Forensic Entomology Blue blow fly Green bottle fly

Forensic Entomology Blue blow fly Green bottle fly Maggot (larva)

Importance of Flies in Nature • Niche in an ecosystem? – Decomposers – Break down dead organisms to nutrients to be reabsorbed by plants – Use dead organic matter as food source – What would the world be like without decomposers?

Life Cycle of Fly • Egg larvae (3 stages) pupa adult

• Larvae have three stages with molting prior to next stage – 1 st instar – 2 nd instar – 3 rd instar • Pupa – Mature 3 rd instar migrate away from body to pupate (up to 100 yds away) • Time from one stage of life cycle to another varies with species and temperature – Black flies: 14 -15 days at 800 – Bottle flies: 35 days at 800

• Flies are drawn to openings especially wounds because moist and warm • Drawn to smell of blood within 15 -30 sec. – Won’t lay eggs on body that is too old – Green blow flies are first – Black blow flies are second but take longer to move through life cycle – Flesh flies appear but lay newly hatched maggots rather than eggs – 3 rd instar larvae are ravenous and can skeletonize a 50 lb. pig in 36 -90 hrs.

Patterns • Behavior: – Don’t lay eggs after sunset – Some delay laying eggs for 12 -24 hrs after coming to body – Eggs/larvae begin feeding in head region first (open orifices) then the anal/genital region – Eggs/larvae found in other areas is indication of wound • Weather: affects growth and development – Air temp. important – Base temp. is lowest limit below which flies will not grow – Quantify the temp. to look at time for development from one stage to another • Degree hours (DH) = hourly temp – base temp • Accumulated degree hours (ADH) = DH 1 + DH 2 +…. . DHN

• Various drugs can affect the life cycle of insects – Developmental rate changes – Ingest drug along with the tissues – i. e. cocaine speeds up development while arsenic slows it down.

Tests • Use Accumulated Degree Days (ADD) which is a measure of energy needed for growth and development. • Degree Days is energy unit for a 24 hour period • Calculated same as for DH and ADH – Base temp is 10 degrees C for warm weather flies and 6 degrees C for cool weather flies • Collection of samples – Collect air temp – Collect adult flies and maggots (living and dead) from various areas of body – Look for pupa – ID stage and species of each specimen (dead) – Allow live specimens to complete development to ensure species types.

Body Decomposition • “Fresh” stage – moment of death and lasts till body bloats – Body looks normal – First flies appear – Wasps and beetles may arrive to feed on maggots • “Bloated” stage – body visibly inflated – Production of gases from bacteria – House flies appear and help liquefy tissues

• “decay” stage – begins when skin breaks and gases escape – Smelly stage – By end, maggots end of development and leave body to pupate – Corpse has no more flesh only cartilage, bone, skin – No more flies only beetles that feed on what is left

Uses • • Time of death Determine origin of death if body moved Determine origin of drugs Maggots used therapeutically – Cleans out dead tissue – Secrete antibiotics and cytokines which promote new cell growth