Lecture 2 - Basic
Entomology
…
Housekeeping
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Course Page
http://www.esf.edu/efb/parry/fsc 462_662_Home.htm
I will post all lecture/lab material as PDF’s which you can
download or read online.
(Lecture 1 is online)
Pig 2
N
Pig 1
Lab
Parking
Classroom
www.bioquip.com
Entomology
Study of Insects (Phylum Arthropoda,
Class Insecta)
l  ENTOMOLOGY Greek entomon insect,
‘one whose body is cut into segments’
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MANY and sundrie sorts there be of Insects, as well among land creatures as
those that flie in the aire. Some are winged, as Bees: some have partly
wings and partly feet, as Pismiers: others want both, and neither flie nor
goe on their feet. And well may they all be called Insecta: by reason of
those cuts and divisions, which some have about the necke, others in the
breast and belly; Pliny the Elder (77 A.D.) Historia Naturalis
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Phylum Arthropoda (jointed foot)
Centipedes/Millipedes
Spiders/Mites/Ticks
Horseshoe Crabs
Insect Taxonomy
Classification of the forensically important
black blowfly
l  Kingdom: Animalia
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Phylum: Arthropoda
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Class: Insecta
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Order: Diptera
§  Family: Calliphoridae (The Blowflies)
§  Genus: Phormia
§  Species: regina
§  Common name: black blowfly
The Insects
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Most diverse group of organisms on the planet.
Most successful organism that has ever lived
750,000 described species
At least a million or more undescribed species
(estimates range from 1M-30M)
Earliest confirmed insect fossil ~ 400 MY before
present
Key to success
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First major terrestrial animal group
Flight!!!
Overview
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Occur on every continent including Antarctica
Virtually all habitats and temperature range
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Heat
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Cold
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Arctic beetle (-87C)
Oceans are the exception.
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Desert ants (60C) chironomid midges in hot springs (50C)
Why not in oceans?
Size
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0.1mm - 16.7 cm
Titan and Goliath beetles, giant weta
What limits upper size?
Characteristics of Insects
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Six legs (all may not be present in every
stage or may have been secondarily lost in
evolution)
Bi-lateral symmetry
Three body parts (regions)
Single pair of antennae (may be small)
Exoskeleton
Wings: May be present (1 or 2 pairs)
absent, secondarily lost, or present in only
some generations
Insect Body Plan
Three major body regions: head, thorax, abdomen
Mouthparts
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Chewing: has mandibles
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Piercing/sucking: modified into
a tube with a dagger
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Hemiptera, Homoptera, some flies
(e.g., mosquitoes).
Sponging –
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e.g., ants, beetles, grasshoppers
Houseflies
Siphoning – retractable straw
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bees, butterflies
Insect Growth
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With adequate food, growth is temperature dependent
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As temperature increases above a thermal minimum, growth
increases up to some thermal maximum
Growth is constrained to discrete stages by the hard exoskeleton.
Once a maximum size is reached in a particular juvenile stage,
further growth requires a molt.
Upper
Threshold
Lower
Threshold
Development
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Apterygota (Ametabolous)
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Juveniles look like miniature versions of adults. At
each molt, become larger until sexual maturity. Both
adults and juveniles are Wingless.
Exopterygota = Hemimetabolous
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Juveniles look like miniature adults without wings.
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Exceptions: some ancient aquatic orders (mayflies,
dragonflies, stoneflies)
Wings develop externally as pads. Wings grow larger
with each molt until sexual maturity
Endopterygota = Holometabolous
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Juvenile form very different than adult. A pupal
stage occurs between the larval and adult stages.
Wings develop internally.
Development Visualized
Larval types
Pupal Types
Survey of Relevant Insect Orders
Those with species of forensic importance
l  Those with species often present or
recovered during forensic investigation
l  Terrestrial:
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Outdoor
Indoor
Buried
Aquatic
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Freshwater
Marine (no insects of forensic importance)
Functional roles of Insect Associates of Cadavers
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Obligate necrophages – examples, blowflies, some beetles
Facultative necrophages – ants, cockroaches, some flies, some beetles
Natural enemies of necrophages – yellowjackets, ants
Adventives – accidental species with no actual feeding relationship with cadaver
Omnivores
Predators /
Parasites
Necrophages
Adventives
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Outdoor
l  Colembola
l  Dermaptera
l  Coleoptera
l  Diptera
l  Lepidoptera
l  Hymenoptera
Buried
l  Diptera
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Aquatic
l  Plecoptera
l  Ephemeroptera
l  Hemiptera
l  Coleoptera
l  Diptera
l  Trichoptera
Ecological Roles
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Indoor
l  Blattaria
l  Dermaptera
l  Coleoptera
l  Diptera
l  Hymenoptera
Primary carrion feeders (obligate necrophages)
Facultative carrion feeders
Associates (predators, herbivores, parasitoids)
We will discuss specific families within
orders (and important individual species)
as the course progresses.
Terrestrial
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Outdoor
l  Colembola
l  Dermaptera
l  Coleoptera
l  Diptera
l  Lepidoptera
l  Hymenoptera
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Indoor
l  Blattaria
l  Dermaptera
l  Coleoptera
l  Diptera
l  Hymenoptera
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Buried
l  Diptera
Order Collembola: Springtails
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Very primitive
l  Minute size
l  Furcula = “springtail”
l  Moist habitats
Order Blattaria: Cockroaches
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Terrestrial
Indoor and outdoor (mostly
further south) species
Scavengers, omnivores
Dermaptera: Earwigs
• Terrestrial scavengers and/or predators
• Damp locations
• Pinching cerci and greatly shortened wings
Order Coleoptera: Beetles
• Diverse ecological roles (predators,
parasites, herbivores, scavengers)
• Aquatic, terrestrial
• Second most important forensic
insect order
Order Diptera: True flies
•  Very ecologically diverse
• Diptera are the most widely used insect order
from a forensic standpoint
• Multiple families in terrestrial habitats
• Chironimidae, Simuliidae and perhaps a
few others in aquatic systems
Order Hymenoptera
•  Bees, ants, wasps, sawflies
•  Predators, parasites, herbivores
•  Greatest diversity è parasitoids
•  Ants can function as predators or
scavengers
•  Social wasps are predators on
maggots
Aquatic vs. Terrestrial Systems
•  No highly specialized carrion feeders
(that have been conclusively
demonstrated)
•  Mostly opportunistic feeders or
species that utilize the cadaver as a
substrate.
Order Ephemeroptera:
Mayflies
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Aquatic nymphs, terrestrial
adults, mostly grazers
No clear forensically important
role – likely an associate only
Order Plecoptera: Stoneflies
•  Aquatic nymphs, terrestrial adults
•  Predators, herbivores, detritivores
•  Different functional roles – but
probably primarily grazers on
attached algae etc.
Order Hemiptera
Diverse: Aquatic systems mostly
opportunistic scavengers (Corixidae,
Notonectidae, Gerridae)
May play a minor role in aquatic
decomposition of large carrion /
cadavers
Order Trichoptera
Caddisflies
•  Along with chironimid dipterans, probably
the greatest potential for use in a forensic
setting
•  Some appear to be directly linked to
decomposing flesh (function as a
necrophage?).
Decomposition in a Marine Ecosystem