Forensic entomology insects relevant to PMI and Aquatic entomology

1. Insects of forensic
importance

2. Decomposition
• Stages of Decomposition
1 Fresh Stage (Days 1-2)
• Commences at death, ends when bloating is first evident.
• Breakdown of protein and carbohydrates into simpler compounds
2 Bloated Stage (Day 2-6)
• Putrefaction begins. Gasses produced by anaerobic bacteria
• inflate the abdomen.
3 Decay Stage (Days 5-11)
• Abdominal wall breaks allowing gasses to escape.
• Carcass deflates.

3. 4 Post-decay Stage (Days 10-25)
• In dry habitats, remains are skin, cartilage, and bones.
• In wet habitats, viscous material in the soil under the remains.
5 Dry Stage (Days 25+)
• Mainly bones and hair remain. Odor is primarily that of normal
soil and litter. Can last several months to years.

5. Major Groups of Insects associated with Cadavers
 Flies (Diptera)
Blowflies
Flesh Flies
House Flies
Beetles (Coleoptera)
Carrion Beetles
Dermestids
Rove Beetles

6. Classification
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Calliphoridae
Genus: Chrysomya
Species: C. megacephala
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Suborder: Polyphaga
Infraorder: Staphyliniformia
Superfamily: Staphylinoidea
Family: Silphidae

7. Blue Bottle Flies (Blow flies)
Family name: Calliphoridae
Blowflies often are an
attractive blue-green,
metallic color, leading to the
common English names,
blue-bottles and greenbottles.
•They also come in a
nonmetallic,
brown form, but all
blowflies usually relatively
large flies.

8. Green Bottle Flies (Blow flies)
Family name: Calliphoridae
Blow flies can pick
up faint traces of
the odor of decay
from up to 2.5 km
away and lay their
eggs in a suitable
corpse.
Blow flies are one
of the first insects to
arrive at a cadaver
– they prefer fresh,
moist flesh.

9. Common House Flies
Family name: Muscidae
Adults are most
common at corpses
in the early stages
of decomposition
when the corpse is
moist.
•The larvae are
usually dung
feeders.

10. Flesh Flies
Family name: Sarcophagidae
• Most flesh flies breed in
• dead animals, dung, or
• decaying material, but a
• few species lay their
• eggs in the open
• wounds of mammals;
• hence their common
• name. Most flesh flies breed in
• dead animals, dung, or
• decaying material, but a
• few species lay their
• eggs in the open
• wounds of mammals;
• hence their common
• name.
Most flesh flies breed in
dead animals, dung, or
decaying material, but a
few species lay their
eggs in the open
wounds of mammals;
hence their common
name.

11. Carrion Beetles
Family name: Silphildae
Silphids are large
carrion beetles that
feed on both carrion
and fly larvae.
Even though adults
have been recorded
feeding on carrion,
they cannot survive on
it alone, and die if
they do not have
access to maggots.

12. Hister beetles
Family name: Histeridae
They are among the first beetles to arrive at carrion.
They generally hide under a corpse during the daylight,
and only become active at night when they enter the
maggot-infested part of the corpse to capture and devour
maggots.
The adults feed on both the larvae and pupae of all
species of blowfly.
The adults lay their eggs in the corpse, and the larvae
feed on blowfly pupae when they emerge

13. Rove Beetles
Family name: Staphylinidae
They eat the fauna residing on and in a corpse
Adults are early visitors to a
corpse and they feed on larvae and eggs of all
species of fly, including predatory fly larvae.
They lay their eggs in the corpse, and the
emerging larvae are also predators.

14. Hide Beetles
Family name: Dermistidae
Late-arriving species tend to be specialist
scavengers which feed on tougher parts like
skin and tendons as the body dries out.
The dominant late stage scavengers include
the larvae of hide beetles
(Dermestidae).

15. Collection of entomological evidences
Entomological evidence collection is the process of
collecting evidence based on insect clues used in criminal
investigations. If evidence is not carefully preserved at a
crime scene after a death, it may be difficult or impossible
for an entomologist to make an accurate identification of
specimens, if for example, all morphological characteristics
are not preserved.

16. Forensic
Entomology Kit:
• Tackle box
• Larval forceps (thin and wide tip
forceps)
• Glass vials (20 ml or larger)
• Ethyl alcohol (80% or higher
concentration)
• Sweep net
• Rearing/storage containers for live
specimens (such as 16 oz plastic cups)
• Small bag of vermiculite
• Collecting pan (shoe box or anything
similar to sift ground samples)
• Disposable gloves
• Thermometer
• Small pieces of paper
• Pencils and permanent pens

18. Collect Live and Preserved Samples:
Be sure to collect representative samples of insect evidence as both live and preserved samples
Preserved samples include specimens placed directly into 80% (or greater) ethyl alcohol
 Fly eggs, larvae (maggots), pupae, newly emerged adults, etc.
 Adult beetles, beetle larvae, ants, etc.
 Adult flies collected using a sweep net can be: 1) placed directly into 80% ethyl alcohol; 2) anesthetized
using an insect kill jar and then placed into 80% ethyl alcohol; or 3) placed into labeled sandwich bags
and kept frozen until delivery of evidence to Dr. Watson.
Live specimens of fly eggs, larvae, and pupae from the same areas as the preserved samples place approx.
50-75 larvae of representative sizes on a food medium (raw hamburger, beef liver) and wrap loosely in
aluminum foil. Place the raw meat and larvae into a rearing container with ½ to 1“ of vermiculite.

19.  Be aware of the potential of placing too many eggs or young larvae into a
single container. If so, simply separated the live larvae into additional
containers, label and feed as specified.
 Be sure that the container lid is ventilated with very small holes to avoid
escaping larvae.
 Be sure to collect the LARGEST fly larvae present (or most mature larvae).
 Be sure to look for presence of fly pupae. Place pupae in a ventilated rearing
container with vermiculite (no raw meat needed).

20. • What is aquatic Entomology?
• Aquatic Entomology is the study of
insects that live in the water during all
or part of their lives. Many flying insects
such as dragonflies, damselflies,
caddisflies spend their larval youth in a
stream, where they are the primary prey
of fish.
Aquatic Entomology

21. Association of insects under aquatic habitat
Insects are usually
associated with corpses
both in terrestrial as well
as aquatic habitat and
proved to be very helpful
in estimating time of death
in past scenarios.
The succession of aquatic
insects species in the
aquatic habitat can play a
very crucial role in the
determination of PMSI.

22. PMSI
• Postmortem Submersion
Interval (PMSI) is defined
as the period between entry
into the water and recovery
of the dead body .
Determining PMSI has long
been problematic, since
factors due to aquatic
environments, such as algal
growth, adipocere formation
and water composition, can
affect the rate of post-
mortem decay.

23. Decomposition
The decaying stages in aquatic environments were first formulated by Megnin in 1894.
He classified these post-mortem changes into eight stages of decomposition and
discussed the association of various terrestrial entomofauna with each stage.
These stages were later reduced to five stages (Payne, 1965).
1. Submerged fresh
2. Early floating
3. Floating decay
4. Advanced floating decay
5. Sunken remains

24. First Stage: Submerged
Fresh
Fresh.

25. Second Stage: Early Floating
Pig carcass floats to
the surface.
Carcasses projecting
above the water
surface attract
terrestrial insect
species.
Decay odor was
quite evident and
pronounced.
Wire indentations on
carcass.
Duration: 2-10 days

26. Third Stage: Floating Decay
The skins started to slough off from both
the forelimbs and the hind limbs, and
the carcasses started to turn blackish.
The abdomen started collapsing because
of the release of gases, but the carcass
was still at the floating stage.
Wire indentations were still present.
Duration: 5-18 days

27. Fourth Stage: Advanced Floating Decay
Gas released though carcass remained
floating.
Most of the exposed tissues disappear
due to the continual feeding activities of
blow fly maggots.
As maggots mature, they started
migrating away.
Disarticulation of phalangeal and limb
bones.
Duration: 8-22 days

28. Fifth Stage: Sunken Remains
Only bones and bits of skin
present which became black.
Decay odor was negligible.
Various aquatic insect’s
larvae were present.
Duration: 9-19 days