Chapter 7 Forensic Entomology

Medical Entomology

The study of the insects associated with a body

What can entomology be used to estimate?

The minimum elapsed time since death from the moment of death up to a year or sometimes longer after death.

What are the two methods used to estimate elapsed time since death?

1. The predictable development of blow flies

2. The predictable successional colonization of the body by a sequence of carrion insects

How to estimate time since death using blow flies?

Using the known passage of time from when the first egg is laid on the remains until the first adult flies emerge from the puparial cases

T or F. Insects colonize humans exactly the same way the colonize a dead animal

True

What are the first insects attracted to remains?

True flies (Diptera)

What do blow flies primarily feed on?

Sugary food sources (nectar) and protein (feces, carrion)

What do maggots and larvae feed on?

Dead animals

Why do female blow flies have the ability to locate a body immediately after death?

Because their maggots survive best in fresh bodies

T or F. Blow flies are not diurnal, they are active all day/night

False (not active at night)

Why are blow flies attracted to the wound first?

Because the blood is an excellent and easily obtained protein source for the maggots

T or F. Blow flies can locate a venipuncture even when it is no longer visible to the naked eye

True

If there are no wounds, where do insects colonize?

In natural orifices

First-instar

First-stage fly larvae that cannot penetrate skin and must feed on liquid protein

Second-instar

Second-stage fly larvae that shed the first-instar larval cuticle and mouthparts

Third-instar

Third-stage fly larvae that shed the cuticle and mouthparts. They frequently aggregate into large masses

Why are newly emerged flies of great forensic significance?

They indicate that an entire blow fly life cycle has been completed on the body

T or F. Once a fly is dried and can fly it can be linked directly back to the remains

False

What do empty puparial cases indicate?

An insect has completed its entire life cycle on the body

What is the second method of estimating elapsed time since death?

Based on predictable successional colonization of the body by a sequence of carrion insections. ( can be used from a few weeks after a death to dry bones)

The four factors that must be known when estimating time since death using blow fly development?

1. The oldest stage of blow fly associated with the body

2. The species of insect

3. Temperature data

4. Developmental data (rate of development)

The first step when studying a variety of insects found on remains

Identifying the species that are present at that time

What else can insects be used for at a death scene? (Other than elapsed time since death?)

Can be used to indicated whether a body has been moved after death. If the body has been disturbed. Locating the position of wounds. If the person used drugs. Linking a suspect to a scene.

What should an entomologist do if tissues like blood, liver kidney etc are degraded and cannot be drug tested?

Analyze the insects feeding on the body

Bioaccumulation

The process of substances building up over time in an organism

What will an analysis of insects feeding on a person with a drug history show?

What drugs were present, but not the amount that was ingested

What role does DNA have with insects?

Identifying an insect and using insects to retrieve DNA from the victim when the victim's DNA is no longer available

Myiasis

The infestation of living human or other vertebrate animals with dipteran larvae

When are insects analyzed on an alive victim?

To estimate the length of time that has passed since the person was wounded or neglected

Maggot debridement therapy

The purposeful use of maggots on living patients to remove dead tissue

What does a lack of insects on a body mean?

It is too early in the year for insects to be able to colonize, it's too cold, or the body has only been at the death scene for a short period of time

What is one of the most important factors that impact insect development?

Temperature

What does it mean if remains are found in the winter and show signs of insect activity?

The death must have occurred prior to onset of the cold season