Insect mimicry

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Transcript Insect mimicry

Insect biology
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The science that deals with insect’s individual
developmental history.
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It is divided into the study of reproduction,
embryology, post
embryology and adult
Larval stage or nymph stage
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Stage: hatching from egg to the adult.
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Characteristics: feeding and increasing volume
Primitive nymph
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Apterygota: anamorphosis or epimorphosis
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More appendages at the sides of abdomen: flipping
organ
The same typical nymph
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Pterygota
Paurometamorphosis
Nymph and adult are different : wings and
reproductive organ
Nymph and adult are same: figure, internal and
external organs, as well as habit and habitation
atypical larva
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Larvae of complete metamorphosis
Larvae are different to adults in figure, internal and
external organs, as well as habit and habitation
Wings develop in the larva
No wings outside the larva
No compound eyes
Pupa stage
Types of atypical larva
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protopod larvae
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potypod larvae
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oligopod larvae
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apodous larvae
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Oligosegmented protopod larvae
Polysemented protopod larvae
campodeiform larvae
eruciform larva
carabiform larva
Scarabaeform larva
elateriform larva
platyform larvae
eucephalous larvae
hemicephalous larvae
acephalous larvae
Protopod larvae
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Parasitic hymenopteran insects
Little yolk
Thin chorion or no chorion
Larvae hatche at the early
stage of embryo development
Some larval insects do not segment in their abdomen
Thoracic legs are simple protuberance
Nervous and respiratory systems do not develop
Mouthparts are undergrown
Absorb host’s nutriment through their integument
Potypod larvae:
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Except for thoracic legs, the larvae have pairs of
abdominal legs
campodeiform larvae
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Campodeiform larvae have a flattened body with
long legs, usually with filaments on the end of the
abdomen.
Larvae of some Megaloptera, Neuroptera, and
Trichoptera are typical examples.
megaloptera larva
eruciform larva
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Eruciform larvae are cylindrical; they have a wellformed head, thoracic legs, and abdominal prolegs.
Larvae of Lepidoptera and sawflies are typical
examples.
Lepidopteran larva
oligopod larvae
 Coleoptera/ Trichoptera/ some of Neuroptera
 Thoracic legs are developed
 No abdominal legs
Carabiform larvae
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Carabiform larvae are similar to the campodeiform
type, but the legs are shorter and filaments are
lacking on the end of the body.
They receive their name from the larvae of carabid
beetles.
Chrysomelid beetle larvae are of the same type.
Scarabaeform larva
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Scarabaeiform larvae are C-shaped, have a
welldeveloped head, and usually possess thoracic legs
but lack prolegs.
The type is named after larvae of scarabaeid beetles
Larvae of sweetpotato weevil
Elateriform larvae
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Elateriform larvae are cylindrical, smooth, and
relatively tough-skinned larvae with short legs.
They are named after larvae of click beetles
Larvae in the beetle family Tenebrionidae also have
this appearance.
click
beetle
tenebrio molitor
Platyform larvae
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Platyform larvae are broad and flat with legs short or
absent.
This type is not common, but examples are found
among larvae of some syrphid flies, certain
caterpillars, and blister beetles.
syrphid flies
apodous larvae
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Devoid of legs and prolegs.
Vermiform larvae
Diptera /Anoplura/ some of Hymenoptera and
Coleoptera
Root Maggots
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eucephalous larvae
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hemicephalous larvae
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acephalous larvae
Pupation
It seems a still stage: Complete metamorphosis
 Prepupa
 Decomposition of old organs
 Generation of new organs
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Insect Pupae
Classes based on
whether the
appendages are
free or adhere to
the body.
Surface Anatomy of Pupa
(ventral view)
Types of insect Pupae
Pupal
Type
Common
Name
Description
Examples
Obtect
Chrysalis
Developing appendages (antennae,
wings, legs, etc.) held tightly
against the body by a shell-like
casing. Often found enclosed
within a silken cocoon.
Butterflies
and moths
Exarate
None
All developing appendages free
and visible externally
Beetles,
Lacewings
Body encased within the hard
exoskeleton of the next-to-last
larval instar
Flies
Coarctate Puparium
Obtect
Exarate
Coarctate
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Encased in hardened cuticle of next to last larval
instar – puparium
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Diptera
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This is the coarctate
type with the
puparium removed –
note pupa itself is
exarate
Protection of pupa
Main variation of pupal stage
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External variation: integument, antenna, eyes,
mouthparts, legs, wings and genital organs
Internal variation: histolysis and histogenesis
Emergence
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Definition
incomplete metamorphosis
complete metamorphosis
Monarch Butterfly emergence
Emergence
Sexual dimorphism
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Females and males are different: sex glands and
outside genital organs
Other different sides: Individual size, type of figure,
variation of coloration
Sexual dimorphism of
tumble beetle
Female
Male
Strepsiptera
Monarch butterfly
Monarch male
Monarch female
Polymorphism
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Individual size, type of figure, variation of coloration
are different in the same sex in one species.
Adults, eggs,
larvae, pupae.
Life of adults
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The last stage of insect.
Sex is ripe in this stage and the insects have
generative ability.
Flying ability and sensory apparatus are developed.
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The larval form of this moth (a) does not have
wings or eyes, two important adaptations that the
adult form (b) has.
replenish nutrient
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Some insects mate, blow and die soon after they
emergence
Most insects need replenish nutrient:
Orthoptera ,Hemiptera and other incomplete
metamorphosis insects
all the blood-absorb insects
Mating
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Sex pheromone
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Sound
Life history
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Generation : leave from mother’s body- generate
their own offspring.
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Voltism: generation numbers in one year.
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univoltine
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bivoltine
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polyvoltine
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partvoltine
Univoltine
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Univoltine cycles refers to insects with a single
generation each year – most of the population is at
the same growth stage at any one time.
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praying mantids,
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silk moth
Multivoltine cycles
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Multivoltine cycles refers to more than one
generation per year – more generations per year
means more overlap between generations
houseflies, thrips, aphids
Partvoltine
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The lifecycle takes more than one year to complete
•17 year Cicada takes 17 years to complete cycle
Dormancy
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Dormancy is a seasonally recurring period in the
insects lifecycle when growth development and
reproduction are suppressed.
– if it occurs in summer it is aestivation
– if it occurs in winter it is hibernation – most
common in temperate climates
Hibernation
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Many insects die when winter approaches.
But many others live through the cold by
hibernating in the egg, larval, or pupal stage.
A number of adult insects, including houseflies,
mosquitoes, ladybugs, and some moths and
butterflies, also hibernate.
They spend the winter in barns, cellars, attics,
caves, holes in trees, burrows in the ground, or
other protected places.
Diapause in Insects
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A genetically determined state of suppressed
development (cf. quiescence, an immediate
response to adverse weather)
Neurohormonally controlled, but can be triggered
by environmental cues
A strategy for withstanding adverse environmental
conditions (extreme cold, prolonged dry season)
Two types of diapause
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Obligate – genetically programmed, all individuals
in population enter diapause irrespective of
environment; univoltine species.
Facultative – ‘decision’ during a sensitive
developmental point, cued by the environment.
Most reliable environmental indicator for predicting
onset of winter is daylength (i.e. critical
photoperiod induces diapause). Bivoltine or
multivoline species.
Diapause can occur in any
lifestage, but is species-specific
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Egg: silkworm, red-backed cutworm; often maternally
determined, i.e. photoperiod to which adults are
exposed.
Long day – eggs will diapause; short day – no
diapause.
Larval: spruce budworm (2nd instar)
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Pupal: many lepidopterans (best studied), some
lacewings
Adult: diapause = delay in reproduction; e.g.
milkweed bug, allows dispersal of young adults;
results from a lack of JH (i.e. CA are inactive)
Alternation of generations
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Multivoltine sp. where succeeding generations are
different in mode of reproduction or morphology
are said to have alternating generations
Aphids: in a simple aphid life cycle:
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winter is spent in egg stage
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in spring all hatch as wingless females
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stem mothers reproduce parthenogenetically
and produce more females
by midsummer winged (alate) and wingless
females are produced – winged disperse
in late summer and fall winged males and
wingless females are produced
mating occurs in this sexual generation and
eggs are produced for overwintering
Aphid
Alternation of generations
Habits and behavior
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Habits : species or population
Behavior : sense and reaction---insect ethology
Biological clockinsect clock
 Diurnal insect
 Nocturnal insect
 Crepuscular insect
Feeding habits
According to food nature:
 phytophagous / herbivorous
 sarcophagous / carnivorous
 saprophagous
 omnivorous
Herbivorous
carnivorous
Feeding habits
according to the food spectrum
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Polyphagous : many species of different families
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Ologophagous:some species of one family
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monophagous:only one species
 An orientated movement of an organism.
Insect taxis
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Act of orienting towards some external stimulus or
combination of stimuli.
Spatial orientation, aided by different sensory
modalities, is described by the corresponding term
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light (phototaxis)
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smell (chemotaxis)
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sound (phonotaxis)
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gravity (geotaxis)
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If orientation is towards the source, it is called a
positive taxis, and away from the source a negative
taxis.
In such instances individuals move in a directed
fashion along a particular stimulus gradient until
they reach a perceived optimal range.
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Mosquitoes are
attracted by
perspiration, warmth,
body odor, carbon
dioxide, and light.
Humans vary in their
body chemistry and
this is why some
people are more prone
to being bitten than
others
Insect Mimicry
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Katydids mimicry to a wide variety of environments. Can you
find the katydid in each picture?
Insect Mimicry
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Mimicry = Resemblance of an organism (the mimic)
in color, pattern, form, behavior, or a combination of
these to another organism or object (the model).
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The taking on by an animal of the look of another
sort of animal or thing for the purpose of:
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keeping itself safe (traditional sense)
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enhancing predation
Three components:
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Model - species or object being mimicked.
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Mimic - looks and acts like another species or
object by resembling the models
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Dupe- the deceived predator or prey.
Kinds of Mimicry
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Aggressive mimicry
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Müllerian mimicry
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Batesian mimicry
Aggressive mimicry
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The development of an appearance of things
around it that keeps the mimic from being seen by
prey animals.
Aggressive mimics resemble the background or
signals that it is something else to aid in capturing
prey.
Goal of aggressive mimicry is to enhance predation;
not to avoid being eaten
examples:
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Malaysian preying mantids
Resemble flowers.
Pollinating insects come to the flowers.
Captured and consumed.
Female fireflies of the genus Photuris
Photuris females mimic the signal of other firefly
species.
Responding male firefly is captured and eaten.
Müllerian mimicry
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Unrelated species that are distasteful or otherwise
protected come to resemble each other.
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All are mimics and all are models.
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Müllerian mimics advertise their dangerousness by:
APO somatic (warning) coloration
Sound - buzzing
Behavior - aggressive flight
Examples
Lady beetles
Honey bees and drone bees (automimicry)
Batesian mimicry
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A harmless mimic resembles an unpalatable,
dangerous, or otherwise protected model.
False advertising:
Auditory mimicry
fly wing-beat sound which is very much like the
buzzing of a bee
Visual mimicry - mimic the color and shape of bees
Behavioral mimicry - aggressive flight behavior
Example: Monarch Butterfly - a distasteful model for
the harmless Viceroy butterfly
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Hawk Moth Mimicry
This moth caterpillar defends itself by mimicing a
snake.
Insect mimicry
Caterpillars that Match Their
Environments
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Caterpillars of
the moth
Nemoria
arizonaria differ
in shape
depending on
their diet.
Caterpillars that
hatch in the
spring resemble
the oak flowers
on which they
Caterpillars that Match Their
Environments
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Caterpillars that hatch
in the summer eat
leaves and resemble
oak twigs.
Experiments have
demonstrated that
chemicals in the leaves
control the switch that
determines whether
caterpillars will mimic
flowers or twigs.
Protective coloration
Protective Coloration in Insects
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Insects are not always able to defend themselves,
and so many of them have developed ways for
blending into their surroundings.
Some insects hide in plain sight, their bodies
resembling non- living or inedible objects such as
bark, thorns, buds, twigs, leaves, or bird droppings.
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That's right, the caterpillar of the viceroy butterfly
looks just like a bird dropping and easily gets
passed up by an animal looking for a meal.
Other insects, such as the stick insects are shaped
like twigs or leaves.
stick insect
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The dead-leaf butterfly of India is also another
example of this type of protective coloration and
camouflage.
When they fold their wings over the back, the
undersides of the wings look just like dead leaves complete with stem, leaf veins, and shiny spots that
look like holes nibbled by leaf-feeding insects.
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Many night-flying moths are colored and marked so
that they "disappear" when they sit on a rock or
tree trunk during the daylight hours.
Some insects create a disguise for themselves by
covering their bodies with plant parts, stones, dirt,
cast skins, and other inedible "junk".
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Insects may have another reason to use
camouflage: to improve their chances for sneaking
up on their prey.
For example, some mantids are shaped and/or
colored like flower petals or leaves and go
unnoticed by plant-inhabiting insects.
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Some insects are brightly colored and can't help but
be noticed by other animals.
These insects are also using their coloration as
protection, but in a very different way.
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Some insects (such as orange-and-black monarch
butterflies and milkweed bugs and red-and-black
ladybird beetles and milkweed beetles) are using
their bright colors to warn other animals that they
are distasteful and should not be eaten.
Other insects (such as black-and-yellow bees and
wasps) are telling other animals to stay away
because they can defend themselves by stinging.
Warning color
Aggregation
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many numbers of one species aggregate in one place
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Temporary : potato ladybird
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Permanent : flying grasshopper
Why Insects Aggregate:
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environmental conditions
aggregation as a mating strategy
aggregation as a defensive strategy
chemical cues in aggregation
Black Slug Cup Moth
Scientific Name: Doratifera casta
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The caterpillars of this
species feed
communally and
aggregate on the leaf
surface.
Once the surface layer
of the leaf has been
consumed, the
caterpillars spread out
onto other leaves,
each inhabiting a
single leaf.
Ladybirds- hibernation or mating
Aphids
Aggregation
termite ( a social insect)
Migration
Active travel between distant locations.
Introduction to Movement
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One of the most prevalent features of insects;
Earth is canned by millions of insects flying on air
currents, who encounter suitable and unsuitable
habitats
Understanding movement critical for characterizing
population dynamics
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Types
a) emigration - movement out of an area
b) immigration - movement into an area
Movement is sometimes more important than
natality or mortality
Normal behavioral/physiological movements often
modified by weather
Can result in substantial mortality (e.g., over water,
glaciers, etc.)
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The most common insects that migrate are Monarch
(Danaus plexippus) butterflies.
Every fall, North American monarch butterflies
gather in great clouds and fly south to spend the
winter in tropical or subtropical areas.
That is a distance of over 3,000 kilometres!
In spring, they drift northward again, laying eggs as
they go.
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Their offspring, after becoming adults, continue the
northward journey.
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Painted ladies and several other species of
butterflies also migrate with the seasons, as do
some species of moths.
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Many other insects also make long migratory flights.
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The most famous are probably the locusts.
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They often travel in swarms so huge that they black
out the sun.
Scientists do not know why locusts migrate, except
that they do so after building up an enormous
population.
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Locusts do not migrate because they are hungry.
In fact, they may leave a land of plenty and not
stop to feed during most of their long flight.
But after they settle down, they destroy every bit of
plant life.
Biological and Ecological
Significance of Migration
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Important Adaptive Characteristic
Use wind flow to relocate and colonize favorable
habitats
Dispersal mechanism
Transport insects beyond the boundaries of their old
reproductive site
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Strongly Influences Population Dynamics
Migrations often responsible for tremendous
outbreaks
May change genetic makeup of population
Prevalence
As research continues, more insects are added to
the migrant list
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Evolutionary Aspects
Two-way migrants (obvious advantages, habitat
exploitation)
What about one-way migrants?
a) if no remigration, then genetic dead end
b) remigration is not well understood (may be
more common)
c) migration may facilitate incremental habitat
gains
Dispersal
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Travel of Individuals, which (1) as an ecological
process affects distribution of individuals; (2) as a
genetic process affecting geographic differentiation
and variation.
Adaption