For 2nd year biology
Dr. Zeinab Abu-Elnaga
•Entomology 2014 firstname.lastname@example.org
Zoology Department, Faculty of Science http://zaboelnaga.synthasite.com
o General introductory lecture.
o External body morphology of insects and its
The head capsule
1. The antennae
2. The mouth parts
1. The wings
2. The legs
1. The cerci
2. The genitalia
3. The styli
4. Stinging apparatus
5. Springing apparatus
Insects are members of one of the biggest classes of the….. Phylum:
Arthropoda (Nonchordata with jointed legs)
Class: Insecta (Hexapoda) (i.e. =six-legged or possess 3 pairs of legs) .
A- Characters common between insects and other arthropods:
Triploblastic coelomate with bilateral symmetry
Segmented body and jointed appendages.
Locomotory system with skeletal muscles.
3 pairs of peristomal appendages.
Sense organs, Antennae (tactile & olfactory) & compound eyes.
Mostly Dioeceous (sexes separate)
Heamolymph (corresponding to both blood &lymph of vertebrates).
Blood circulation is open type.
Undergo metamorphosis (post-emberonic development).
B- distinguish characters for insects:
Three regions body (head [cephalization], thorax, & abdomen).
Only one pair of antenna, no antennules.
Sessile compound eyes, (stalked in Arthropods).
Peristomal appendages (mouth parts).
Thorax (pro-, meso-, & metathorax), each one with pair of legs.
Wings (meso- & metathorax).
Adults have no abdominal legs.
The space between the viscera is filled by fat tissue.
Tracheal system is well developed, and gills, but no lung books.
Excretion via malpighian tubules.
Size & shape
Advanced locomotory organs
The mouth parts
Central nervous system
The reproductive capacity
The digestive system
The fat tissue
Protection of quiescent stages
Periodicity of activity
Hibernation & diapause
Mimicry & protective coloration
Diversity of diet
Modes of reproduction
Life cycle duration
ECONOMIC IMPOTENCE OF INSECTS
Blood sucking insects (mostly
temporary ecto-parasites on
man or permanent ecto-
Myasis to man & animals
Spoils our food & drink.
damage of cloths & furniture
Caused by insects which
infest crop plants & beneficial
Plant pests: locusts, larvae of
many moths, thrips, fruit
Animal pests: warble flies
attack sheep & cattle, causing
decreased efficacy, milk, &
ECONOMIC IMPOTENCE OF INSECTS
Source of useful materials as
food, (bees, Aphids “honey
dew”, fried locusts, eggs of
big insects,…….. ect.)
clothing (salivary secretions
of silk worms)
Industry useful (natural dyes
Improvement of soil properties
Source of food for birds &
fishes, used, in turn food for
Discovery of juvenile hormone.
Some of them used as
biological control agents.
B- Benefits of insects
THE HEAD REGION & ITS APPENDAGES
o Insects have a distinct and well developed head
region = Cephalization.
o unsegmented, but it actually consists of a number
of fused segments.
THE HEAD CAPSULE
Corresponds to the cranium of vertebrates.
The typical structure evident in locusts & cockroaches.
POSITIONS OF THE HEAD
Pro-gnathous: head extended
longitudinally with body axis
(m.p are pointed forward,
perpendicular to longitudinal
body axis (m.p pointed
Opitho-gnathous: head bent
underneath thorax during rest
(m.p pointed backwards, Aphids)
Difintion: pair of jointed segments on front region of insects, mostly located
within socket, & its surface carries numerous fine hairs.
Function: tactile & olfactory organs (touch & smell respectively),moreover,
in mosquito it was for hearing (auditory).
Typical structure: three main regions:
1. Scape: basal part articulates with head capsule, contains one
segment almost, cylindrical in shape & movable in all directions.
2. Pedicel: short piece, connected to scape via memberanous narrow
ring, for bending.
3. Flagellum: long estpart, many sub-segments, flexible, articulating
basically with pedicle.
Setaceous: the subsegments of flagellum, tapering terminally, with seta
Filiform: the flagellum subsegments alomost equal in size, rod shaped, with
blunted end (locust)
Monliform: the subsegments like beads of necklace (white ant)
Capitate: the terminal sub-segments enlarge suddenly, cap shaped (flour
Clavate: with large diametered subterminal segments, like knob (butter
Pectinnate: each sub-segment carry a thin process on one side, comp
shaped (♀ moths)
Bipectinate: comp on both sides (♂ moths).
Lamellate: leaf like subsegments, overlapping each other as a fan (Scarab
Geniculate: angled short flagellum, elbow-shaped (honey bee).
Plumose: setaceous type flagellum, but carring tufts of long hairs on both
sides, feather shaped (♂ mosquito)
Pilose: hairs shorter & less than plumose (♀ mosquito)
Aristate: short, rod shaped & unsegmented flagellum, carries a thread like
process called arista covered with hairs (house flies)
Stylate: blade like subsegments with pointed apor (Tabanus fly)
THE MOUTH PARTS
•Typically evident in cockroach.
•Modification is a functional adaptation
-By reduction of un-needed parts
-Enlargement of the impotent parts or change in its shape
-Development of accessory parts
M. P. OF BUTTERFLY (SUCKING TYPE)
Modifications according to functional
• Reduction of –Labrum
• Absence of –mandible & hypoharynx.
• Labium represented only by palps (tactile)
• Maxillae fused together & modified into a
sucking proboscis (the functional organ).
Proboscis: retractile, tubular, &
developed from the two galeae by its
elongation and rolling into a semi-tube
within inter-locked hooks.
M. P. OF HONEY BEE WORKER(BITING LAPPING TYPE)
Reduction of hypopharynx & labrum.
- Mandibles: 2 flattened rectangular
plates, no teeth, no molar (used in
cutting soft wax).
- Maxillae: cardines rod shaped, stipi
fused to form lorum. The galeae
enlarged sheath. Lacinia, a small lobe
at the base of the galea.
- Labium: tongue-like proboscis. Fused,
extended & rolled glossae.
Labrum-Epipharynx: elongated flap roofing the
Proboscies & covering the underlying mouth
Mandibles: pair of thin, hollow long bristle, with
pointed sharp ends. Adapted for piercing blood
vessels & sucking their contents.
Hypopharynx: a sword-shaped structure
extending between the mandibles & underneath
the labrum-epipharynx. It has sharp edges for
tearing the skin.
Maxillae: a pair of styles with serrated ends for
scratching the skin (modified galea)
Labium: elongated, thick walled (protective
sheath for the rest parts)
MOUTH PARTS OF ♂ MOSQUITO
Not blood sucker (no mandibles)
Maxillae (greatly reduced)
Hypopharynx: fused with labium
Maxillary palps (4 segments “club-shaped”)
Don not forget the sexual dimorphism in the antennae.
M. P. OF HOUSE FLY (SPONGING TYPE)
The head capsule is protruded into a funnel-shaped Rostrum.
The pharynx extends through the rostrum as a narrow pipe.
Labium: a thick double walled ( haustellum).
Labrum-Epipharynx: consists of labrum,
fused with the extended roof of the pre-oral cavity,.
Hypopharynx: a tongue-like structure resting
along the floor of the haustellum, for receiving the
Food-Meatus: a narrow channel enclosed
between the hypopharynx & the labrum-
epipharynx. Extended till the mouth opening
Labellae: 2 big sponge lobs carried on the tip
of the haustellum, for passage of saliva to dissolve
food before absorption.
The mandibles: absent
The maxillae: reduced.
THORACIC REGION & ITS APPENDAGES
Carrier to the locomotory organs.
Each of the three segments carries one pair of jointed leg.
Dorsally on each of meso- & metathorax it posses one pair
of wings and spiracles.
Typically structured from 3 sclerotized plates:
Tergite:( dorsal in position)
With supporting function from all sides, provide
articulation for wings & legs, protection of the spiracles.
o Between each segments an articulating and bending inter-
segmental membrane, for bending & stretching.
FORMS OF THORACIC SEGMENTS
Only in primitive insects & immature stages the
thoracic segments similar in shape & equal in
The descriptions of the typical structure.
The modification in different insects to suit the mode of locomotion or non-
locomotory functions (food collecting).
Most adult insects posses 2 pairs of wings (on
meso- & metathorax)
In flies & mosquitoes, the hind pair is reduced
Wings are not modified legs as in birds & bats,
but are additional locomotory organs.
The base of wing articulates with the tergum
& pleuron of the segment carrying it. This
facilitates rotation of the wing during flight in
various directions in relation to the body axis.
TYPICAL STRUCTURE OF THE WINGS
Triangular, 3 regions (Jugum,
Vannus, & Remigium)
Wing Axil, posses small sclerotic
(support & articulation)
In the hind wings of most insects the 3
regions are separated from each other
by 2 folds
This enables the insect to fold the
hind wings during repose & unfold
them during flight.
Histologically, a wing is
analogous to a plant leaf,
contains double layer of
flattened cells covered with
extremely thin cuticle
Enclosing in between the
wing veins (for aeration)&
space for few blood cells
The wing surface carries
hairs, scales or spicules
For fixing the for-wing with the hind-wing
This coupling enables the insect to resist the
opposing action while flying at considerable
1- In honey bee: the costal margin of the hind-wing
posses row of curved hooklets, that anchored to a
chitinous ridge of the anal margin of fore-wing,
(during Nuptial flight)
2- In some moths: the costal margin carries a process
that can fit within a loop extending from the anal
3- In other moths: the anal margin of the fore wing has
2 clefts enclosing a lobe between them, coupling by
simple overlapping between the lope & the costar
margin of the hind-wing.
TYPES OF WINGS
Wings of different insects differ in size, shape, texture & other
Fore-wing usually differ from the hind-wings of the same
Function of wings:
1- flight ( rotationary vibrations effected by thoracic muscles).
2- Abdominal protective shield (fore-wing Elytera of beetles).
3- Balancing organs (modified hind-wing halteres in flies &
4- Sound-producing organs for calling mates (♂ crickets).
5- Important for insect classification (different types & mode of
1- Tegmina (Leathery)
2- Elytra (elytron)
4- Hairy type
5- Lace type
7- Membranous type
8- Haiteres (Balancers)
ABDOMINAL REGION & ITS APPENDAGES
It carries paired spiracles laterally
The gonophores postero-ventrally & the anus
Contraction of abdominal muscles facilitates
hatching, molting & oviposition.
In apodous stages it was responsible for
locomotion (vermiform movements).
THE ABDOMINAL SEGMENTS
Number: variable, the decrease in number is due to fusion, atrophy, or
Typical structure: a tergite, a starnite & 2 pleurites
Types: distinguished into:
1- Visceral S: constitute the major part of the abdomen next to the thorax
2- Genital S: the subterminal 2 segments carries the gonopore & genitalia
3- Post-Genital (Anal or Caudal) S: the terminal one or 2 segments carry
Anus & Cerci (similar in both sexes)
Structural modifications are common in the genital &
caudal segmants. Examples are:
Last tergite in most big insects is split into 3 plates (2
lateral paraprocts & a median epiproct) for anus
protection and facilitating egesting
7th sternite in ♀ cockroach, enlarged & boat shaped to
protect the genitalia & holds the egg capsule
9th sternum in ♂ cockroach enlarged to protect the
genitalia & carries 2 thin sensory processes (Styli)
Last sternum in ♀ lice is clefted to facilitate mating &
Terminal 3 segments in ♀ house fly reduced to retractile
telescoped tubules for oviposition
• During immature stages some visceral segments carry paired
appendages for locomotion or aquatic breathing. In most of them
they were disappeared before maturity , but in Collembola they
1- Prolegs: Caterpillars (5 pair of prolegs joined the ventral side
of 3rd, 4th, 5th, 6th, & 10th abdominal segments , they ends with
ring of curved hook-lets for clinging facilitation & climbing.
Additionally, they help the thoracic legs but differ from them in
position and structure (disappeared in the adult stage)
Tracheal gills: feather-like lateral extensions of the
anterior 7 abdominal segments (May fly nymphs)
Springing apparatus: found in Collmbola, consists of
1- Colliphore (=Adhesor for adhesion)
2-Hamula (Clasper), hold the furcula during repose
3-Furcula (Spring) a long biforked flexible process extending from the latst (5th)
Springing takes place as follows
a. The fluid is withdrawn from the vesicles of colliphore, then collapse & the
insect gets free from substratum
b. The furcula is released from the clasper to return backwards in a sudden
movement (so, insects springs forwards swiftly)
ANAL (CAUDAL) APPENDAGES
One pair carried by the last segment in both sexes
With different shape & size in different insects
All of them are tactile in function
Caudal gill plates, the terminal segment carries 3 leaf-like
thin walled gill plates for aquatic breathing (Damselfly
TYPES OF CERCI
Short unsegmented (Locust)
Short, spindle shaped & segmented (cockroach)
Long segmented & setaceous (silverfish)
Forceps-shaped with serrated inner edges (ear-wigs) (for defence & preying)
GENITAL APPENDAGES (GENITALIA)
Penis: median hollow organ, joining the 9th sternum basally &
carrying the ♂ gonopore (copulatory)
claspers: one pair in some insects, enclosing the penis in-between
styli: in cockroaches only, one pair of thin unsegmented process
♀ GENITALIA (OVIPOSITOR)
8th & 9th segments modified to an egg-laying
apparatus (by governing the egg deposition)
Honey bee, cockroach, grasshopper & parasitic
Typical structure: 3 pairs of valves, enclosing the
Forms of ovipositors: depending on differ in shape &
size of valves, for different oviposition habits & other 2ry
Function: 1- digging tunnels (Locust)
2- tearing plant leaves (Thrips)
3- piercing & narcotizing (parasitic wasps)
4- defense & attack (honey bees)
In worker only for defense or attack
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CITATION & REFERENCES
1- Text book of “Fundamentals of applied entomology”. 3rd
edition, by Robert E. Pfadt. Macmillan publishing Co.,
INC. New York, 1971.
2- note book of “Entomology” 2nd year biology, published by
the Zoology Dep., Faculty of Science Mansoura University.
http://www.youtube.com/watch?v=Jpcpn5NX62c (honey bee
http://www.youtube.com/watch?v=L1bi-8uRCaU (house fly )
Recommended Text: The Insects, Structure and Function, by
Recommended Text: Evolution of the Insects, by Grimaldi
Recommended Text: Principles of Insect Morphology, by