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OBJECTIVES OF BASIC ENTOMOLOGY
At the end of this section students should be able to:
1) Understand that due to the great diversity of insects, and their genetic
flexibility, here will always be species causing damage to forests
and forest products.
2) Know the major taxonomic divisions including phylum, class, order,
family, genus and species.
3) Know the characteristics of the phylum Arthropoda and the differences
between the Chelicerata and Mandibulata.
4) Describe the specialized features of the class Insecta.
5) Describe the generalized parts of the chewing mouthparts and be
familiar with the more specialized mouthpart types found
throughout the class Insecta.
6) Describe the internal morphology of insects particularly the features of
the digestive, respiratory, circulatory, excretory, reproductive and
nervous systems.
7) Describe the various types of metamorphosis and give examples of
insect groups that have those types of development.
8) Define the terms instar, stadium, and generation in terms of insects.
9) Know the common and order names of the insect groups discussed in
class and in the textbook.
Basic Entomology
INSECTA
Is a Taxonomic CLASS in the
Phylum
ARTHROPODA
The Taxonomic Hierarchy is:
Kingdom ----- Animal
Phylum ----- Arthropoda
Class ----- Insecta
Order ----- Coleoptera
Family
Genus
Species
All Arthropods Have Several
Common Structural Characteristics:
1)A chitinous exoskeleton
The suit of armor of
this knight is somewhat
analogous to the insect
exoskeleton
All arthropods have:
2) Bilateral Symmetry
All arthropods have:
3) Jointed Appendages
All arthropods
have:
4) Segmented Bodies
All arthropods also have:
•A tubular digestive tract
•A dorsal tubular circulatory system
•A ventral nervous system
The Phylum Arthropoda Includes:
Chelicerata
= mouthparts outside the head
Mandibulata
= mouthparts inside the head
Chelicerata include some members
important to foresters, including
Scorpions, spiders, and ticks.
Class Arachnida
Characteristics of Chelicerata include:
•All those of general arthropods
and
•2 body regions
•No antennae
•4 pair of walking legs
Mandibulata include:
Lobsters – Class Crustacea
Centipedes –
Class Chilopoda
Millipedes – Class Diplopoda
Mandibulata also include:
The Class Insecta:
Insects within the Class Insecta
have all the characteristics
of Arthropods
and
•3 body regions
Head Thorax Abdomen
Insects also have:
•3 pairs of legs
(not two in spite of what you
may see in some movies)
•1 pair of antennae
The other Classes (Dipoloda, Chilopda)
of Arthropods do not have these last
three characteristics.
So, spiders are arthropods because
they have:
1) Segmented bodies
2) Jointed appendages
3) Bilateral symmetry
4) A chitinous exoskeleton
But spiders are not insects because
they have:
1) Only two body regions (not three)
2) 4 pairs of legs (not 3)
3) No antennae
Knowing what
you now know
about
Arthropods;
What is
wrong with
this cartoon?
Characteristics of exoskeleton and
endoskeleton. Exoskeleton provides:
1) Support
Large churches
such as they
have at the Air
Force Academy
have an external
supporting
structure, or
exoskeleton
which allows
for large open
spaces.
Exoskeleton provides: 2) Muscle attachment
Insect
muscles are
attached to
the interior
of the
exoskeleton
Exoskeleton provides:
3) Body covering & good protection
Exoskeleton provides:
4) Water conservation.
Like the
cactus, insects
must conserve
water
Exoskeleton provides:
5) Growth restrictions, which is a
problem.
Cicada
Nymph
just before
molting
Exoskeleton provides:
6) Good mechanical advantage
For Example:
A common ordinary flea can jump
about 8 inches high.
A comparable feat
for a human would
be a leap of 800 feet.
All Insecta have 3 body regions which are
called Tagma
Tagma are groups of segments that function
together to perform a general task.
•Head = perception, food intake
•Thorax = locomotion, food processing
•Abdomen = reproduction, excretion
Structures on the Head include:
1) Antenna
2) Eyes
3) Mouthparts
1) Antenna
• These are the odor receptors of insects
• They come in a variety of forms and
shapes
• They are used by entomologists in
insect identification
Filiform Antennae, crickets et al.
Lamellate Antenna – May or June Beetles
Feathery Antennae: moths, butterflies
Aristate Antennae of TseTse Fly
Genulate or “elbowed” Antenna: Ants
The Velvet Ant is
not an ant! Note
the antennae.
It is a wasp and
also called a
Cow Killer.
Plumose antennae of Male Mosquitoes
2) Eyes
• Compound Eyes
• Simple eyes called Ocelli
Compound eyes
Compound eyes are composed of many
individual eye units called Ommatidia
Simple eyes - composed of 1 unit, often
arranged in the shape of a triangle on
adult insects
Larval insects, like
caterpillars, do not
have compound eyes.
But they may have
numerous Ocelli with
which they see
reasonably well.
3) Mouthparts: Insects have much variation in
mouthparts, depending upon food habits
and include:
•
•
•
•
Chewing -- grasshoppers, beetles, Lepidoptera larvae,
Chewing-lapping -- bees
Siphoning -- Butterflies
Piercing-Sucking -- aphids, mosquitoes, scale
insects, leafhoppers
• Sponging -- house flies
• Cutting-Sponging -- Deer flies, horse flies
Chewing Mouthparts – Lady bug
•Chewing-Lapping Mouthparts
Some insects, like honey bees, have normal
mandibles but other structures are modified into
sucking lapping devices.
Honeybees use their sucking mouthparts to collect nectar
and their chewing mouthparts to chew and create waxy
combs to store their nectar (honey).
•Siphoning Mouthparts
Butterflies and moths have mouthparts
permanently modified into a siphoning
tube
proboscus
Siphoning
mouthparts
are usually
coiled beneath
the head when
not in use
Lepidoptera mouthparts video
•Piercing-Sucking Mouthparts
Mosquitoes, aphids, seed bugs
•Sponging Mouthparts
Some insects, like house flies, have
mouthparts modified to “sponge
up” liquids
They can’t bite!
Sponging mouthpart video clip
•Cutting-Sponging Mouthparts
Horse flies and Deer flies cut a deep wound
then lap up the flowing blood
The Thorax consists of three segments:
1) Prothorax
2) Mesothorax
3) Metathorax
Legs are found on all three (promeso- & meta-) thoracic segments.
Wings, if they occur, are found on
the Mesothorax and Metathorax
(never on the Prothorax).
Prothorax = no wings
But has 1 pair legs
Mesothorax = wings &
1 pair legs
Metathorax = wings &
1 pair legs
1) LEGS
Leg segments include:
•
•
•
•
•
Coxa -- attached to body
Femur -- largest segment of leg
Tibia
Tarsus
Tarsal claws
Coxa
Femur
Tibia
Tarsal
segments
Tarsal
claws
The structure of legs of insects vary
depending upon use, but all have the
same basic parts. Some different leg types
include:
•Running
•Jumping
•Grasping
•Digging
•Clinging
•Swimming
Cursorial = Running legs can be found on fast
moving insects, like cockroaches
Sartorial = Jumping leg of grass hopper
Raptorial Leg of Praying Mantis. Designed
to grab and hold prey.
Fossorial =Digging leg of mole cricket
Sucking Louse with Clinging legs
Natatorial = Swimming
2)WINGS
There are various modifications of insect
wings, some with special functions.
These include:
•
•
•
•
•
Membrane Wings
Scale Wings
Haltares
Elytra
Hemi-elytra
Membrane
Wings
Haltare
Hind wings
of true flies
are greatly
reduced and
function as
balancing
organs called
Haltares
Scale Wings
Front wings of beetles consist of
hard protective covers (elytra)
True bugs (Hemiptera) have half of the
wing stiff and colorful.
The other half is membraneous.
These are called “hemi elytra”.
Most insect wings have “veins”.
Wing veins have several functions:
•Carry Blood (for a short time)
•Add Strength (exoskeletal)
•Add Strength (alter shape)
•Great taxonomic value
Abdomen
The functions of the abdomen are
•Reproduction
•Excretion
Abdomen
Appendages of the abdomen are
of two types:
•Reproductive appendages such as
genitalia or ovipositors
•Those not associated with
reproduction
Non-reproductive appendages: Cerci
Cerci on this male earwig
are used for defense
Tail-like
appendages on
mayflies are also
cerci
Reproductive Organ: Aedeagus
Females:
•Ovipositor – is the
egg laying device.
Insect ovipositors vary
greatly depending
upon where the eggs
are placed.
Walking sticks
deposit eggs
almost anywhere
and do not have a
specialized
ovipositor
Giant Ichneumonid
Some wood wasps place eggs deep in the wood.
They have very well developed ovipositors.
Ovipositor 5 inches long
Some insects have the ovipositor
modified as a defensive weapon.
The stinger of honey bees is a modified
ovipositor.
Honey bee
pulling away
from sting
End of
Basic Entomology
Part I