Diptera & Coleoptera: Decomposition

Decomposers

  • Definition: A decomposer is an organism that breaks down dead or decaying material.

  • Role: Decomposers make up an essential part of our food chain as all species are nourished by death.

Detritivores

  • Definition: Organisms that obtain their nutrients by consuming detritus, specifically decomposing plants and animals along with their waste.

  • Process: Decomposition is described as the process of breaking down organic matter into simpler forms.

Insect Decomposers

  • Feeding: Insect decomposers feed on dead or rotten animals or plants.

  • Categories:

    • Those that feed on dead or drying plants.

    • Those that feed on dead animals (referred to as carrion).

    • Those that feed on excrement (also known as poop).

  • Taxa: Numerous insect taxa act as decomposers, including beetles, flies, termites, ants, wasps, and other flies, and they can consume a carcass rapidly.

Excrement

  • Attraction: Many insect species are attracted to the odor of animal excrement.

  • Example Species:

    • Manure flies and dung beetles are adults that lay eggs on fresh feces, with larvae using organic matter in waste products as nourishment.

Dung Beetles

  • Preference: Dung beetles exhibit a preference for herbivore manure types as they provide necessary nutrients.

  • Navigation: They search using olfactory cues and roll dung to be used as a brood chamber.

  • Reproductive Behavior:

    • Females lay eggs inside the dung and provision it for larval development.

    • Rolling quickly in a straight line is beneficial for reproductive success.

Dung Beetles & Milky Way Navigation

  • Night Navigation: Dung beetles navigate at night and require a compass to avoid going in circles.

  • Research Findings:

    • Beetles can utilize polarized light and maintain straight trajectories even in the absence of the moon.

    • Research conducted in a planetarium concluded that beetles were not using individual stars but a bright strip of stars for navigation.

Dead Animals

  • Necrophagy: This is defined as the feeding behavior on carrion of another organism that it did not kill.

  • Arrival of Insects: After death, the process of decomposition begins and insects can arrive within minutes.

  • Temporal Resources: Changes over time as different stages of decomposition become attractive to different species.

Suborder: Brachycera

  • Ecology: The ecology of Brachycera is diverse.

  • Dietary Habits: These insects generally feed on soft or liquid food and lack the capability to chew.

  • Modification: Maggots are modified to live within their food source.

Diptera: Brachycera

  • Morphology:

    • Characterized by large compound eyes and varied mouthparts related to decomposing matter.

    • Mouthparts include sponging mouthparts, antennae with lateral bristle, labium, maxillary palps, eye structures, and labellum.

Brachycera: Larvae

  • Larval Characteristics:

    • All Brachycera larvae are legless and commonly referred to as maggots.

    • They have mouth hooks and are limbless with terminal abdominal spiracles.

  • Species Examples:

    • Calliphora sp, Chrysoma sp, Lucilia sp, Sarcophaga sp, Chrysoma rufifacies, Gasterophilus sp, Musca sp.

Importance in Ecosystems

  • Food Web Role: Brachycera larvae play important roles in food webs both as prey and decomposers.

  • Medical Applications: Larvae are crucial in medical settings for wound healing.

Larval Ecology: Medicine

  • Maggot Use: Maggots are employed in a medical setting, specifically in wound healing.

  • Maggot Debridement Therapy: This involves using larvae to remove necrotic tissue from wounds.

Wound Healing Process

  • Action: Larvae treat wounds by consuming necrotic tissue.

  • Properties:

    • They possess antibacterial properties that inhibit secondary infections.

  • Circulation: The movement of maggots promotes circulation in the treated area.

Maggot Debridement Therapy Details

  • Cost-Effectiveness: This therapy minimizes costs and the need for invasive procedures.

  • Rearing: Larvae are reared in sterile environments.

  • Application: Larvae are placed in a dressing to prevent escape and only feed on necrotic tissue.

Parasitic Maggots

  • Definition: Parasitic maggots can infest living tissue, a condition referred to as myiasis.

  • Process: This occurs when eggs are deposited on a host, hatching into larvae that burrow into the skin.

Pest Characteristics

  • Livestock Pests: Parasitic maggots serve as pests to livestock and can also infect humans.

  • Discomfort: The spines on the larvae cause extreme discomfort in the affected individuals.

  • Removal: They can be removed by obstructing their breathing channels and extracting with forceps.

Livestock Pests

  • Example Species: Screw worm (Cocholiomya sp.) infests exposed soft tissues such as wounds.

  • Behavior: They burrow deeper into tissue when disturbed, leading to severe damage.

Impact on Livestock

  • Consequences: Infestation can lead to killing an animal due to severe tissue damage.

  • Eradication: The screw worm was eradicated using the Sterile Insect Technique in 1982 but re-emerged in 2016.

Necrophagous Insects

  • Egg Laying Behavior: Necrophagous insects lay eggs directly on their food source.

  • Parental Care: Adult insects display a basic form of parental care by ensuring their offspring's nutrition.

Decomposers: Necrophagy

  • Role: Necrophagous insects that consume dead or decaying animal matter play a fundamental role in terrestrial ecosystems.

  • Forensic Applications: Their behavior can be utilized to determine the time of colonization at a crime scene.

Forensic Entomology

  • Definition: Forensic entomology is the application of insect and arthropod studies to legal issues.

  • Areas of Application:

    • Urban (criminal and civil matters).

    • Stored product (civil matters).

    • Medico-legal (criminal matters).

Medico-Legal Forensic Entomology

  • Nature: This aspect is criminal in nature and relates to insect activity in murder, rape, or suicide cases.

  • Investigation Focus: Observes insect presence that assists in decomposing deceased bodies.

Objective of Medico-Legal Forensic Entomology

  • Cases: Investigates cases involving suspicious deaths where insects are discovered on decomposing corpses.

  • Estimation: Insect colonizers can estimate the interval between death and corpse discovery, known as postmortem interval (PMI).

Forensic Entomologist's Interests

  • Investigative Focus: The species of insect present at a crime scene is critical.

  • Timing: Specific species appear at certain locations and times, which can be vital in investigations.

Insect Succession

  • Definition: Succession refers to the pattern of insect colonization as decomposition progresses.

  • Data Collection: Information on the abundance of taxa, life stages, and number of individuals is gathered from studies.

Development Time

  • Importance: The development time of insects at a crime scene is important for estimation.

  • Predictable Growth: Insects grow at predictable rates, which can indicate the time of death.

Murder Investigations

  • Focus: Examines specific insects arriving at the body to lay their eggs.

  • Assessing Evidence: Forensic entomologists assess the body and the order of insect appearance to determine the time of colonization and thus estimate time of death.

Criminal Forensics

  • Common Species: A subset of species, such as blow flies and dermestid beetles, are commonly involved in forensic issues.

  • Research Data: These species have been extensively studied, providing statistically reproducible information relevant to forensic entomology.

Growth of the Discipline

  • Interest: Increased output of research articles and the publication of introductory books has fueled growing interest in forensic entomology.

References for Further Reading

  • Forensic Entomology: The Utility of Arthropods in Legal Investigations, Third Edition, by Dorothy Gennard.

  • Forensic Entomology: An Introduction, Second Edition, by David B. Rivers, Gregory A. Dahlem, edited by Jason H. Byrd, Jeffery K. Tomberlin.

  • The Science of Forensic Entomology, edited by Jason H. Byrd & James L. Castner.

Questions?

  • Explore additional entomology courses:

    • 11:370:424 Insect Behavior

    • 11:370:250 Insects & the Environment