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Cockroach
Cockroach is a common insect living in warm humid places. Cockroaches
are quite common in kitchens, bathrooms, gutters and hotel kitchens. They
are nocturnal. They are spread worldwide. The scientific name of
cockroach is Periplanata americana.
Phylum - Arthropoda.
Class – insecta
Order Dictyoptera
es. Cockroaches
el kitchens. They
ific name of
External characters
The body of cockroach is long, dorso-ventrally
flattened and of reddish brown colour.
An adult cockroach is 25 to 45 mm long and 8
to 12 mm broad. The size of male is slightly
bigger.
The body is protected by an exoskeleton of hard
and chitinous material called sclerites. Sclerites
are arranged as terga and sterna in all segments
of the body.
The body is clearly divided into three parts head, thorax and abdomen.
.
Head
The head of cockroach is triangular. It is located at the
anterior end and is almost at a right angle to the rest of the
body
. The head is formed by fusion of six segments. A pair of
sessile compound eyes occur on the head. Eyes are kidneyshaped. Two long antennae occur. Antennae can be rotated
in all directions
At the anterior end of head, mouth is located.Mouth parts
consist of a pair of mandibles, a pair of first maxillae, lubium
, labrum and . hypopharynx. Salivary glands open at its
basal region.
Thorax
•Thorax consists of three segments prothorax, mesothorax and metathorax
•One pair of walking legs having five
segments ie. Coxa, trochanter, femur,
tibia & tarsus.
•The first pair of wings develops from the
dorsal side of mesothorax. These wings
are horny and protective.
•The second pair of wings develops from
the dorsal side of metathorax.
Abdomen
•
Abdomen is made up of ten segments. Each segment has
a dorsal tergum, a ventral sternum and lateral pleurae.
•
A pair of anal cerci are associated with the tenth tergum.
Anal cerci are phono-receptor structures.
• In male cockroach, a pair of anal styles develop from ninth
sternum.
• In female cockroach, the eighth and ninth sterna jointly
form a genital pouch. The seventh sternum is keel-shaped.
• The male genital opening occurs in mid-ventral region of
ninth segment. The female genital opening opens in the
eighth segment.
Digestive System
• The alimentary canal of cockroach
is divided into three parts Foregut, midgut and hindgut.
• The cavities of foregut and hindgut
are lined with cuticle. Mouth is
located at the posterior end of a
preoral cavity which is surrounded
by mouthparts.
• Pharynx follows the mouth.
Salivary glands open on the
ventral side of hypopharynx.
• Oesophagus follows pharynx.
The posterior region of
Oesophagus expands and forms a
crop
• The crop opens into a gizzard.
The wall of gizzard is muscular.
•There are six chitinous teeth in its cavity. Food is
grinded in gizzard.
•At the posterior end of gizzard a sieve-like structure
occurs which is formed by chitinous bristles.
•The region upto gizzard constitutes fore-gut. Gizzard
opens into midgut.
•Eight, tubular hepatic caeca occur in midgut. They
secrete digestive juices.
•Midgut opens into hindgut where malpighian tubules are
present. These act as excretory organs.
•Rectum opens to the outside through anus located
under the tenth tergum.
The circulatory system
• The circulatory system of cockroach is of
'open' type, called haemocoel
• It consists of plasma and cells known as
hemocytes.
• In the thoracic and abdominal region, a
tubular structure made up of thirteen
funnel-like units, occurs along the middorsal region. This keeps the blood
circulating.
•
The first three units occur in thorax and the
remaining ten occur in abdominal region.
Each unit can be considered a heart.
THE RESPIRATORY SYSTEM
• The respiratory system of
cockroach is well developed. It
consists of a branched network
of tracheal tubes spread
throughout the body.
• The tracheal tubes open on the
surface of the body through
openings called spiracles. Ten
pairs of spiracles occur.
• Two pairs of spiracles occur in
thoracic region and eight pair of
spiracles occur in the abdominal
region.
The excretory system
• The excretory units are malpighian tubules present at
the union of midgut and hindgut.
• They absorb nitrogenous waste and empty them into the
cavity of hindgut.
• Special nephrocyte cells and fat bodies also help in
excretion.
• Some excretory substances are stored in the chitinous
exoskeleton.These are also discarded alongwith the
exoskeleton during moulting.
The nervous system
• The nervous system of cockroach is made up of paired
ganglia, nervecords and nerves.
•
In the head brain or supraoesophageal ganglia are
located. They are connected with suboesophageal
ganglia through circum-oesophageal commissures.
• Three pairs of ganglia occur in thorax region and ten
pairs of ganglia occur in abdominal region. Nerves arise
from ganglia.
SENSE ORGANS
• Amongst sense organs in cockroach, antennae,
eyes, maxillary palps, tarsus of walking legs and anal
cerci are included.
•Eyes of cockroach are compound. A compound eye
is made up of about 2000 ommatidia. It creates a
mosaic image and locates any movement quickly
• The anal cerci are sensitive to sound.
•Antennae, maxillary palp and tarsus are tactile in
nature
Male reproductive system
• Male cockroach possesses one pair of testes.
They are located in fourth and fifth abdominal
segments
• Two vasa efferentia run towards posterior side
and open into the ejaculatory duct. Seminal
vesicle is associated with the ejaculatory duct.
• Ejaculatory duct opens to the outside through the
male genital opening.
• Male gonapophysis are located in the male genital
opening. They play an important role in
copulation.
• A mushroom gland occcurs in segments 6 & 7
• Another long and flat gland called acessory gland
occurs on the ventral side of ejaculatory duct
The female reproductve system
• Female cockroach possesses one pair of
ovaries. They are arranged in segments 4, 5
and 6 on lateral sides.
• Ovarian tubules of each line join and form an
oviduct. Oviducts from two ovaries join and
form uterus. Uterus opens into vagina.
• Vagina opens through a vaginal opening to
the outside through segment number eight
• A pair of branched collateral glands occur as
accessory reproductive glands which open in
the vaginal duct.
• Female gonapophysis occur in the female
genital opening.