Forensic Entomology

• Forensic Entomology


  The study of insects in relation to legal investigations
• Forensic Entomology


  • Insects recovered from a body can provide useful information, such as DNA profiles and indications of trauma
  • Insects can also be used as evidence of abuse or neglect
  • The most common use of insect evidence is to estimate the time since death/ Postmortem Interval (PMI)
  • Insects have specific habitat preferences that can help link a body to a particular location
  • The presence of insects can also indicate the presence of a food source at a crime scene
• Insect Classification


  • Kingdom = Animalia
  • Phylum = Arthropoda
  • Class = Insecta
  • Order = Beetles (Coleoptera), Flies (Diptera)
  • Family = Ground Beetles (Carrabidae), Blowflies (Calliphoridae)
  • Genus = Calliphora
  • Species = Calliphora vimitoria
• Most forensically important insect orders

  • Diptera – Families: Calliphoridae (blowflies) and Sarchophagidae (flesh flies)
  • Coleoptera – Families: Dermestidae (skin beetles) and Cleridae (bone beetles), Staphylinidae (rove beetles), Trogidae (hide beetles)
• Fly


  • Thoracic appendages - 3 pairs of legs, 1 pair membranous wings, 1 pair club-shaped halteres
  • Mouthparts - Adapted for sucking
  • Antennae - Often short with few segments
• Beetle


  • Forewings modified to form hard, leathery coverings (elytra), hindwings membranous and fold under elytra when not flying
• Insect Life Cycles


  • Exopterygotes = adults and larvae look similar (incomplete metamorphosis)
  • Endopterygotes = adults and larvae look very different (complete metamorphosis)
• Life Cycle of the Fly

  1. Oviposition (Egg laying)

  2. Eggs hatch into larvae

  3. 3rd instar larvae often move away from the food source to find a pupation site (post-feeding or pre-pupa)

  4. Adult (imago) flies emerge or eclose from the pupae
• Larval stages in blowfly life cycle


  • Number of slits in the posterior spiracles can be used to identify instar
• Life Cycle of the Beetle

  Beetles typically have 5-10 larval molts
• Urban Entomology


  Insects as pests/nuisances in the human environment
• Urban Entomology


  • Cockroaches
  • Pharos's ants
• Stored Product Entomology


  • Food contamination
  • Spoilage of stored commodity/grains
  • Importation issues - identification country of origin, biosecurity
• Medico-legal Entomology


  • Also known as Medico-criminal / forensic-medical
  • Solving crimes (particularly involving corpses)
• Why use insects for medico-legal purposes?

  • A corpse is a large food resource for flesh-eating insects
  • Many insects are specialist carrion feeders and will quickly colonise (particularly blowflies)
  • Insects occur in large numbers almost everywhere
  • Insect development is fairly simple and predictable
  • The interaction between environmental conditions and insects are well known and predictable
• Insects recovered after a body has been removed


  May still provide useful information
• Presence of insects


  Evidence that a food source (body) was present at the scene
• Full human DNA profiles have been generated from gut contents of maggots feeding on corpses and puparia
• Different habitat preferences


  Could help with linking a body to a particular location
• Habitat preferences


  • Lucilia illustris – Southern England, open woodland and meadows
  • Lucilia caesar – Northern England, forests and shaded habitats
  • Calliphora vicina – urban locations
  • Calliphora vomitoria – rural locations
  • Musca domestica – rarely found far from human habitation
• Preferred oviposition sites include, mouth, eyes, nostrils and genitals
• Location of maggot masses in areas other than preferred oviposition sites


  May indicate a site of trauma
• Presence of insects


  Can be used as evidence of abuse or neglect (wound infestation in living animals (myiasis))
• Estimating PMI


  The most common use of insect evidence is to provide estimates of post-mortem interval
• During hours-days post mortem other indicators give good estimates of time since death (body temperature, rigor mortis, algor mortis, vitreous humour)
• If time since death is longer (weeks – months) insect evidence may be useful
• Estimating PMI


  • Understanding the life cycle allows us to determine PMI from the oldest stage of insects found on a body
  • Predictable stages of decomposition
  • Predictable life stages of insect development
  • Predictable succession of insect groups
  • Temperature dependent development
• Stages of Decomposition


  • Bloat
  • Active Decay
  • Dry Decay
  • Skeletonisation
• Blowflies


  • Volatile organic compounds (VOCs) e.g. sodium sulphide are very effective attractants to blowflies
  • The Calliphoridae have highly developed senses
  • Short antennae with feather-like arista and large surface area
  • Can sense substances given off by decay at very low concentrations
  • Greenbottles can sense a carcass from 6.4 km away!
• Calliphoridae (family)


  • Bluebottles and greenbottles
  • 32 species in the UK in 12 genera
  • Family identified by wing venation and hair patterns on thorax
  • 5 necrophagous genera: Calliphora, Lucilia, Phormia, Protophormia, Cynomya
• What do Forensic Entomologists need to know about insects?

  • Identification and Classification - Species names and their relationships, How to identify insects (using dichotomous keys)
  • Developmental biology - Life cycle history, Timing of life cycle, and stages of the life cycle, Factors affecting life cycle – temperature, humidity
  • Behaviour - Why do they do certain things, What things affect their behaviour
  • Ecology - Geographic distribution/ habitat preference, Relationships with environment, Relationships with other species
• Insects are attracted to dead bodies due to odors produced by decomposition.
• Insects are used as indicators of environmental conditions, such as temperature and humidity.
• Forensic entomologists use knowledge about insect development to estimate the postmortem interval (PMI).
• The third stage is active decay, where the body begins to break down and liquefy.
• The presence or absence of certain species can indicate the time since death.
• The presence of maggots can indicate the time since death, as different species develop at varying rates.
• The second stage is known as bloated, characterized by the accumulation of gases within the body.
• Forensic entomology is important because it helps determine time since death based on the development stage of insects found on or near a body.
• The first stage of decomposition is known as fresh, where there is little visible decomposition.