Forensic Entomology Flashcards

Forensic Entomology

• The legal application of the study of arthropods

• Arthropods: Invertebrate animals with jointed legs, including:

  • Insects

  • Arachnids

  • Centipedes

  • Millipedes

  • Crustaceans

Entomology Types

• Urban Entomology:

  • Deals with pests in human environments like cockroaches and termites.

  • Also includes issues in cattle & poultry feed houses.

• Stored Product Entomology:

  • Focuses on arthropods found in food and other products, such as restaurant contamination.

• Medicocriminal Entomology:

  • Involves arthropod evidence in crimes, particularly violent ones.

Forensic Entomologist Questions

• Two common questions:

  • Time since death, known as Postmortem Interval (PMI).

  • Where the death occurred.

Insects

• Most numerous and diverse group on the planet.

• Characterized by:

  • Six legs.

  • Body divided into three regions: head, thorax, and abdomen.

• Found in almost all terrestrial habitats and most aquatic ones, except for salt water.

Insect Lifecycle

• Pass through a series of stages developing from an egg to an adult.

• Four distinct stages:

  • Egg

  • Larva

  • Pupa

  • Adult
    *The appearance of these stages and the time spent in each varies with the species and environmental factors

• Accurate climate data is important

• As the temperature increases so does the development rate (usually)

Identification Importance

• Proper identification of insect / arthropod species is the most important aspect of forensic entomology

• Identification allows for proper development data and distribution ranges to be applied

Flies

• Over 16,000 species in North America.

• Important scavengers, removing decomposing plant and animal material.

Flies Commonly Encountered

• House fly

• Blow fly

• Horse fly

• Most flies associated with corpses have spongelike mouthparts

Fly Lifecycle Details

• Begin life as eggs laid in large numbers on decaying material.

• When hatched they are at the food source

• Young maggots pass through three stages before pupating.

Fly Pupation

• Mature maggots migrate away from the food source.

• Pupate in soil, clothing, or indoors (furniture, carpet).

• Molt with skin shrinking and hardening, forming a puparium, which is brown, reddish brown, or black.

Beetles

• Over 30,000 species in North America.

• Larva are called grubs.

• Dermestid beetles of forensic importance:

  • Larder beetles

  • Carpet beetles

  • Hide beetles

• Can be responsible for significant amount of damage

Beetle Behavior

• Larva usually present during dry and skeleton stages.

• Can skeletonize a body in under a month.

• Will move away from light and hide in recesses or cavities.

Beetle Characteristics

• Adults are cannibalistic and may eat larva and pupa.

• Presence of frass is proof they have fed heavily on tissues, indicating a considerable time lapse since death.

Scavengers

• Some scavengers will feed on carrion as an opportunistic food source

• Cockroaches have been known to feed on carrion if in unsanitary conditions

Insect Colonization

• Insects are the first to arrive on a body after death and they colonize in a predictable sequence

• As the body moves through different stages of decomposition it becomes appealing to different groups of insects

• Blow flies are the first colonizers and can be attracted by odors from great distances

Egg Laying and Maggot Mass

• Eggs laid in large numbers

• Large maggot mass brakes down body faster

• Can generate their own heat to protect against temperature drops

Blow Flies Activity

• Blow flies are diurnal and usually rest at night so it is uncommon for eggs to be deposited during this time

• Insects, maggot masses have been known to move / tear clothing

Insect Colonization Factors

• Most important factor is biogeoclimatic zone:

  • Habitat, vegetation, soil type, meteorological conditions.

• Time of colonization depends on geographic location:

  • Data from one zone cannot be used in others.

• Season also impacts rate of colonization:

  • Insects have peak seasons of activity.

Post Mortem Interval (PMI) Evaluation

• Presence or absence of a species as an indicator of the time of death, based on understanding of succession patterns

• Evaluate degree of development of insects present on body

• Factors used to evaluate PMI:

  • Species characteristics

  • Weather and seasonality

  • Food type

  • Drugs and other toxins

  • Geographic region