Entomology Flashcards
What is forensic entomology?
The use of insects in legal investigations
What are the areas of application of forensic entomology?
- urban entomology
- stored product entomology
- wildlife/veterinary entomology
- medico-criminal entomology
- criminal law
What is the main application of entomology?
Criminal law
Areas of application: urban entomology
- insect damage
- agricultural pests
Areas of application: stored product entomology
- food contamination
- biosecurity issues
Areas of application: wildlife/veterinary entomology
- animal welfare/cruelty
- wildlife death/poisoning
- illegal poaching
Areas of application: medico-criminal entomology
- suspicious death
- death scene investigation
- entomo-toxicology
- negligence
- child abuse
- drug trafficking
Areas of application: criminal law
- suicide, homicide or unknown cause
- body not always found straight away
What is the key entomological information requires in forensic entomology?
Post-mortem interval
What is establishing an accurate PMI important for?
- reconstruction of events
- links between a suspect and victim
- credibility of witnesses
How can insects provide an estimate of PMI?
- insects are attracted to remains very soon after death through the detection of chemical odours released by the body
- human remains offer a new habitat for colonisation by insects
- the body can offer a food source for offspring, an extension of habitat or hunting ground for other insects
What are the 2 principles of PMI?
Principle 1: temperature-dependent development of insects (based on the known relationship between insect development and temperature)
Principle 2: predictable arrival of insects colonising the body
What is ametabolous insect development?
- egg hatches into a smaller immature version of the adult
- undergoes a series of malts to grow in size
- little or no difference in appearance between adult and young
- only major difference is absence of reproductive organs in young
- generally have no wings
What is an insect that undergoes ametabolous development?
Silverfish
What is hemimetabolous development?
- consists of 3 primary stages: egg stage, nymph stage and adult stage
- nymphs look like adults, but usually don’t have wings and have under developed reproductive structures
What are some examples of insects that undergo hemimetabolous development?
Grasshoppers, dragon flies, earwigs
What determines PMI?
Age of oldest specimen
What is holometabolous development?
- egg is laid by an adult
- egg hatches into larva or nymphs
- nymph has a very different habit and shape than adult form
- no competition of resources between larva and adult
What are some examples of insects that undergo holometabolous development?
Butterflies, blowflies
What are the larvae of blowflies known as?
Maggots
How many malts does a blowfly under go?
- 3
- can be determined by number of pairs of spiracles
What does an entomologist require?
- specimens collected
- specimens identified
- lifestage identified (oldest used)
- development data for that species
- weather data associated with remains
What is ecological succession?
Predictable and orderly changes in composition or structure of an ecological community over time
What do necrophagous species do?
- attracted to the body as a food source for themselves and offspring and feed directly on the body
- typically 1st to arrive at body and usd for PMI estimation
- eg blowflies and beetles
What do predators and parasites of necrophagous species do?
- attracted because of food and host opportunities
- eg beetles, wasps and larvae of a few other blowfly species (predate on larvae)
What do omnivorous species do?
Eat the body and other insects
What do adventive species do?
- colonise decomposing body as an extension of their natural habitat
- can occur due to chance, proximity to body or attraction to body for shelter and concealment purposes
- can indicate movement of body
- eg dungbeetles
How is early post-mortem calculated?
- age of the oldest insect larvae collected
- adult arrival time interpreted in relations to known patterns of insect succession
How is late post mortem calculated?
- composition of the anthropoid community in relation to the expected succession pattern
How are eggs collected from the body?
- collected live
- should be placed in separate containers depending on where found in the body
- placed in cooler to slow growth
- 2 groups
- half preserved
- half placed on meat food source and reared to adulthood for identification of species
How are larvae collected?
- split into 2 samples
- half preserved by killing them in just off the boil water and then placed in ethanol solution (this prevents shrinkage - measurements of length are important)
- larvae must be separated as some will kill each other
How is temperature history determined?
- weather station placed at crime scene for a week or more
- records temperature and humidity
- data is compared to data from a local weather station and a correction factor is identified
- this allows use of weather station records prior to discovery of the body to be corrected for slight differences and is used to determine insect development
How are pupae collected?
- split into 2 groups
- for preservation pupae are pricked using a sharp pin at both ends of the pupil casing to create holes for fluid perforation directly into the metamorphosing tissue
- places in 70% alcohol
Empty pupae cases can be used to…….
Indicate species
Why are pupae often hard to find?
- can a range in size from 2-20mm
- easily confused with bark or rocks
- blowflies actively burrow before forming pupae
- blowflies can travel several meters from body before forming a pupae
Therefore soil samples are taken
What are the stages of decay?
- fresh
- bloat
- wet decay
- dry decay
- skeletal
Which animals are attracted to the body at which stages of decay?
- fresh: primary colonising fly species (lay eggs around openings)
- bloat: Sulfur compounds attract flies, beetles
- wet decay: secondary adult colonising fly species, predatory beetles, parasitic wasps
- dry decay: flies no longer predominant insect, tertiary colonising species arrive, beetles predominate (and predators with larvae)
- skeletal: no necrophagous species, adventous species predominate
Identification of insect species that are not commonly associated with the location of the death scene suggests:
Post-mortem movement of the body
What happens when temperatures exceed the optimum for insect development?
Development is negatively affected until death occurs
Maggots undergo 3 stages of growth known as:
In stars
The first written report of the use of insects in legal investigation occurred in which country?
China
True or false: smooth and hairy maggots should never be placed in the same container
True
