Transcript Slide 1 - Images

INSECTS!
1. Insects belong to
– Kingdom Animalia
– Phylum Arthropoda
– Subphylum Uniramia
– Class Insecta
• 2. Insect bodies are divided
into 3 main parts; head,
thorax, abdomen.
• 3. Insects have mandibles and
one pair of antennae, three
pairs of legs, and usually two
pairs of wings.
The abdomen is composed of 9
– 11 segments.
4. The study of insects is
called entomology. Insects are
classified into 30 orders
based on characteristics such
as mouthparts, number of
wings, and type of
development.
5. Some entomologist believe
there may be as many as 10
million species of insects. Why
are they so successful?
– They can fly to catch prey
or escape from other
animals.
– They have a light but strong
exoskeleton.
– They are small so several
are able to live in different
local environments without
competing for resources and
food.
– They have short life spans
and produce large number of
eggs so natural selection
occurs more quickly.
6. A look at the grasshopper!
• External Structure
– The body is divided into 3
tagmata (body parts). The
head contains the
mouthparts, a pair of
unbranched antennaem,
simple and compound eyes.
• The thorax is divided into 3
parts. The first is the
prothorax. It attaches to the
head and has the first pair of
legs.
• Next is the mesothorax. It
has the forewings and the
second pair of legs.
• The last is the metathorax.
It attaches to the abdomen
and has the hindwings and
large jumping legs. These have
spines and hooks used for
attachment.
• They have a pair of leathery
forewings which cover the
membranous hindwings when it
is not flying. The hindwings
are powered by muscles that
are attached to the inside of
the exoskeleton.
• The segments in the last
tagmata (the abdomen) are
composed of upper and lower
plates joined together by a
flexible sheet of exoskeleton.
• Feeding and Digestion
• They are herbivores with
mouthparts modified for
cutting and chewing leaves and
grass. The upper lip is called
the labrum, the lower lip is
called the labium.
• They hold the food while the
mandibles tear off pieces.
Behind the mandibles are the
maxillae which also help hold
and cut the food.
• Insect mouthparts are
adapted to each ones food
source. Mosquitoes have thin,
long mouthparts made into a
tube. Fly mouthparts are like
sponges to soak up liquids.
• Food enters the mouth and is
moistened by the salivary
glands. It then passes through
the esophagus into the crop
where it is stored
temporarily.
• From the crop it passes into
the gizzard where it is
shredded. The shredded food
then enters the midgut where
it is soaked with enzymes
secreted from the gastic
ceca.
• Nutrients are absorbed
through the walls of the
intestine into the body while
the wastes are moved through
hindgut and out the anus.
• Circulation, Respiration, and
Excretion!
– Insects have an open
circulatory system. Their
blood is called hemolymph
and is moved around by a
heart in the thorax and
abdomen.
• They use a system of trachea
that exchange oxygen and
carbon dioxide.
• They use Malpighian tubules to
collect water and cellular
wastes from the hemolymph.
For insects that live in dry
environments this helps
conserve water.
• Nervous System
• The nervous system consists
of a brain and a ventral nerve
cord with ganglia located in
each body segment. Nerves
extend from the brain to the
antennae, eyes, and other
sensory organs.
• They have simple eyes that
can detect changes in light
intensity and compound eyes
that can form images and
detect movement.
• They have a sound sensing
organ called a tympanum. It is
a large oval membrane that
covers an air-filled cavity on
each side of the abdomen.
Sound wave cause it to
vibrate. These vibrations are
detected by nerve cells inside
the cavity.
• They also have sensory hairs
located over the body. At the
base of each hair is a nerve
that can detect movement
made by wind, vibration, etc.
• Reproduction!
• All insects have separate
sexes. During mating the male
deposits the sperm into the
females seminal recepticle
where they are stored until
the eggs are released from
the ovaries.
• After the eggs are released
they are fertilized internally.
• The last segment of the
females abdomen has an organ
called an ovipositor. She uses
this to dig a hole in the soil
where she lays her fertilized
eggs.
7. Insect Development
• Almost all insects undergo
some type of body change
within their lifetime. This
developmental change in form
is called metamorphosis.
There are two main types of
metamorphosis; complete and
incomplete.
• In incomplete metamorphosis a
nymph hatches from an egg
and gradually develops into an
adult.
• A nymph is an immature form
of an insect that looks
somewhat like an adult but is
smaller and has un-developed
wings and reproductive organs.
The nymph molts several times
until adult form is reached.
• Examples of insects that
undergo incomplete
metamorphosis are
grasshoppers, mayflies,
dragonflies, and termites.
• In complete metamorphosis an
insect undergoes two stages of
development between the egg
and adult. In both stages it
looks nothing like the adult
form.
• Ex. Butterflies.
• A wormlike larva (caterpillar)
hatches from an egg.
Caterpillars have three pair of
jointed legs on the thorax and
lots of unsegmented legs on
the abdomen. These are
vegetarians and can cause
major damage.
• The larva molts several times
as it grows. In the last larval
stage it finds a spot on a
branch and hangs upside down.
The exoskeleton splits and
falls off revealing the pupa
stage.
• A pupa is a stage of
development in which an insect
changes from a larva to an
adult. The pupa of butterflies
are encased in a chrysalis,
moths are in a cocoon, and
flies are in a puparium.
• Inside the pupa the larval
tissue breaks down and
transformation into adult form
begins. When metamorphosis
is complete a fully developed
adult emerges.
• Insects that undergo complete
metamorphosis include
butterflies, moths, beetles,
mosquitoes, bees, flies, and
most insects.
8. Importance of
metamorphosis.
It helps reduce competition
between the adult and larval
stages for resources such as
food and space.
• It also helps insects survive
harsh weather conditions.
Most butterflies and moth
spend the winter encased in
the protective chrysalis or
cocoon.
• Defense
• Insects have developed several
passive and aggressive
defenses to help them survive.
• One form of passive defense
is camouflage which helps
them hide. They may look like
sticks or leaves.
• Some have venomous stingers
like bees and wasps.
• Some use chemical warfare.
The bombardier beetle
defends itself by spraying a
hot stream of noxious
chemicals through an opening
in its abdomen which it can
aim at a target.
• Insects that defend
themselves by being poisonous
or by tasting bad often have
bold, bight, color patterns
that serve as warnings.
• This is called warning
coloration. Ex. bees and
wasps often use yellow and
black.
• Mullerian mimicry is when one
dangerous species mimics the
warning coloration of another
dangerous species. Ex bees
and wasps.
• Batesian mimicry is when a
harmless species looks like a
dangerous one to encourage
predators to avoid it.
• Insect behavior Most insect behavior is innate.
These are genetically
programmed. They are known
without any experience.
• Social insects live in colonies.
Members of the colony have
different responsibilities. This
is highly evolved in bees,
wasps, ants, and termites.
• Each kind of individual in a
colony is called a caste.
Usually 3 or 4 castes are
present.
• Reproductive females are
called queens.
• Workers may be sterile males
or females. They support and
defend the colony.
• Reproductive males are called
drones.
• Soldiers are sterile males with
large mandibles for defense
and attack.
• Insects and Humans
• Insect pollination of crops is
worth 19 billion dollars in the
U.S.
• They are used as biological
control agents by feeding on
or destroying harmful
substances.
• In the soil they help in
decomposition, aeration, and
soil formation.
• Important part of the food
web.
Many are parasites and spread
diseases such as malaria,
yellow fever, bubonic plague,
encephalitis, and typhus.
• They can destroy crops and
spread plant diseases such as
Dutch elm disease and potato
viruses. Crop damage due to
insects in the U.S. is
estimated to be 5 billion
dollars annually.
• Order Archaeognatha
• Bristletails are wingless
insects that hide under bark,
in litter, and in rock crevices.
They feed on algae, lichens,
and plant debris.
• Order Zygentoma - Silverfish
and firebrats often live in
people's houses, but are also
found in habitats such as
caves and nests of other
animals, including ant colonies.
• Order Ephemeroptera Mayflies are an ancient
lineage of winged insects.
Adult mayflies live only for a
few hours, but nymphs live
under water in ponds and
streams for a long time.
• Order Odonata • Dragonflies and damselflies
are charismatic insects that
have captured the imagination
of naturalists and artists
across cultures. Juveniles are
voracious underwater
predators, while the winged
adults are fierce aerial
hunters.
• Order Grylloblattodea - Rock
crawlers are extremophilic
insects that thrive in nearfreezing temperatures.
• Order Dermaptera - Earwigs
have a pair of forceps-like
cerci at the tip of their
abdomen. They are used to
open the wings, to capture
prey, and for defense.
• Order Embioptera Webspinners use silk glands on
their enlarged forelimbs to
weave silk tunnels and
chambers on rocks, the bark
of trees, or in leaf litter.
Order Phasmida - Stick Insects
are large, slow-moving insects
that resemble sticks or leaves.
• Order Orthoptera -includes
familiar insects like
grasshoppers, locusts,
crickets, and katydids. The
members of this group are
readily identified by their
strong hind legs which are
modified for jumping.
• Order Hemiptera - a diverse
order of hemimetabolous
insects. Members of this
group are characterized by
unique mouthparts modified to
form an articulated beak
(rostrum) for piercing and
sucking liquid food.
Order Blattodea - Cockroaches
are mostly nocturnal insect,
with biting mouthparts and legs
that are adapted for swift
running. flattened, allowing the
animals to hide in narrow
spaces, for example under bark
or in crevices of trees and
rocks.
Order Mantodea - Mantids are
ferocious predators. Insects
form their primary prey, but
large mantids have been known
to capture and consume small
scorpions, lizards, frogs, birds,
snakes, fish, and even rodents.
Order Coleoptera - The most
unusual property of beetles is
not some aspect of their
structure or natural history,
but their sheer number. There
are more known species of
Coleoptera than any other group
of organisms, with over
350,000 described species.
Order Siphonaptera - Fleas are
ectoparasites of mammals and
birds. Both males and females
use piercing-sucking mouthparts
to feed on the blood of their
host. Some species are vectors
of human disease including
plague (Yersinia pestis).
Order Diptera - Flies are
minute to small, soft-bodied
insects with sucking mouthparts
and only one pair of functional
wings.
• Order Lepidoptera - The
butterflies, moths, and
skippers. For most species,
the majority of the life cycle
is spent in the larval
(caterpillar) stage.
• Order Hymenoptera - include
insects like wasps, bees, ants,
bumblebees, and sawflies.
Hymenoptera are of economic
significance as pollinators,
agents of biological control of
other insects, and household
and forest pests.