Anth 245 1st Edition Lecture 14Outline of Last Lecture- Types of Abuse - Who are abusers - Who are the abused - Long Bone fractures - Take home pointsOutline of Current LectureCurrent Lecture- Insect basics- TSD- Blowfly Life Cycle- Estimating TSD- Insect CollectionForensic Entomology - Entomology - study of insects - Forensic entomology - study of insects applied to medicolegal issues - Training - MS or PHD in entomology - Board certified - Typcially empoyeed by a university - Numerous and Diverse - 700,000-900,000 known insect species - more than 3 times than all other species combined - there are 5,500 species of mammals - Highly specialized - Live in most environments - Present 250 million years ago Insect basic - Invertebrates - Cold-blooded - Exoskeleton - 3 body regions- Head - Thorax - Abdomen - 3 pairs of legs (most have 2 sets of wings) Insect Growth - Exoskeleton hampers growth - Overcome through metamorphosis - Egg - nymph - adult (non-flies) - Body generally similar, just shed skin and grow bigger (e.g. grasshopper) - Egg - larva - pupa - adult (flies) - Body change with each stage (e.g. butterfly - caterpillar) - Look very different at each stage Death Investigations - want to answer: who, what, when, where, why, and how? - Forensic entomology focuses investigation on when - Rigor, liver, and algor mortis can be great indicators but not always - Only Initial 72 hour window - As the post mortem interval increases, the predictive accuracy decreases Time Since Death (TSD) - Post mortem interval - Necrophagous insects - Carrion eaters - Insects are the primary carrion processors - Detect Carrion in minutes - Highly specialized - Tight coverings, deep burial will delay infestation - If body is accessible, they will find it - Eat 90% of carcass; all parts but skeleton - Two main insect orders: Diptera (flies) and coleoptera (beetles) - Necrophagous Insect Succession - Flies - Blow flies, flesh flies - Early arrivers - Decaying flesh is food source - Common - Beetles - Come later- weeks after death - Dried flesh and larval flies are food source- Feed along underside of body - Other - Wasps, ants, feed off carcass and fly/maggot mass - Represent growing ecosystem - Use types of insects present and knowledge of insect succession to determine TSD Blow Fly Life Cycle - Eggs - Laid in open, moist orifices (mouth, eyes, ears, nose) and wounds within minutes of death 2-3 mm long - Hatch after 1-2 days (depends on species type Larvae - Maggots - Three Stages (1st, 2nd, 3rd instars) - Two molts separate stages - Feed at carcass as group (maggot mass) from egg site - Post-feeding larvae: last period of 3rd instar - 12mm long - 8-12 days into life cycle - Migrate away from carcass Pupae - 9mm long - 18-24 days into life cycle - Living pupa inside of a pupa case - Adult fly emerges from case - Empty cases stay for years Adult - Emerge 20 or more days after egg - Mate - Females lay100 eggs each - Live from 1-3 weeks - Feed from Carcass Blow fly life cycle has 6 parts: egg, 3 larval stages, pupa, adult Estimating TSD - Evaluate Oldest stage of blow fly present - Determine species and rate of development- Determine temp. of scene - Insects are cold blooded so development is directly related to temperature (higher temp = quicker development) - Critical in any TSD estimation - Accumulated degree days - av. temp for each day - Rates of development for species of blow flies and flesh flies based on temp. known - When was egg laid? - Known species - Rate of development - Temp info Insect collection - Collect live and preserve eggs and larvae for analysis - Collect 100-200 larvae focus on largest - Collect live pupae and empty pupal casing - Collect live adults if they have first emerged - Also collect other insects (beetles) - Collection done with aerial nets, tweezers, brushes - Specimens placed in vials of preservative or rearing chambers Collection of Other Evidence - Temperature Collection - At scene, air, ground, body, soil, maggot mass - Temp. info from nearby weather station - Soil collection - Photograph and Video the scene Limitation in Estimating TSD - Outside scenes primarily (though can be inside in some cases) - Depends of season - Need to know temperature info - Need to know other variables (e.g. if body was wrapped, if body was buried) - Need to have accurate collection - Often only can give a minimum TSD WHERE - can sometimes determine if body was moved - Some species are geography/location sensitive - Pupae cases remain for years and shown to be at body location HOW- Eggs found in openings and wounds - Colonization patterns - Drugs and Poisons - Maggots and beetles can be tested for alcohol, drugs, and toxins - Child/elderly person