drug or poisons

Body Decomposition and Arthropods Necrophages Insects that feed on the corpse tissue Flies Omnivores Feed on body and other insects on corpse Wasps and beetles Predators & Parasites Feed on insects on corpse Incidentals Insects that use the body as their normal habitat (make it their home) Spiders, centipedes, mites

Stages of Decomposition Fresh 1-2 days Adult blowflies, fresh flies and yellowjackets Bloated 2 - 6 days Blowflies, flies, beetles, yellowjackets Decay 5 – 11 days Flies, beetles, cockroaches Postdecay 10 – 24 days Fruit flies, gnats, beetles, flies Dry stage 24+ days Ants, flies, beetles

Blow Fly Metamorphosis Blow flies are attracted to dead bodies and often arrive within minutes of the death of an animal. They have a complete life cycle that consists of egg, larva, pupa, and adult stages. 1st – Adult flies lay eggs on the carcass especially at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc. 2nd – Eggs hatch into larva (maggots) in 12-24 hours. 3rd– Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instar stages. 1st Instar - 5 mm long after 1.8 days 2nd Instar - 10 mm long after 2.5 days 3rd Instar – 14-16 mm long after 4-5 days 4th – The larvae (17 mm) develop into pupa after burrowing in surrounding soil. 5th – Adult flies emerge from pupa cases after 6-8 days. Adult Pupa Eggs 3rd Instar Larva 1st Instar Larva 2nd Instar Larva It takes approximately 14-16 days from egg to adult depending on the temperatures and humidity levels at the location of the body. Image: http://www.umext.maine.edu/images/FlyLife.jpg Information: http://www.kathyreichs.com/entomology.htm and http://www.forensicentomologist.org/

Entomologist Evidence Collection Collect insects on and around body Help determine sight of trauma Help determine cause of death Can use insects and perform toxicology