Transcript ENT 561 – Insects affecting human and animal health

ENT 561 – Insects affecting
human and animal health
Introduction … continued
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
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
In many cases, man has
worsened problem
• Increased population densities
• Expansion into new areas
• Environmental Modification
• Artificial Selection
Survey Results: Class Make up
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Questionaire Answer
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Introduction to the Insects
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.
Introduction to the Insects
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.
Insect Species Composition
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.
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”.
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.
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
Classification of insects
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
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
Distinguishing Features of Insects
vs. Other Arthropods
Legs
Antennae
Body
Divisions
Wings
Insects
Arachnids
Crustaceans
Centipedes
Millipedes
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Distinguishing Features of Insects
vs. Other Arthropods
Legs
Antennae
Body
Divisions
Wings
Insects
Arachnids
Crustaceans
Centipedes
Millipedes
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Head
Head - Mouthparts
Mouthparts have evolved in many
ways.
Insect Head: Antennae
• Antennae are
primarily chemical
(& sometimes
sound) receptors
• Three basic
segments: the
scape, pedicel
and flagellum
• Flagellum made
up of multiple
flagellomeres
Many basic types of antennae
Aristate - pouch-like with a
lateral bristle. Eg. House flies.
Filiformis - thread-like
shape. Eg. Cockroaches.
Serrate – saw toothed
shape. Eg. Click beetles
Capitate - abruptly clubbed
at the end. Eg. Butterflies.
Geniculate - hinged or bent
like an elbow. Eg. Bees/ants.
Plumose - brush or feather-like
shape. Eg Moths and mosquitoes.
Clavate - gradually clubbed at
the end. Eg Carrion beetles
Monoliform - bead-like in
shape. Eg Termites.
Setaceous - bristle-like
shape. Eg Dragonflies.
Insect Body: Thorax & Abdomen
Dorsal = Topside
Ventral = Underside
Insect Legs
Wings
Generic Mosquito Wing
Internal Anatomy
Insect Cuticle
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)
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
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.
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
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.
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.
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
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