MANSOURA UNIVERSITY

INSECT MORPHOLOGY

For 2nd year biology

By

Dr. Zeinab Abu-Elnaga

•Entomology 2014 zenab_77@mans.edu.eg Zoology Department, Faculty of Science http://zaboelnaga.synthasite.com

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COURSE OUTLINES

o General introductory lecture.o External body morphology of insects and its modifications

Body apertures

The head capsuleStructureCephalic appendages

1.The antennae

2.The mouth parts

The thorax1.The wings

2.The legs

The abdomen1.The cerci

2.The genitalia

3.The styli

4.Stinging apparatus

5.Springing apparatus

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Lecture 1

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GENERAL LECTURE

INSECTS Systematic Position: 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) .

General Characters:A- Characters common between insects and other arthropods: Triploblastic coelomate with bilateral symmetry Segmented body and jointed appendages. Exoskeleton. 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).

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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.

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AT

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StructuralSize & shapeThe ExoskeletonAdvanced locomotory organsThe mouth partsCentral nervous systemThe reproductive capacityThe digestive systemThe fat tissue

BehavioralOviposition hapitsProtection of quiescent stagesPeriodicity of activityHibernation & diapauseFeeding habitsMimicry & protective coloration

BiologicalDiversity of dietModes of reproductionLife cycle durationMetamorphosisparasitism

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ECONOMIC IMPOTENCE OF INSECTS

Blood sucking insects

(mostly temporary ecto-

parasites on man or

permanent ecto-parasite).

Disease transmission

Myasis to man & animals

Spoils our food & drink.

damage of cloths &

furniture

Caused by insects which

infest crop plants &

beneficial animals.

Plant pests: locusts, larvae of

many moths, thrips, fruit

flies, ……..ect.

Animal pests: warble flies

attack sheep & cattle,

causing decreased efficacy,

milk, & flesh…….

Direct Indirect

A-Injurious insects

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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

& inks).

Pharmaceutical materials.

Cross pollination.

Improvement of soil properties

(ground beetles).

Source of food for birds &

fishes, used, in turn food for

man.

Discovery of juvenile hormone.

Some of them used as

biological control agents.

Direct Indirect

B- Benefits of insects

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Lecture 2

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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.

brain

Mouth parts

antennae

Compound eyes

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THE HEAD CAPSULE

Corresponds to the cranium of vertebrates.

The typical structure evident in locusts & cockroaches.

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POSITIONS OF THE HEAD

Pro-gnathous: head extended

longitudinally with body axis (m.p

are pointed forward, Weevils)

Hypo-gnathous: head

perpendicular to longitudinal

body axis (m.p pointed

downwards, Locust)

Opitho-gnathous: head bent

underneath thorax during rest

(m.p pointed backwards, Aphids)

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The Antennae 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.

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Setaceous

Filiform

Moniliform

Serrate

Capitate

Lamellate

Aristate

Pectinnate

Bipectinnate

Plumose

Pilose

Clavate

Geniculate

Stylate

flate

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Setaceous: the subsegments of flagellum, tapering terminally, with

seta shape (cockroach).

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 beetles).

Clavate: with large diametered subterminal segments, like knob

(butter flies)

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 beetle).

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)

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Lecture 3

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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

Cockroaches.flv

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M. P. OF BUTTERFLY (SUCKING TYPE)

Modifications according to

functional adaptation.

• 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.

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M. P. O

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(S

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M. P. OF HONEY BEE WORKER(BITING LAPPING TYPE)

Reduction of hypopharynx & labrum.

Modifications

- 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.

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M. P. O

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)Honey bee feeding

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Honey Bee.flv

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MOUTH PARTS OF ♀ MOSQUITO (PIERCING-

SUCKING TYPE)

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♀ ANOPHELES MOSQUITO

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Modifications: Labrum-Epipharynx: elongated flap roofing

the Proboscies & covering the underlying

mouth parts.

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)

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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.

♂Anopheles

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♂ CULEX

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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.

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M. P. O

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Modifications:

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 salivary duct.

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.

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Lecture 5

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THORACIC REGION & ITS APPENDAGES

Thorax

Wingsdorsally

Legsventrall

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THORACIC REGION

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)

Sternite: (ventral)

Pleurites: (lateral)

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.

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FORMS OF THORACIC SEGMENTS

Only in primitive insects & immature stages the thoracic segments similar in shape & equal in size.

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THORACIC APPENDAGE

The descriptions of the typical structure.

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MODIFICATIONS

The modification in different insects to suit the mode of locomotion or non-

locomotory functions (food collecting).

Running Cockroach

JumpingLocust

Walking upside-down

House fly

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SeizingFore-leg

Prey mantis

BurrowingFore-leg

Gryllotalpa

Swimming

Hind-legsWater beetles

Food collecting Hind-leg of Honey bee

worker

Clinging Lice

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Lecture 6

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THE WINGS

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.

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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.

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HISTOLOGICAL STRUCTURE

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

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WING COUPLING

For fixing the for-wing with the hind-wing

This coupling enables the insect to resist the

opposing action while flying at considerable

heights.

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 margin.

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.

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WIN

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TYPES OF WINGS

Wings of different insects differ in size, shape, texture &

other structural details.

Fore-wing usually differ from the hind-wings of the same

insect.

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 &

mosquitoes).

4- Sound-producing organs for calling mates (♂ crickets).

5- Important for insect classification (different types & mode

of development.

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1- Tegmina (Leathery)

Cockroach

2- Elytra (elytron)

Coleopterous

3-Hemi-elytra

Hemiptera

4- Hairy type

Thrips

5- Lace type

Neuroptera

6-Scaly type

Lepodoptera

7- Membranous type

Hymenoptera

8- Haiteres (Balancers)

Diptera

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Lecture 7

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ABDOMINAL REGION & ITS APPENDAGES

It carries paired spiracles laterally

The gonophores postero-ventrally & the anus

terminally.

Contraction of abdominal muscles facilitates

hatching, molting & oviposition.

In apodous stages it was responsible for

locomotion (vermiform movements).

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THE ABDOMINAL SEGMENTS

Number: variable, the decrease in number is due to fusion, atrophy, or

modification.

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 (no

appendages)

2- Genital S: the subterminal 2 segments carries the gonopore & genitalia

(sexual function)

3- Post-Genital (Anal or Caudal) S: the terminal one or 2 segments carry

Anus & Cerci (similar in both sexes)

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MODIFICATIONS

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 &

oviposition

Terminal 3 segments in ♀ house fly reduced to retractile

telescoped tubules for oviposition

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VISCERAL APPENDAGES

• 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

remain

• types:

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)

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Tracheal gills: feather-like lateral extensions of the

anterior 7 abdominal segments (May fly nymphs)

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SPRINGING APPARATUS

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)

segment.

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)

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Lecture 8

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ANAL (CAUDAL) APPENDAGES

1- Cerci:

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 nymphs)

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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)

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GENITAL APPENDAGES (GENITALIA)♂ 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

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♀ GENITALIA (OVIPOSITOR)

8th & 9th segments modified to an egg-laying

apparatus (by governing the egg deposition)

Honey bee, cockroach, grasshopper & parasitic

wasps

Typical structure: 3 pairs of valves, enclosing the

gonopore

Forms of ovipositors: depending on differ in shape &

size of valves, for different oviposition habits & other 2ry

functions

Function: 1- digging tunnels (Locust)

2- tearing plant leaves (Thrips)

3- piercing & narcotizing (parasitic wasps)

4- defense & attack (honey bees)

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FORMS OF OVIPOSITORS

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STIN

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Modified ovipositorIn worker only for defense or attackStructure:

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Please consider the following in your comments about the course.

Would you prefer weekly quizzes rather than the “practice quizzes?

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COURSE EVALUATION

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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://images.google.com/images?hl=en&um=1&q=Forms+of+ovipositors+of+insects&sa=N&start=100&ndsp=20http://en.wikipedia.org/wiki/Insecthttp://www.earthlife.net/insects/anatomy.htmlhttp://www.amazon.com/Principles-Insect-Morphology-Comstock-Book/dp/0801481252#readerhttp://www.youtube.com/watch?v=Jpcpn5NX62c (honey bee

feeding)http://www.youtube.com/watch?v=L1bi-8uRCaU (house fly )http://www.youtube.com/watch?v=7V_GBQclQfc (mosquito)http://www.youtube.com/watch?v=daYvNM2IuOg (cockroach)

Recommended Text: The Insects, Structure and Function, by Chapman. Recommended Text: Evolution of the Insects, by Grimaldi and Engel. Recommended Text: Principles of Insect Morphology, by Snodgrass