The science that deals with insect’s individual
It is divided into the study of reproduction,
embryology and adult
Larval stage or nymph stage
Stage: hatching from egg to the adult.
Characteristics: feeding and increasing volume
Apterygota: anamorphosis or epimorphosis
More appendages at the sides of abdomen: flipping
The same typical nymph
Nymph and adult are different : wings and
Nymph and adult are same: figure, internal and
external organs, as well as habit and habitation
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
Types of atypical larva
Oligosegmented protopod larvae
Polysemented protopod larvae
Parasitic hymenopteran insects
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
Except for thoracic legs, the larvae have pairs of
Campodeiform larvae have a flattened body with
long legs, usually with filaments on the end of the
Larvae of some Megaloptera, Neuroptera, and
Trichoptera are typical examples.
Eruciform larvae are cylindrical; they have a wellformed head, thoracic legs, and abdominal prolegs.
Larvae of Lepidoptera and sawflies are typical
Coleoptera/ Trichoptera/ some of Neuroptera
Thoracic legs are developed
No abdominal legs
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
Chrysomelid beetle larvae are of the same type.
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 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
Platyform larvae are broad and flat with legs short or
This type is not common, but examples are found
among larvae of some syrphid flies, certain
caterpillars, and blister beetles.
Devoid of legs and prolegs.
Diptera /Anoplura/ some of Hymenoptera and
It seems a still stage: Complete metamorphosis
Decomposition of old organs
Generation of new organs
Classes based on
free or adhere to
Surface Anatomy of Pupa
Types of insect Pupae
Developing appendages (antennae,
wings, legs, etc.) held tightly
against the body by a shell-like
casing. Often found enclosed
within a silken cocoon.
All developing appendages free
and visible externally
Body encased within the hard
exoskeleton of the next-to-last
Encased in hardened cuticle of next to last larval
instar – puparium
This is the coarctate
type with the
puparium removed –
note pupa itself is
Protection of pupa
Main variation of pupal stage
External variation: integument, antenna, eyes,
mouthparts, legs, wings and genital organs
Internal variation: histolysis and histogenesis
Monarch Butterfly emergence
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
Individual size, type of figure, variation of coloration
are different in the same sex in one species.
Life of adults
The last stage of insect.
Sex is ripe in this stage and the insects have
Flying ability and sensory apparatus are developed.
The larval form of this moth (a) does not have
wings or eyes, two important adaptations that the
adult form (b) has.
Some insects mate, blow and die soon after they
Most insects need replenish nutrient：
Orthoptera ,Hemiptera and other incomplete
all the blood-absorb insects
Generation : leave from mother’s body- generate
their own offspring.
Voltism: generation numbers in one year.
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.
Multivoltine cycles refers to more than one
generation per year – more generations per year
means more overlap between generations
houseflies, thrips, aphids
The lifecycle takes more than one year to complete
•17 year Cicada takes 17 years to complete cycle
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
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
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
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
Diapause can occur in any
lifestage, but is species-specific
Egg: silkworm, red-backed cutworm; often maternally
determined, i.e. photoperiod to which adults are
Long day – eggs will diapause; short day – no
Larval: spruce budworm (2nd instar)
Pupal: many lepidopterans (best studied), some
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
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:
winter is spent in egg stage
in spring all hatch as wingless females
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
Alternation of generations
Habits and behavior
Habits : species or population
Behavior : sense and reaction---insect ethology
Biological clockinsect clock
According to food nature：
phytophagous / herbivorous
sarcophagous / carnivorous
according to the food spectrum
Polyphagous : many species of different families
Ologophagous：some species of one family
monophagous：only one species
An orientated movement of an organism.
Act of orienting towards some external stimulus or
combination of stimuli.
Spatial orientation, aided by different sensory
modalities, is described by the corresponding term
If orientation is towards the source, it is called a
positive taxis, and away from the source a negative
In such instances individuals move in a directed
fashion along a particular stimulus gradient until
they reach a perceived optimal range.
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
Katydids mimicry to a wide variety of environments. Can you
find the katydid in each picture?
Mimicry = Resemblance of an organism (the mimic)
in color, pattern, form, behavior, or a combination of
these to another organism or object (the model).
The taking on by an animal of the look of another
sort of animal or thing for the purpose of:
keeping itself safe (traditional sense)
Model - species or object being mimicked.
Mimic - looks and acts like another species or
object by resembling the models
Dupe- the deceived predator or prey.
Kinds of Mimicry
The development of an appearance of things
around it that keeps the mimic from being seen by
Aggressive mimics resemble the background or
signals that it is something else to aid in capturing
Goal of aggressive mimicry is to enhance predation;
not to avoid being eaten
Malaysian preying mantids
Pollinating insects come to the flowers.
Captured and consumed.
Female fireflies of the genus Photuris
Photuris females mimic the signal of other firefly
Responding male firefly is captured and eaten.
Unrelated species that are distasteful or otherwise
protected come to resemble each other.
All are mimics and all are models.
Müllerian mimics advertise their dangerousness by:
APO somatic (warning) coloration
Sound - buzzing
Behavior - aggressive flight
Honey bees and drone bees (automimicry)
A harmless mimic resembles an unpalatable,
dangerous, or otherwise protected model.
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
Hawk Moth Mimicry
This moth caterpillar defends itself by mimicing a
Caterpillars that Match Their
hatch in the
the oak flowers
on which they
Caterpillars that Match Their
Caterpillars that hatch
in the summer eat
leaves and resemble
chemicals in the leaves
control the switch that
caterpillars will mimic
flowers or twigs.
Protective Coloration in Insects
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.
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.
The dead-leaf butterfly of India is also another
example of this type of protective coloration and
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.
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".
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.
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.
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.
many numbers of one species aggregate in one place
Temporary : potato ladybird
Permanent : flying grasshopper
Why Insects Aggregate:
aggregation as a mating strategy
aggregation as a defensive strategy
chemical cues in aggregation
Black Slug Cup Moth
Scientific Name: Doratifera casta
The caterpillars of this
aggregate on the leaf
Once the surface layer
of the leaf has been
caterpillars spread out
onto other leaves,
each inhabiting a
Ladybirds- hibernation or mating
termite ( a social insect)
Active travel between distant locations.
Introduction to Movement
One of the most prevalent features of insects;
Earth is canned by millions of insects flying on air
currents, who encounter suitable and unsuitable
Understanding movement critical for characterizing
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,
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
Their offspring, after becoming adults, continue the
Painted ladies and several other species of
butterflies also migrate with the seasons, as do
some species of moths.
Many other insects also make long migratory flights.
The most famous are probably the locusts.
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
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
Biological and Ecological
Significance of Migration
Important Adaptive Characteristic
Use wind flow to relocate and colonize favorable
Transport insects beyond the boundaries of their old
Strongly Influences Population Dynamics
Migrations often responsible for tremendous
May change genetic makeup of population
As research continues, more insects are added to
the migrant list
Two-way migrants (obvious advantages, habitat
What about one-way migrants?
a) if no remigration, then genetic dead end
b) remigration is not well understood (may be
c) migration may facilitate incremental habitat
Travel of Individuals, which (1) as an ecological
process affects distribution of individuals; (2) as a
genetic process affecting geographic differentiation