ent 561 – insects affecting human and animal health introduction … continued
TRANSCRIPT
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ENT 561 – Insects affecting human and animal health
Introduction … continued
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Peripheral Damage
• Quarantine and Restrictions
• Medical treatment problems (incorrect, treatment avoidance, etc.)
• Contamination
– Blood Donations
– Food Contamination
• Societal Costs
– Associated with damage
– Associate with damage prevention measures
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In many cases, man has worsened problem
• Transportation of arthropods
• Transportation of pathogens • Transportation of pathogens in humans
• Transportation of pathogens in livestock, insects, other animals
• Justinian created the first plague: “Without the empire, the bread dole, the huge shipments of grain and cloth from Africa, it is difficult to imagine how the First Pandemic could ever have erupted.” Orent, 2004
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In many cases, man has worsened problem
• Increased population densities
• Expansion into new areas
• Environmental Modification
• Artificial Selection
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Survey Results: Class Make up
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15
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mb
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Fr SoJr Sr O
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MSc
PhD
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Survey Results: Major
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Animal Sci
Biology
Entomology
Non-Deg
Biotech
Pre-Vet/Med
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Survey Results: Level of Entomological Understanding
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4
8
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mb
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1 2 3 4 5
Questionaire Answer
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Introduction to the Insects
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Introduction to the Insects
The oldest known insect -- Rhyniognatha hirsti – known from a single fossil, 400 million years old. This is shortly after plants colonize land and this appears to be a herbivore.
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Introduction to the Insects
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Life on earth as a speciescape:
• About 1 million of the 1.1 million animal species are insects
• Estimates range from 5 to 80 million insect species are currently in existence.
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Insect Species Composition
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Reasons for insect success• Small size -there are many more niches for small organisms than for large
organisms. For instance, one insect could live solely on and in the seeds of a specific plant.
• Short life cycle - this allows many generations within a given time for selection and evolution to take place.
• Large reproductive ability - large numbers of offspring support a large variation for selection and evolution to act upon.
• Variation in the life style of different stages in an insect's life (e.g. caterpillar versus butterfly) reduces competition for resources within the species.
• Wings-the ability to fly is relatively rare outside insects and has allowed them to colonize freely.
• Sensory sophistication - the sensory capabilities of insects surpasses most other organisms.
• Evolutionary interactions with other organisms - coevolution leads to greater specialization and speciation.
• Adaptation of appendages - mouthparts, wings and legs have often become highly specialized.
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Insects just are
• They are neither good nor bad
• They are not here to serve a purpose – They evolved here in response to selective pressures
• Only man thinks of insects as “beneficial” or “detrimental”.
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Some benefits of insects• Plant pollination - Pollination by animals is more effective than by
wind. Most higher plants are pollinated by animals, usually insects such as bees, wasps, flies and beetles.
• Production of products - honey, bees wax and royal jelly, silk (produced by the caterpillar, Bombyx mori), shellac (a varnish produced by a plant bug), cochineal (red food coloring produced by a plant bug) and 'Spanish fly' (a beetle and supposed aphrodisiac).
• Nutrient recycling - by detritus and dung feeders and particularly in Australia by termites.
• Maintenance of an ecological food chain in many systems.
• Human food - over 500 species of insects are used as food by humans -usually crickets, grasshoppers, beetle and moth larvae and termites. Miscellaneous - Indigenous peoples (e.g. from PNG) often used butterflies and brightly colored beetles as head or body decoration. Insect collecting is a common Western hobby and there is a small industry in arthropod pets.
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Detrimental effects of insects
• Destruction or spoilage of food (both fresh and stored) and crops (including forests)
• Damage to goods - leather, paper, textiles, (by beetles, cockroaches, silverfish or moths), timber & structures (by termites, some ants, different sorts of borers)
• Direct disease of humans or livestock • Disease vectors • Venoms, allergies, urticating hairs• Nuisance value - flies, ants • Phobias - such as arachnophobia
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Classification of insects
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Common Names of Insects
• Very commonly used by scientists and laymen alike.
• Often more descriptive than the scientific names e.g. “Yellow Fever Mosquito”
• No scientific validity.
• For Insects, most names are set by the Entomological Society of America
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Features of Arthropods
• Exoskeleton - a hard protective covering around the outside of the body (divided by sutures into plates called sclerites)
• Segmented body - that allows movement • Jointed limbs and jointed mouthparts - that allow
extensive specialisation • Bilateral symmetry - whereby a central line can divide
the body into two identical halves, left and right • Ventral nerve chord - as opposed to a vertebrate nerve
chord which is dorsal • Dorsal blood vessel
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Distinguishing Features of Insects vs. Other Arthropods
Insects Arachnids Crustaceans Centipedes Millipedes
Legs 6 8 Variable 1 pr/bs 2 pr/bs
Antennae 1 pr 0 2 pr 1 pr 1 pr
Body Divisions
3 2 Variable Many many
Wings 2 pr 0 0 0 0
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Distinguishing Features of Insects vs. Other Arthropods
Insects Arachnids Crustaceans Centipedes Millipedes
Legs 6 8 Variable 1 pr/bs 2 pr/bs
Antennae 1 pr 0 2 pr 1 pr 1 pr
Body Divisions
3 2 Variable Many many
Wings 2 pr 0 0 0 0
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Head
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Head - Mouthparts
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Mouthparts have evolved in many ways.
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Insect Head: Antennae
• Antennae are primarily chemical (& sometimes sound) receptors
• Three basic segments: the scape, pedicel and flagellum
• Flagellum made up of multiple flagellomeres
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Many basic types of antennae
Aristate - pouch-like with a lateral bristle. Eg. House flies.
Capitate - abruptly clubbed at the end. Eg. Butterflies.
Clavate - gradually clubbed at the end. Eg Carrion beetles
Filiformis - thread-like shape. Eg. Cockroaches.
Geniculate - hinged or bent like an elbow. Eg. Bees/ants.
Monoliform - bead-like in shape. Eg Termites.
Serrate – saw toothed shape. Eg. Click beetles
Plumose - brush or feather-like shape. Eg Moths and mosquitoes.
Setaceous - bristle-like shape. Eg Dragonflies.
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Insect Body: Thorax & Abdomen
Ventral = Underside
Dorsal = Topside
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Insect Legs
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Wings
Generic Mosquito Wing
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Insect Cuticle
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Insect Life Cycles -- Ametabolous
• Like almost all insects, start with eggs.
• Immatures have the very same shape as adults
• Seen in the most primitive, wingless groups (not medically important)
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Insect Life Cycles -- Hemimetabolous
• Start with an egg
• Immatures have similar shape with adults EXCEPT wings.
•Wings develop externally to body
•Immatures often live in the same habitat as adults
• Includes the more primitive winged groups (Bugs, Dragonflies, Grasshoppers, Roaches
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Insect Life Cycles -- Holometabolous
• Start with an egg.
• Immatures have a very different shape from adults
• Body transition occurs in pupal stage.
• Pupal stages often double as a survival stage.
• Larvae and adults often inhabit different niches
• Includes the most advanced insects: flies, beetles, moths/butterflies, bees/ants, fleas.
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Insect Development and Weather -- Light
• May control vegetation and therefore insect populations
• Important in orientation.
• Used for inflight control – especially for night-flying insects
• Photoperiod -stimulus for diapause initiation
• Many insects are nocturnal or diurnal
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Insect Development & Weather - Temperature
• Body temperature of insects governs rate of growth
• Most insect activity and reproduction occurs between 15 -35o C
• Different stages may have different rates of development.
• Surviving extreme temperatures often requires special adaptations in physiology, behavior, etc.
• Understanding the relation between development & weather enables us to predict activity/threat level.
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Insect Development & Weather - Wind
• Indirect effect causing evaporation, humidity and so desiccation
• Dispersal e.g. aphids, moths grasshoppers
• Often affects activity levels esp. for weak fliers.
• Affects distribution of olfactory stimulants for feeding, oviposition, and mating.
• Primarily a factor for adults.
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Insect Development & Weather - Moisture
• Sometimes affects development directly.
• Rain important for those species that need ephemeral aquatic habitats.
• Humidity important as an antidessicant.
• Often interacts with temperature
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When populations are too big, they must be controlled.
• Cultural – Habitat manipulation• Mechanical/Physical – swatting/picking,
exclusion, environmental manipulation, etc.• Biological – Using one species to control
another: Predators, parasitoids, pathogens
• Genetic – Applying a control on F1 which is expressed in F2 or later.
• Behavioral – Modifying the behavior• Chemical – Using lethal chemicals