L2 - Insects associated with decomposition of body

What do files (diptera) do when they find a body?

• egg laying rather than feeding

• •the acidic tissues of a fresh corpse cannot be digested by flies.

What neutralises the acidic tissue/fluid of a corpse?

•Activity of

– bacteria,

–and the excretions of fly larvae feeding on exuded fluid

Makes it attractive to:

1. Blowflies

2. fresh flies

3. house flies

What are pioneer flies?

= first to arrive

1. Blowflies - Calliphoridae

2. House flies - Muscidae

Why do diptera arrive before beetles?

•Have great powers of dispersal

•Rapidly discover bodies

•usually ahead of the beetles in colonisation of body.

What do •Calliphoridae (blowflies) and Muscidae (house flies) & larvae feed on?

1. feed on bodies fluids

2. enter through natural openings/ wounds - feed over whole body as tissue decays

Why are calliphoridae important?

• Primary insects most commonly associated with corpse

• invade minutes after dead

• colonise the body more rapidly & greater numbers than other

• most accurate info regarding PMI

3 main genus of family calliphoridae

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What are the biomarkers that attract blowflies?

•Bacteria break down tissues and cells, releasing fluids into body cavities.

•Anaerobic putrefactive processes produce various gases incl. hydrogen sulphide, methane, cadaverine and putrescine as by-products.

•The build up of gas resulting from the intense activity of multiplying bacteria results in purging of fluids from cells and blood vessels

How far away can blowflies pick up scents ?

20km from birth place

Life cycle of blowflies

How would you identify blowfly eggs?

• are pale yellow or white in colour

• 2 mm long

• laid in clumps that resemble miniature rice balls.

• maggot becomes lethargic

In warm weather how long would it take for maggots to consume a body?

Can consume 60% of body in less than a week

What is first oviposition?

When eggs first laid

How can oviposition be used as an indication of trauma?

• When found at sites other than body orifices

• Location of insects on body can tell us where maggots start to feed

What do maggots do when they move throughout a body?

Secrete bacteria, digestive enzymes

tear tissue with mouth hooks

make conditions beneficial to bacteria

What happens when the rate of decay increases?

–and the smells and body fluids that begin to eminate from the body attract more blowflies, flesh flies, beetles and mites.

What are later arriving flies and beetles?

Predators feeding on maggots + decaying flesh

What do parasitoid wasps do?

Lay eggs inside maggots & pupae

How do maggot masses heat a corpse?

Through intense digestive activities

How much do maggot masses heat a corpse?

53 degrees

What does a maggot mass benefit from? What does this lead to?

communal heat

shared digestive secretions

leads to:

increased rate of putrefaction & digestion

Where does a maggot mass migrate to when it gets too hot?

to the edge to cool down