Forensic Entomology


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Publications



The 4 page brochure above (title page shown) gives descriptive details on how to collect entomological evidence and depicts the flies and beetles (back page) that are common in corpse succession in Western Australia. Both the poster and brochure are available for $AUD10.00. The poster can be printed with the text and pictures substituted with flies and beetles found in a particular region. Costs can be negotiated by contacting the forensic entomologists/authors (below).

The poster above depicts the material required by an entomologist from a corpse or a fly struck wound to estimate either a post-mortem or post-injury time interval. It is an extension of the diagram created by the late E. Paul Catts in Entomology and Death: A Procedural Guide. The poster is available in three sizes from the forensic entomologists/authors (below).
 


The Entomology Kit pictured above is for use by police services and pathologists when a Forensic Entomologist is unable to attend a scene of crime. The kit comes complete with fold-up insect net, ventilated containers  for insects and soil containing insects, plastic all-purpose forceps, 70% alcohol and instructions in the form of the poster and brochure above. A new inclusion is a data logger weather station.


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Collecting From a Corpse
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Fly Egg Masses
 
Blowflies usually select natural body openings for oviposition (eyes, nostrils, ears, mouth, and less so at anus and genitals) but will preferentially lay eggs on any wounds that may be present. Frequently eggs are laid underneath the body. Eggs are typically laid in rafts.

COLLECTION: Egg rafts should be collected, with some placed in ethyl alcohol (70% ethanol) and others into a well-ventilated container and refrigerated. Eggs will later be placed onto a food media and allowed to proceed to eclosion.

Fly Larvae
 


Blowflies detect carcasses within a few hours after death. Flies arriving on a carcass are typically divided into primary, secondary and tertiary phases. Flies arriving early (primary species) and ovipositing on a carcass (e.g. Calliphora and Lucilia spp) clearly have a competitive advantage, whereas later arrivals (secondary species) such as Chrysomya, Sarcophaga and a few Calliphora species (Calliphora dubia) compensate for this by (1) dumping live larvae (i.e., viviparity or larviposition) and by (2) predating on other larvae.

COLLECTION: The hairy maggots of Chrysomya are heavily predacious on both other fly species and their own (carnivorous) at high densities. This is important to remember when collecting both hairy maggots (Chrysomya spp) and smooth maggots (Calliphora and Lucilia spp) from the same corpse - if they are placed together in a vial, the smooth maggots will soon be consumed by the hairy maggots, and will not be represented in the entomological evidence gathered. Collect all size maggots (1st, 2nd and 3rd instars) and preserve half in ethyl alcohol, and keep the rest alive in ventilated container and refrigerated (4-5 C; record time of refrigeration). The distribution of maggots on a body may sometimes give a clue to the cause of death. Any departure from this pattern, such as the presence of maggots in the chest and their absence from the body openings, would suggest that a wound had been inflicted on the chest, with blood attracting flies to that site first, even though the wound is no longer visible. Keep an accurate record of the site of collection (head wound 2 cm above left eye, for example).

Fly Pupae




The largest larval stage (usually the 3rd instar) pupates, forming a dark brown casing, which is often in the soil directly under or adjacent to their food source. Larvae often "wander" (between 3 and 10 m) from a carcass to avoid competition and seek dry soil for pupation.

COLLECTION: Some of these pupae need to be collected and placed in a ventilated container and some into ethyl alcohol. Within the pupa, the fly larvae changes form into an adult fly, which later breaks free from the pupal shell leaving an empty pupal case behind, which is evidence of previous fly emergence. Empty pupal cases (adults have already emerged) also need to be collected and placed into a container.

Beetles and Their Larvae


Hister Beetle
(Histeridae)

Roves Beetles - Devils Coachmen
(Staphylinidae)

Carcass Beetles
(Trogidae)

Hide Beetles
(Dermestidae)
Beetle larvae are also helpful when determining post-mortem time interval. Beetle larvae often reside in fly breeding resources, and they can be distinguished from fly larvae by the following: Beetle larvae possess a hard, head capsule, often brown in colour. Fly larvae lack a head capsule, instead having distinct, internal, black mouth hooks (cephalopharyngeal skeleton of mouthparts) at the anterior end of their body. Beetle larvae have six legs on their body immediately behind the head. Fly larvae lack legs. To the left are some coleopteran insects commonly associated with corpses in Western Australia.

COLLECTION: Collect beetle larvae the same way as for fly larvae described above. Adult beetles can be collected from or around the corpse or with a sweepnet and preserved in ethyl alcohol.


Adult Flies


Australian sheep blowfly
(Lucilia cuprina)

Green blowfly
(Lucilia sericata)

Bluebodied blowfly
(Calliphora dubia)

Western goldenhaired blowfly
(Calliphora albifrontalis)

Western Australian brown blowfly
(Calliphora varifrons)

Hairy maggot blowfly
(Chrysomya rufifacies)

Steelblue blowfly
(Chrysomya saffronea)

Small hairy maggot blowfly
(Chrysomya varipes)

Oriental latrine fly
(Chrysomya megacephala)

Black carrion fly
(Hydrotaea rostrata)

Cheeseskipper
(Piophila casei)

Housefly
(Musca domestica)

Fleshfly
(Sarcophagidae)
The collection of live stages of larvae and pupae are vital for the determination of species. Although larvae can be identified, adult flies are much easier to classify. To the left are some dipterous insects commonly associated with corpses in Western Australia.

COLLECTION: Collect adult flies with sweepnet around corpse and preserve in ethyl alcohol.

 

Other insects such as wasps and ants that are present on the corpse should also be collected.


 

Supportive Information

Forensic Entomologists also require supportive information to determine the time of death, or Post-Mortem Interval (PMI) such as:
1. Who is the officer in charge and medical pathologist (phone, fax number)?
2. General description of death scene
a.  Vegetation (type, height)
b.  Slope and exposure to sun and/or artificial light
c.  Sun/shade ratio
d.  Indoors/outdoors (windows open/closed)
e.  Concealment of body (car boot, bins etc)
3. Notations of insect activity.
4. Collect insects around corpse (adult flies, fly larvae and beetles).
5. Collect insects on corpse when permitted (adult flies, fly larvae and beetles).
6. Collect insects beneath corpse after its removal (fly larvae/pupae and beetles).
7. Collect substrate/soil samples (sieve soil to collect fly larvae and/or pupae).
8. Arrange to record meteorological data at the scene over the next 7 days (min/max temperatures and relative humidity).

 

Internet Links

Forensic Image Processing
Forensic Entomology Web Ring;

 

 

Authors: Dr Ian Dadour and Dr David Cook.