Download Chewing – lapping mouth parts

L . 2 . Medical Entomology
M.S.C. IZDIHAR A. ALWAN
Class :- Insecta
A look at the outside of an insect :
Exoskeleton
As typical arthropods , insects have a chitinous cuticle secreted by the hypodermis , a
single layer of columnar epithelial cells of ectodermal origin which is cast off or
molted at intervals to permit growth and metamorphosis .
The chitinous cuticle serves as an exoskeleton (integument ) , thus as both a body
covering and a place for attachment of muscles . Heavily chitinized areas or plates
of cuticle are connected by thinner lightly chitinized areas , thus permitting movement
and some degree of expansion as , for example when the abdomen of a feeding female
mosquito fills with blood . Insect muscles are striated and often capable of
extraordinarily rapid contraction . The cuticle consist of three layers are Endocuticle ,
Exocuticle and Epicuticle which is impermeable to water .
When a developing insect has grown too large for its cuticle , the hypodermis lays
down a new , thin , elastic cuticle under the old one . The cuticle then splits and the
insect emerges from it , this process termed molting or ecdysis .
Body division of insects :1- The Insect Head :
* Mouthparts
Labrum ( 1 ) " Upper lip " , Mandibles ( 2 ) " Jaws " , Maxillae ( 2 ) " More jaws " ,
labium ( 1 ) " Lower lip " and Hypopharynx ( 1 ) " Tongue – like , bears openings of
salivary ducts "
Different arrangements and forms of these parts makeup the principal types of insects
mouths :1
Chewing mouth parts :. It seems that this is the most primitive type of mouth parts .
Cockroaches , beetles and chewing lice are examples for this type .
Sponging mouth parts : found in large numbers of the non- biting flies such as the
house flies and flesh flies have this type of mouth parts .
Piercing – sucking mouth parts : are possessed by insects such as mosquitoes ,
assassin bugs , stable flies , sucking lice and fleas . these insects pierce the skin of
animals in order to suck the blood from them . These mouth parts are characteristic of
most the insect vectors of disease .
Cutting – lapping mouth parts : This is restricted to a limited number of adult flies
feeding as parasites up on blood from mammal hosts . Black flies and horse flies are
good examples .
Siphoning mouth parts :- The mandibles and labium are reduced or lost and have no
role in food ingestion , this type found in butterfly
Chewing – lapping mouth parts : adult hony bees and bumble bees have mouth parts
that are modified in still another form in order to utilize liquid food in this case nectar
and honey .
* Eyes :
Compound eyes : individual units are facets or ommatidia 28000 ommatidia
Simple eyes " Ocelli " : small and usually a single lens .
* Antennae :
Two basal segments are the scape and pedicel . The filament is comprised of several
segments ( actually pseudo-segments lacking independent musculature ) .
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Types of Antennae
a- Setaceous : hair – like ( Cockroach ) .
b- Filiforn : thread – like (Grasshopper ) .
c- Moniliform : bead – like ( Termites ) .
d- Serrate : sawtoothed ( beetles ) .
e- Pectinate : comb – like ( moth and beetles ) , Bipectinate ( Bombyx mori ) .
g- Capitate : head – like , less enlarged at the tip would be clublike ( Tenebrio ) .
h- Geniculate : elbowed ( honey bee ) .
i- lamellate : plate – like ( beetles ) .
j- Plumose : feather – like ( male mosquite ) , pilose ( female mosquite ) .
k- Stylate ( horse fly ) .
l- Aristate ( house fly ) .
m- Clavate ( Butterflies )
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2- The insect thorax : three distinct segments :Prothorax : bears 1 pair of legs .
Mesothorax : bears 1 pair of legs , 1 pair of wings .
Metathorax : bears 1 pair of legs , 1 pair of wings .
* Legs : are segmented , the names for each segment are :- coxa , trochanter , femur ,
tibia and tarsus . The tarsus may be comprised of multiple segments the terminal
segment usually bears claws .
Legs may be modified for specific purposes :Jumping : ( grasshoppers , fleas ) .
Running " walking " : ( ground beetles , cockroaches ) .
Clinging : ( lice ) .
Grasping " manting " : ( giant water bugs , mantis ) .
Digging : ( mole – cricket ) .
Swimming : ( water beetle ) .
Cleaning legs and Collecting legs : ( honey bee ) .
* Wings :
Mesothoracic wing = forewing , Metathoracic wing = hindwing . wing veins and cells
between veins are named according to the standared system illustrated below :
Wing modifictions :Halteres ( halter ) : knob – like reduced hind wings of Diptera .
Elytra ( elytron ) : Hardened , protective forewings of Coleoptera .
Hemielytra : Half – hardened , Half – membranous forewings of Hemiptera .
Hairy wings : modified wing structure of the Thysanoptera ( Thrips ) .
Scaly wings : Lepidoptera and some Diptera .
Tegmina (Leathery) wing : cockroaches and grasshoppers.
Membranous wing : Hony bee and Wasp .
3- The insect abdomen :
The abdomen consist of 11 or fewer segments , of which the terminal ones are
modified
* Reproductive appendages
Male genitalia and Ovipositor : egg laying apparatus ( may be modified for other
purposes ) .
* Non- reproductive appendages
Caudal fillament , Anal styli and Anal cerci .
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