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BIOLOGY
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2. cOckrOAch
The cockroach is the most common pest of food industries,
hotels, kitchens, warehouses etc. It is one of the arthropods
belonging to the class insecta. It has four common species
found in India.They are :
Blattella germanica, the German cockroach,
Blatta orientalis, the Oriental cockroach,
Periplaneta americana, the american cockroach (the most
common species in the world) and
Periplaneta australasiae, the australian cockroach.
SYSTemATIc POSITIOn
Phylum – arthropoda
Class – Insecta
Subclass – Pterygota
Division – exopterygota
Order – Orthoptera
Genus – Periplaneta
Species – americana
Cockroach is considered suitable type for the study because it
shows insect structure in its fundamental form, it is harmless
to handle, its size is convenient for study and it is available
throughout the year.
hABITAT
Cockroaches are found in warm, dark and damp places. They
commonly inhabit kitchens,restaurants,store houses,godowns,
railway wagons, ships, etc. They are numerous in underground
drains.
hABITS
They are nocturnal insects preferring darkness and become
active during night, but remain hidden under some objects
and take rest during day time. Cockroaches are omnivorous
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The content for PMT Biology is very vast. It does not allow
students to engage in enquiry so as to develop meaningful
knowledge. Essential topic for PMT is presented here
to enable students grasp the topic, analyse the kind of
questions appearing in PMTs, practice and scorE HIGH.
in diet, feeding on almost all kinds of food matter including
human food, paper, leather, cloth and even dead bodies of their
fellows. They prefer starch containing food. Cockroaches are
cursorial insects, viz. run very fast.They fly very rarely as they
are not good fliers.
Cockroaches are unisexual (male and female sexes are found
in different individuals) and show sexual dimorphism i.e.,
one sex can be distinguished from the other externally. They
are oviparous (laying eggs). The young ones called nymphs
resembles adults, except being smaller. Parental care is seen
in them.
mOrPhOLOGY Or exTernAL chArAcTerS
Shape, Size and Colour
The body is dorsoventrally flattened, elongated and bilaterally
symmetrical. The adult cockroach is about 2 to 4 cm in length
and about 1 cm in width.The colour is shining reddish brown.
Male cockroach Female cockroach
1. abdomen is relative long
and narrow.
abdomen is relatively short
and broad.
2. Seventh tergum covers
only the eighth tergum in
the abdomen.
Seventh tergum covers the
eighth and ninth terga in
the abdomen.
3. all the nine abdominal
sterna are visible.
Only the first seven
abdominal sterna are
visible
4. There is no brood pouch. a brood pouch is formed by
the seventh, eighth and ninth
abdominal sterna.
5. Ninth abdominal sternum
bears a pair of anal styles.
There are no anal styles.
6. Genital aperture lies
below the anus on one
of the gonapophyses.
Genital aperture lies on
the 8th sternum within the
brood pouch.
7. There are only 3
gonapophyses
There are 3 pairs of
gonapophyses.

3. Exoskeleton or cuticle
a non-living brown coloured, hard, jointed and chitinous
exoskeleton composed of several plates or sclerites cover the
entire body. The adjacent sclerites are joined together by thin,
soft, flexible articular or arthrodial membranes to allow
movement.
Functions of cuticle
Thick cuticle of arthropods is like steel to modern man, and is
primarily responsible for their great success. It is useful in many
ways as follows :
Provides support, rigidity and protection.
Waxy layer prevents loss of water due to evaporation, thus
enabling insects to live in relatively dry environments.
Cuticular invaginations offer points of attachment for
muscles. Jointedness of cuticle of body segments and
appendages make accurate complicated movements
possible.
Cuticular lining of fore and hind guts protect their epidermis
from abrasions by passage of food.
Melanin pigments within cuticle provide protective
colouration.
Many of the cuticular outgrowths form sensory receptors.
Body
body of cockroach is distinctly divided into segments grouped
into 3 well - defined regions or tegmata – head, thorax
and abdomen.
Head
Head is formed by the fusion of 6 embryonic segments and is
small and roughly triangular in shape. It is attached to thorax
by a short and narrow neck or cervicum and can be moved by
neck muscles in different directions.
The whole of head is covered by sclerites constituting the
head capsule. The top or vertex is formed by two epicranial
plates jointed in front by an inverted g-shaped coronal or
epicranial suture. an impaired triangular sclerite called frons
lies between the arms of epicranial suture.
below the frons is a narrow, rectangular sclerite, the clypeus.
There is a faint horizontal line,the frontoclypeal suture between
the clypeus and the frons.
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a movable plate called the labrum articulates with the lower
edge of the clypeus by labroclypeal suture.
Two cheek sclerites, the genae, lie vertically just below the
eyes at the lateral side.
Head bears a number of jointed appendages.On each dorso-
lateral side of head is a large reniform and black compound
eye. Just in front of each eye is a long, slender and multi-
segmented antenna. Inner to the base of each antenna is a
small, rounded and whitish area or fenestra, representing a
simple eye or ocellus.
Lower end of head bears the preoral cavity and mouth,
surrounded by mouth parts. Such a head with mouth parts
directed downwards is called hypognathous.
Thorax
The middle region of body or thorax consists of 3 distinct
segments called, from in front backwards, the prothorax,
mesothorax and metathorax.
each thoracic segment is enclosed by four chitinous skeletal
sclerites.a dorsal tergum, a ventral sternum and two lateral
pleura (sing. pleuron). The tergum of the prothorax is also
called pronotum, which is the largest sclerite and projects
forwards to cover the neck and head.
each thoracic segment bears ventrally a pair of 9 jointed
walking legs, while mesothorax and metathorax each bear a
pair of wings dorsally.
Two pairs of tracheal openings or spiracles are present on
the lateral pleura of thorax.
Abdomen
The posterior region of body is called abdomen. It is broader
than thorax and dorso-ventrally flattened. abdomen of adult
consists of 10 segments while embryo has 11 segments. Not
all segments are visible externally, the hinder segments remain
somewhat concealed.
8 pairs of tracheal openings or spiracles are present on lateral
pleura of first 8 abdominal segments.
The arthrodial membrane between the fifth and sixth
abdominal terga is depressed on either side to form a stink
gland.The stink glands produce a secretion pheromone, that
gives a characteristic stinky (foul) smell.
anus lies below 10th
tergum between 4 podical plates.
10th
segment in both sexes bears a pair of small, filamentous
and sensory anal cerci. In females, the 7th
sternum is boat
shaped and together with the 8th
and 9th
sterna forms a
brood or genital pouch whose anterior part contains female
gonopore, spermathecal pores and collaterial glands.
In males, genital pouch or chamber lies at the hind end of
abdomen bounded dorsally by 9th
and 10th
terga and ventrally
by the 9th
sternum. It contains dorsal anus, ventral male genital
pore and gonapophysis. Males bear a pair of short, thread-like
anal styles which are absent in females.

4. inner, hard plate-like lacinia. The latter tapers into two
sharp claw like projections. Lacinia also bears numerous
strong sensory bristles at its inner surface.
Exopodite : Maxillary palp represents exopodite.
both maxillae act as accessory jaws. They work sideways
to masticate food and to convey food morsels into oral
cavity.
(iv) Labium (Second maxillae)
Labium or lower lip is the appendage of 6th head segment.
It is the posterior-most of all mouth parts. It is formed by the
fusion of two maxilla-like embryonic appendages or second pair
of maxillae. fused protopodite is 3-segmented consisting of
a large proximal submentum, a small middle mentum and
a distal prementum.
The partially fused endopodites form a tongue-like ligula.
each half of ligula consists of an inner glossa and an outer
paraglossa, corresponding with lacinia and galea respectively.
Prementum bears, on each side, a 3-jointed sensory labial palp
borne on a basal projection, the palpiger. Terminal segment
of palp is covered thickly with sensory setae.
The labium does not take active part in feeding. However,
glossae and paraglossae prevent the loss of food particles
from mandibular action. The labial palps respond to taste and
smell.
(v) Hypopharynx
It is a small concial fleshy structure, hanging in between the
two maxillae in front of the labium and acts like tongue.
an efferent salivary duct carrying the saliva from the salivary
glands opens near the base of the hypopharynx.
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APPenDAGeS Of cOckrOAch
Main appendages include: antennae and mouth parts on head,
legs and wings on thorax and external genitalia on abdomen.
Antennae
antennae are a pair of long, slender, whip-like, and many-
jointed movable appendages, found on head. an antenna is
attached close to the inner side of compound eye in a circular
socket enclosed by a ring-like antennal sclerite, and freely
articulating by a thin membrane.
It consists of a large basal segment, the scape, followed by
a short and cylindrical pedicel, and a long many-jointed
flagellum.
The antennae bear tactile and olfactory receptors and
are sensitive to touch and smell. Male cockroach has longer
antennae than female.
Mouth parts
Mouth parts are head appendages surrounding the
mouth. These consist of the labrum or upper lip, a pair of
mandibles, a pair of maxillae, the labium or lower lip and
the hypopharynx.
They are of the mandibulate type (i.e., biting and chewing type)
and remain unspecialized due to its omnivorous diet.
(i) Labrum
Labrum or upper lip is the appendage of 3rd
head segment.
It is broad, chitinous flap, which hangs from the distal end
of the clypeus. It is a also called as upper lip. a thin plate,
the epipharynx, is fused to the inner surface of labrum. The
epipharynx bears the organs of taste. The labrum holds the
food particles during the feeding.
(ii) Mandibles
These are appendages of 4th
head segment. These are small,
triangular,and strongly sclerotised structures.They are attached
with the sides of head capsule and articulate by means of a
condyle with the gena of same side.
Inner margin of each mandible is made of two small cutting
or serrated lobes, distal incisor and proximal molar, each
bearing 3 tooth-like denticles of thickened cuticle. Proximal to
molar lobe is a membranous lobe, the prostheca, that bears
sensory hairs. Mandibles work like jaws.
(iii) Maxillae (First maxillae)
These are appendages of 5th
head segment and known as
first pair of maxillae. They lie beneath the mandibles on either
side on the head capsule. each maxilla consists of three parts:
Protopodite : It is a basal portion and made up of two
parts- the proximal cardo and the distal stipes. both the
parts are bent at an angle to each other.
Endopodite : It arises from the inner side of the stipes and
consists of two parts- outer broad, hood-like galea and an
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5. Walking legs
There are three pairs of walking legs, one pair attached
ventrally to sternum of each of prothorax, mesothorax and
metathorax and called fore, mid- and hind legs, respectively.
all the legs are similar, and each consisting of a linear series of
9 segments or podomeres.
Leg is articulated with its thoracic segment by a stout flattened,
basal coxa, followed by a smaller triangular trochanter. The
latter is fused to a stout spiny femur, followed by a slender
spiny tibia, which is the longest segment of leg. finally, the
tarsus is made of 5 very small movable podomeres or
tarsomeres bearing fine hairs.
basal tarsomere is longer and called metatarsus while
terminal tarsomere is named pretarsus. Inner edges of first
four tarsomeres bear soft adhesive pads, the plantulae.
Pretarsus ends in two lateral claws and between them a
median, delicate hair-covered porous pad, the arolium or
pulvillus which prevents from slipping. all the legs are used
for walking, running and climbing.
Wings
Cockroach has two pairs of wings. One pair of wings are
attached dorso-laterally between tergum and pleuron of both
mesothorax and metathorax. In P. americana wings reach up
to the tip of abdomen in female, and a little beyond in male
cockroach.
Chitin thickens around tracheae to form nurvures or veins
that strengthen the wings.
(i) Forewings
Mesothoracic or forewings are heavily sclerotised. They are
narrow,dark opaque and leathery in texture.They are not used
in flight but serve to protect the hindwings at rest. Hence they
are known as elytra, wing covers or tegmina.
(ii) Hindwings
Metathoracic or hindwings are thin, membranous, transparent,
broad, delicate and used in flight. They are kept folded like
a fan under the tegmina, when at rest. Movements are due to
special muscles attached to wing bases and working at a very
high speed.
External genitalia
reproductive organs (such as testes and ovaries) concerned
with production and transmission of gametes (ova and sperms)
are collectively termed internal genitalia. While organs
involved in sexual dimorphism, mating and deposition of eggs
are known as external genitalia. In cockroach, these are
appendages of the terminal segments of abdomen. Anal cerci
and anal styles have already been described earlier.Whereas
gonapohyses shall be dealt with the reproductive system of
cockroach.
BODY WALL
body wall or integument consists of : cuticle (explained earlier),
hypodermis and basement membrane.
Hypodermis
Hypodermis (or epidermis) lies beneath cuticle which it
secretes. It is a highly organised epithelium made of a single
layer of columnar cells resting on a basement membrane
and anchored to it by hemidesmosomes. besides secreting
cuticle, hypodermis resorbs endocuticle before each moult or
ecdysis. Dermal glands found in hypodermis are concerned
with the production of cement layer and different kinds of
cuticle. They probably also secrete pheromones and some
hormones. Oenocytes appear between hypodermal cells
and probably secrete wax or lipids that is transmitted to the
surface of cuticle.
Basement membrane
a typical stout and continuous basement membrane bounds
the inner surface of hypodermis. It consists of an amorphous
granular material, probably a mucopolysaccharide.
COeLOm (BODY CAvITY)
The large perivisceral body cavity of cockroach, enclosing
alimentary canal and other viscera, is a haemocoel containing
blood. True coelom in cockroach is much reduced and
represented only by the cavities of gonads.
Fat body (corpora adiposa) is a soft whitish tissue which
surrounds the viscera. Most of its cells store fat, glycogen
and protein, and are termed trophocytes. Some cells store
nitrogenous waste (uric acid) and are called urate cells.
PhYsIOLOGY Of PerIPLAneTA
DIGesTIve sYsTem/DIGesTIOn
It includes the mouth parts (already described), a long
alimentary canal and a pair of salivary glands.
Alimentary canal
alimentary canal is a long and somewhat coiled tube of
uneven diameter and divisible into three regions : foregut,
midgut and hindgut. foregut and hindgut are ectodermal
and lined with a thin cuticle secreted by ectoderm whereas

6. midgut is endodermal, devoid of cuticular lining and capable
of absorbing digested food.
Foregut
Foregut or stomodaeum includes mouth cavity, pharynx,
oesophagus, crop and gizzard.
(i) Mouth cavity : Mouth cavity or preoral chamber
is a small, ill-defined space outside mouth, surrounded by
mouth parts. food is crushed and acted upon by the salivary
secretion or saliva in mouth cavity.
(ii) Mouth : True mouth is a small opening at the base of
preoral cavity and leads into pharynx.
(iii) Pharynx : Pharynx is short and tubular and its cuticular
lining is more folded posteriorly.
(iv) Oesophagus : from pharynx arises a long, straight,
narrow and laterally compressed tube, the oesophagus.
(v) Crop : Crop is large, thin-walled, pear-shaped sac, which
extends well up to the third or fourth abdominal segment. It
is the largest part of foregut. Its outer surface is covered by
a network of tracheae. Crop serves as a reservoir for storing
food.
(vi) Gizzard : Crop leads behind into a small, cone
shaped, muscular and thick-walled chamber, the gizzard
or proventriculus, which marks the end of foregut. In the
gizzard, the cuticular lining first form 6 plates with teeth to
grind the food, and then bears bristles to let only the well
crushed food to pass on.
Midgut
Midgut is the short and narrow tube-like middle part of
alimentary canal also known as ventriculus or mesenteron.
It is internally lined by glandular epithelium and forms the true
stomach serving mainly for digestion and absorption.
(i) Hepatic caeca : Opening into the anterior end of midgut
are 6 or 8 short, narrow, blindly ending hollow tubes, called
enteric or hepatic caeca.These are internally lined by epithelium
and secrete digestive enzymes.
(ii) Malpighian tubules : from the junction of midgut and
hindgut arise 100 to 150 very narrow, thread-like, yellow-
coloured blind tubules projecting freely into haemocoel. These
are called Malpighian tubules and are excretory in function.
Hindgut
Hindgut or proctodaeum is divided into three regions : ileum,
colon and rectum.
(i) Ileum : The mid-gut continues into the ileum. It is short
and relatively narrower. Its posterior end is characterised by
the possession of six tiny triangular lobes internally, bearing
spicules and acting as a sort of sphincter. The ileum passes
undigested food into the colon.
(ii) Colon : actually it is a dilation of ileum and is the
longest, relatively thicker and coiled part of hind gut. It
leads into the rectum.
(iii) Rectum : rectum is an oval or spindle-shaped sac
with external ridges alternating with internal longitudinal
thickenings called rectal pads or rectal papillae. These are
6 in number and also known as rectal glands. It helps in the
absorption of water. rectum opens to outside by anus.
Digestive glands
They are as follows:
Salivary glands : There are paired salivary glands lying
one on each side of the oesophagus and crop. each gland
has two glandular portions and a salivary reservoir or
receptacle.Thesecretionsecretedbytheglandularportion
is known as saliva which is stored in the receptacles. The
saliva contains amylase, chitinase and cellulase enzymes.
Hepatic caecae are lined by the glandular cells which
secretedigestivesecretioncontainingproteolytic,amylolytic
and lipolytic types of enzymes.
The mid-gut is lined by glandular epithelial cells which
secrete a digestive secretion containing enzymes.
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7. CIrCuLATOrY sYsTem
Cockroach has an open or lacunar circulatory system as blood,
also called haemolymph, flows freely within the body cavity or
haemocoel. There is a heart and aorta but no capillaries and
veins.
Haemocoel
body cavity of cockroach is
called haemocoel. Haemocoel
is divided by a dorsal and a
ventral diaphragm into three
sinuses: (i) dorsal pericardial, (ii)
middle pervisceral and (iii) ventral
perineural.
fan-shaped alary muscles are
present in the floor of pericardial
sinus in each segment. These are
connected to heart and dorsal
diaphragm by connective tissue.
Perivisceral sinus contains the alimentary canal and is
mostly occupied by a whitish mass of tissue or fat body which
consists of following cell types:
Trophocytes : store fat, glycogen and proteins.
Myocytes : Contain symbiotic bacteria that secrete
vitamins, amino acids and glycogen from glucose.
Oenocytes : Take part in intermediary matabolism at the
time of ecdysis.
Urate cells : absorb nitrogen waste from haemolymph,
synthesize uric acid and store it.
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Perineural sinus encloses the ventral nerve cord.
Heart
Heart lies mid-dorsally beneath the terga of thorax and
abdomen. It is a long narrow tube with anterior end open
and posterior end closed. It consists of 13 funnel shaped
chambers or segments, each communicating by a valvular
opening with the one in front of it. Hinder end of each chamber
has a pair of minute lateral openings, the ostia.
These allow flow of haemolymph from pericardial sinus into
heart only and not in a back gear. The anterior narrow and
tubular part of heart is called anterior aorta. It is without
ostia and forwards into the head sinus.
Haemolymph
The haemolymph or blood of cockroach consists of a clear
colourless plasma rich in amino acids, uric acid, and
numerous different types of cells, called haemocytes.
Haemolymph is devoid of respiratory pigment and hence does
not assist in respiration.
blood also consists of a non-reducing sugar agent, called
trachealose– a characteristic of insects.
Blood circulation
blood or haemolymph circulates by the contraction and
relaxation of heart assisted by the paired fan-shaped alary
muscles. Contraction of these muscles enlarges the pericardial
sinus so that blood flows into it from the underlying perivisceral
sinus. When the muscles relax, blood is forced through ostia
into the heart.
Table : Digestion in Periplaneta
Part of alimentary canal Chemical/Enzyme secretion etc. Types of food digested
1.
2.
3.
buccal chamber
Pharynx
Oesophagus
Saliva secreted by salivary gland is mixed
with food
(i) Zymase
(ii) Chitinase
(iii) Cellulase
Carbohydrates
4. Crop (principal site of digestion) Invertase, maltase and lactase
Trypsin, proteases and peptidases
(iii) Lipase
Carbohydrates
Proteins
fats
5. Gizzard (i) food is triturated
(ii) Pulvilli filter the food
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6. Midgut (larger particles pushed back
into crop)
Midgut enzyme continue their action Carbohydrates, fats and proteins
7. Midgut + hepatic caeca absorption excess nutrients deposited in fat body
8. rectum (hindgut) Water and salts absorbed by rectal
papillae, rest defecated as dry pellet via
anus.
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8. resPIrATOrY sYsTem
respiratory system is well developed in a cockroach in order to
compensate the poorly developed circulatory system. It consists
of tracheae, tracheoles and spiracles.
Tracheae
Haemocoel contains a network of elastic, closed and branching
air tubes or tracheae. There are three pairs of large, parallel,
longitudinal tracheal trunks, one dorsal, one ventral and one
lateral in position,which are connected together by transverse
commissures. The cuticular lining is spirally thickened forming
intima or taenidia which prevents the tracheal tubes from
collapsing.
Tracheoles
The ultimate finer branches of tracheae are called tracheoles
which come in contact with the individual body cells.
The elaborate tracheal system carries oxygen directly to all the
body cells.
Spiracles
The main tracheal trunks open to the
exterior on body surface through 10
pairs of segmentally arranged
apertures termed spiracles
or stigmata. Two pairs of
spiracles are thoracic, one
between pro and mesothorax
and the other between meso
and metathorax. Eight pairs
of spiracles are abdominal,
one pair in each of the first eight
abdominal segments. They are present laterally in the soft
cuticle between a terga and sterna.
Respiratory mechanism and gaseous exchange
alternate contraction and relaxation of the abdominal
muscles(tergo-sternalmuscles)causerhythmiccontraction
and expansion of abdomen. Such movements cause change
in diameter of tracheae and force air in and out of tracheal
tubes through spiracles. 1st
and 3rd
pairs of spiracles always
remain open while the remaining eight pairs open only during
inspiration.
Gaseous exchange occurs by simple diffusion between air in
tracheae and dissolved gases in blood or tracheolar fluid which
has been shown to rise and fall.
exCreTOrY sYsTem
It regulates the amounts of nitrogenous material, inorganic
salts and water in blood or haemolymph. The main structures
playing the role of excretion are : Malpighian tubules, fat
body cells, uricose glands and cuticle.
Malpighian tubules
These are fine, long unbranched, yellowish and blind tubules
lying freely in the haemolymph and are attached to the
alimentary canal at the extreme anterior end of hindgut.
each tubule is about 16 mm long and 0.5 mm in diameter and is
lined by glandular epithelium with a characteristic brush border.
a Malpighian tubule has two functional parts.Glandular cells
of distal secretory part extract nitrogenous wastes and
water from haemolymph forming a solution called urine. The
urine flows towards the proximal absorptive part of tubule
which reabsorbs certain salts, such as potassium bicarbonate,
and some water resulting in precipitation of uric acid.
More water is reabsorbed in colon and rectum so that more or
less solid uric acid is eliminated with faeces through anus. So,
cockroach is uricotelic.
Fat body cells
It consists of many different types of cells, but only urate
cells are associated with excretion. These cells accumulate,
produce and store uric acid and urate granules throughout
life. This mode of excretion is termed storage
excretion.
Uricose glands
The mushroom gland of male
cockroach possesses long,
blind tubules at its periphery,
called uricose glands or utriculi
majores. These tubules store
uric acid (storage excretion)
and discharge it over the
spermatophore during copulation.

9. Cuticle
Cuticle also acts as a site where nitrogenous waste material is
deposited and then eliminated with its shedding at each moult
or ecdysis.
nervOus sYsTem
Nervous system comprises the central, peripheral and
sympathetic or stomatogastric nervous system.
Central nervous system consists of brain and double
ganglionated ventral nerve cord. Peripheral nervous
system comprises nerves arising from brain and segmental
gangliaandsympatheticnervoussystem(=Stomatogastric)
comprises four ganglia and a retrocerebral complex.
Central nervous system (made of 6 fused ganglia)
brain consisting of (a) protocerebrum, (b) deuterocerebrum
and (c) tritocerebrum which fuse to form a bilobed mass called
supra-oesophageal ganglion. The 3 other ganglia fuse to
form the sub-oesophageal ganglia.
Ventral nerve cord originates from sub-oesophageal ganglion.
It bears 3 ganglia in thorax called pro-meso-, and meta-
thoracic ganglia and six abdominal ganglia of which the
last i.e., 6th is formed by the fusion of many ganglion.
Peripheral nervous system
The nerves,given off from ganglia to all parts of body,constitute
the peripheral nervous system.
Sympathetic nervous system
It comprises four ganglia and a retrocerebral complex.
The four ganglia are : Frontal ganglion, hypocerebral
ganglion, ingluvial ganglion and proventriculus ganglia.
Retrocerebral complex lies above hypocerebral ganglion.
It is made up of endocrine organs (a) corpora cardiaca-
secretes hormone that regulate peristalsis of gut and act as
cardiac accelerator, and (b) corpora allata- secretes juvenile
hormone which is involved in reproduction, metamorphosis etc.
The nervous system of cockroach is spread throughout the
body. The head holds a bit of a nervous system while the rest
is situated along the ventral (belly-side) part of its body. So,
now you understand that if the head of a cockroach is cut off,
it will still live for as long as one week.
sensOrY sYsTem
Periplaneta has a variety of sensilla which are sensitive
to touch, smell, taste, detection of deleterious chemicals,
sound, temperature, and light. each sensilla (1-6) contains
neuro-sensory cell, trichogen cell and tormogen cell.
These are:
Tactile sensilla (= touch = thigmoreceptor) are present
all over the body, and abundant on antenna, legs, anal
cerci, maxillary palps.
Thermoreceptors (= sensitive to temperature) are
present on antennae, maxillary, and labial palp.
Gustatory ( = taste) are present on maxillary and labial
palps.
Auditory (= sound) are present on ventral surface of anal
cerci.
Proprioceptors (pressure) are sensitive to pressure set up
in cuticle during feeding and movement.
Light or photoreceptors are simple and compound
eye.
Simple eye (= ocellus) is present at the base of each antennae,
consists of lens that facilitates collection/filtering of light. It
does not form image but help in discrimination between dark
and dim light.
Compound eyes are large, sessile, paired, bean-shaped,
black in colour present on either side of head.The outer convex
surface of eye is divided into 200 hexagonal areas called facets
(200 × 2 = 400). below the facet lie series of visual units
called ommatidium. Periplaneta has 2000 such units (Honey
bee has 5, 000 and dragon flies 50,000) which are similar in
structure and function. all facets of an eye together form its
cornea.
each ommatidium is composed of :
(i) Diopteric region-from cornea to extreme ends of cone
cells and
(ii) Receptor (= retinular region).
The diopteric region consists of :
Transparent cuticle that acts as lens.
Corneagen cells (two in number) which secrete retina.
Crystalline cone formed by 4 cone cells serving as
accessory lens.
With the help of several ommatidia, a cockroach can receive
several images of an object. This kind of vision is known as
mosaic vision with more sensitivity but less resolution, being
common during night (hence called nocturnal vision).
–
–
–
–
–
–
–
–
–

10. neurO-enDOCrIne sYsTem
Neurosecretory cell in the brain secretes brain hormone (bH)
that affect secretory activity of other endocrine glands and
several other physiological processes.
The corpora cardiaca and corpora allata are already discussed.
Prothoracic gland is located in thorax. It secretes a hormone
called ecdysone (= moulting hormone) which stimulates
metamorphic changes in a nymph. ecdysone has a antagonistic
action to JH.
rePrODuCTIve sYsTem
In Periplaneta sexes are separate and sexual dimorphism is
pronounced.
Male reproductive organs
1. Testes : paired, massive, extend from 3/4 abdominal
segment to 6th has 3-4 interconnected lobes each of
which is formed of sac-like lobules.
2. Vas deferens (= sperm duct) originate from either side
of testes and receive the sperm from testicular lobules.
3. Ejaculatory duct : elongated, contractile, formed by
the union of right and left vas deferens. It opens to the
outside by male genital aperture that lies ventral to
anus. It is lined internally by cuticle.
Accessory genital glands
1. Utricular = Mushroom gland :
Large, white in color, present at the junction of vas
deferens and ejaculatory duct. It is made up of sac-like
tubules of three types :
Long - utriculi majores
Small - utriculi breviores and
bulb - like seminal vesicles
•
•
•
2. Phallic = Conglobate gland :
Club-shaped, long flattened, sac-like lie beneath the
mushroom gland. It opens by a separate aperture which
lies in proximity with genital aperture. It secretes outer
layer of spermatophore.
Accessory external genitalia
1. Malegenitalapertureissurroundedbythreeasymmetrical
plates called gonapophysis (= phallomere-right, left
and ventral) which arise from the 9th sternum.
2. Right phallomere consists of two horizontal
opposing plates, a sickle-shaped hook and a serrated
lobe terminating in two prongs.
3. Left phallomere consists of four components.
Titillator with a terminal hook.
Pseudopenis with a broad hammer-like head.
asperate lobe near pseudopenis bearing the
opening of phallic gland.
accutobolus having a hook.
–
–
–
–
4. Ventral phallomere bears male genital pore. It lies
below right phallomere. Opening of ejaculatory duct
lies at its base in an intromittent muscular region, called
phallus or edegus.
Female reproductive organs
1. Ovaries : paired, elongated, one on each side of abdomen,
extend from abdominal segment 2 – 6. If consists of 8
ovarioles in each ovary. (8 + 8 = 16)
Ovarioles has 5 parts :
– Terminal filament
– Germarium
– Vitellarium
– egg chamber
– Pedicel and plug
2. Oviduct : The pedicel of all the 8 ovarioles/ovary join to
form a small, muscular oviduct of their side.
3. Vagina : The left and right oviduct unite to form vagina
which opens into genital pouch by a slit-like gonopore (on
8th abdominal sternite).
4. Genital pouch (= Gynantrium)
boat-shaped sternite of 7th abdominal segment forms its
floor and 8th and 9th form roof and sides. The pouch is
divided into (a) genital chamber and (b) oothecal chamber.
The 7th sternite has 2 large and oval apical lobes on its
posterior region.
Accessory glands/structure
1. Collaterial gland : a pair of much branched accessory
or collaterial glands lies behind and above the ovaries.
Secretion of two collaterial glands forms the hard egg-
case or ootheca around groups of eggs.
2. Spermathecae : a spermatheca or receptaculum sem-
inis, consisting of a left sac-like and a right filamentous
caecum, opens by a median aperture in the dorsal wall of
genitalpouchon9th
sternum,atthetipofasmallspermathecal
papilla.Inafertile female,spermatheca is found filled
with spermatozoa, received during copulation, from the
male.
External genitalia
external genitalia consists of ovipositor made of 3 pairs
of chitinous processes called gonapophyses (arising
from 8th and 9th sterna), that hang into oothecal
chamber and facilitate arranging of ova in the ootheca.
They also help in imparting the characteristic shape to
ootheca.
Table : Differences between male and female reproductive organs

11. Males are smaller, have a visible abdominal sclerite, pointed
hind end, undivided 7th sternite, paired anal styles on 9th
abdominal sternite and wings larger extending behind the
body.
Females are larger with seven, visible abdominal sternites,
blunt and boat-shaped hind end, wings smaller, 7th sternite
divided, anal styles are absent and wings are smaller. The
male and female reproductive organs are compared
as given in table (Refer previous page).
LIfe hIsTOrY
Copulation
Sexually mature male and female cockroach generally mate
during night from March to September. During copulation, the
male transfers its spermatozoa in the form of packets, called
spermatophores, directly into the genital pouch of female.
Fertilization and Development
fertilization of the egg occurs into vestibulum of genital
pouch. fertilized eggs become surrounded by the secretion of
collaterial glands, which hardens to form an egg case or
ootheca. This ootheca is then laid in a warm, sheltered and
dark place.
The egg undergoes spiral cleavage. The young cockroaches
or nymphs emerge out leaving the egg membrane behind.
freshly hatched nymphs are delicate, transparent and almost
colourless.They possess nearly all adult characters but differ in
size and colouration, in being sexually immature and lacking
wings.
Metamorphosis
Immediately after hatching, the nymphs undergo first moulting
or ecdysis and then 6 or 7 successive moults follow.as nymphal
development proceeds, the wing pads arise, body increases
in size, colouration becomes darker and ultimately the adult
takes its form with fully developed wings and genitalia. Thus
development of cockroach is simple and direct and includes
incomplete or gradual metamorphosis which is known as
paurometaboly.
InTerACTIOn WITh mAnkInD
all the species of cockroach are harmful because they
contaminate food with their excreta, spread foul smell, and
also pose potential harm by acting as disease transmitting
agents. besides, cockroaches are the fourth most common
allergen. These also have a psychological impact on humans,
causing anxiety and stress due to embarrassment and physical
invasion.
neW mCQs
1. In cockroach, wings are absent from
(a) prothorax (b) mesothorax
(c) metathorax (d) none of these.
2. Number of spiracle pairs in Periplaneta americana is
(a) 8 (b) 9
(c) 10 (d) 11.
3. Male cockroach can be distinguished from female cockroach
through
(a) longer antennae (b) longer abdomen
(c) wingless body (d) all of these.

12. 4. Cockroach blood does not contain respiratory pigment. It
means
(a) it does not respire
(b) cockroach respires anaerobically
(c) oxygen passes to all the tissues through alary muscles
(d) oxygen reaches tissue through tracheoles.
5. In cockroach the longest podomere is
(a) coxa (b) trochanter or femur
(c) tibia (d) tarsus.
6. In cockroach moulting is induced by secretion of
(a) prothoracic gland (b) corpora allata
(c) corpora cardiaca (d) neurosecretory cells.
7. Spiracles of cockroach which are larger and always kept
open are
(a) first and second pairs (b) first and third pairs
(c) first and tenth pairs (d) second and third pairs.
8. antennae of cockroach have
(a) gustatory receptors (b) auditory receptors
(c) tactile receptors
(d) tactile and olfactory receptors.
9. Heart of cockroach is
(a) myogenic (b) neuromyogenic
(c) neurogenic (d) none of these.
10. Diagram represents posterior region of male cockroach.
Choose the correct combination of labelling
(a) 1 - 9th sternum, 2 - anal style, 3 - 10th tergum,
4 - anal circus
(b) 1 - anal style, 2 - anal circus, 3 - 10th tergum,
4 - 9th sternum
(c) 1 - 9th sternum, 2 - anal circus, 3 - 10th tergum,
4 - anal style
(d) 1 - 9th sternum, 2 - anal style, 3 - 10th tergum,
4 - anal circus
N
1. Ommatidia serve the purpose of photoreception in
(a) cockroach (b) frog
(c) humans (d) sunflower. (CbSe-2003)
2. excretion in cockroach takes place by
(a) nephridium (b) parotid gland
(c) coxal glands (d) Malpighian tubules.
(aIIMS-2002)
3. In cockroach,larval and nymphal characters are maintained
by
(a) ecdysone (b) salivary glands
(c) parotid gland (d) juvenile hormone.
(bHu-2006)
4. Which one of the following is the correct statement about
the circulatory system of cockroach?
(a) It is closed type of circulatory system.
(b) It is complicated type of circulatory system.
(c) It takes place without the participation of tissue.
(d) It has 13-chambered heart and in each segment one
pair of ostia are present.
(bHu-2007; DPMT-1998; uP-CPMT- 1996)
5. What is the main difference between male and female
cockroach?
(a) jointed appendages (b) paired antennae
(c) anal cerci (d) conglobate gland.
(bHu- 2008)
6. In cockroach, the ootheca is formed by the secretion of
(a) phallic gland (b) collaterial gland
(c) mushroom gland (d) conglobate gland.
(DPMT-1995,1996; Manipal-2002, 2004)
7. In cockroach, oxygen is transported by
(a) trachea (b) plasma
(c) haemoglobin (d) histamine. (DPMT-1998)
8. The difference between male and female cockroach is
(a) in male anal cerci are present
(b) in male anal style are present
(c) in female anal style are present
(d) in female and cerci are present. (uP-CPMT-1996)
9. Phallic organs in cockroach are related to
(a) male excretory system
(b) male reproductive system
(c) female excretory system
(d) female reproductive system. (uP-CPMT-1998)
10. The cockroach of genus Blatta is also called
(a) German cockroach (b) australian cockroach
(c) Oriental cockroach (d) american cockroach.
(uP-CPMT-2004)
11. Stink gland is found in
(a) 4th
and 5th
terga of cockroach
(b) 5th
and 6th
terga of cockroach
(c) 5th
and 6th
sterna of cockroach
(d) 4th
and 5th
sterna of cockroach. (uP-CPMT-2007)
12. Cockroach mainly excretes
(a) uric acid (b) urea
(c) ammonia (d) amino acid
(uP-CPMT-2009)
13. Heart of cockroach is
(a) 13 – chambered (b) 29 – chambered
(c) 9 – chambered (d) 6 – chambered
(uP-CPMT-2009)

13. 14. Conglobate gland is found in
(a) female cockroach (b) male cockroach
(c) Anopheles mosquito (d) Culex mosquito.
(Manipal-2005)
15. Which structure is absent in male cockroach ?
(a) seminal vesicle (b) phallomeres
(c) spermatheca (d) none of these.
(aMu-2006)
16. In the nymphal stage of cockroach the juvenile hormone is
secreted by
(a) corpora cardiaca (b) corpora allata
(c) prothoracic gland (d) intercerebral gland cells
(aMu-2009)
17. earthworm and cockroach have which of the following thing
in common ?
(a) nephridia (b) ventral nerve cord
(c) cocoon
(d) closed blood vascular system. (afMC-1995)
18. In the following diagram of a leg of cockroach parts have
been indicated by alphabets. Choose the answer in which
these alphabets have been correctly matched with the parts
which they indicate
(a) a = coxa, b = tibia, c = tarsus,
d = femur, e = trochanter
(b) a = coxa, b = femur, c = trochanter,
d = tarsus, e = tibia
(c) a = coxa, b = tarsus, c = femur,
d = tibia, e = trochanter
(d) a = coxa, b = trochanter,
c = femur, d = tibia, e = tarsus. (Karnataka-2003)
19. The young one of cockroach is called
(a) caterpillar (b) nymph
(c) fingerling (d) maggot. (Karnataka-2004)
20. Which of the following happens in the common
cockroach?
(a) Malpighian tubules are excretory organs projecting
out from the colon.
(b) Oxygen is transported by haemoglobin in blood.
(c) Nitrogenous excretory product is urea.
(d) The food is ground by mandibles and gizzard.
(aIPMT Prelims-2011)
21. about how many times does the nymph of the Periplaneta
americana undergo moulting before becoming an adult?
(a) 4 (b) 2
(c) 17 (d) 3
(e) 7 (Kerala-2011)
22. Compound eyes are found in
(a) frog (b) earthworm
(c) cockroach (d) roundworm. (aMu-2011)
23. The head of cockroach lacks
(a) cardo (b) gena
(c) trochanter (d) frons. (uP-CPMT-2011)
24. Mushroom gland is a part of
(a) male reproductive system of cockroach
(b) female reproductive system of cockroach
(c) male reproductive system of rabbit
(d) female reproductive system of rabbit.
(uP-CPMT 2010)
25. In the mouth parts of cockroach,the galea and lacinia form
parts of the
(a) mandible (b) maxilla
(c) labium (d) labrum (aMu-2010)
26. Cockroaches can climb smooth or steep surfaces due to
the presence of adhesive pads found on the torses of their
legs.They are called
(a) plantulae (b) tibia
(c) pretarsus (d) arolium (Karnataka-2010)
27. The respiratory pigment present in cockroach is
(a) vanadium (b) haemocyanin
(c) malpadin (d) none of these
(Orissa-2010)
N
The following questions consist of two statements each :
assertion (a) and reason (r). To answer these questions, mark
the correct alternative as directed below :
(a) If both a and r are true and r is the correct explanation
of a.
(b) If botha and r are true but r is not the correct explanation
of a.
(c) If a is true but r is false.
(d) If both a and r are false.
1. Assertion (A) : Haemocoel in Periplaneta is not lined
by the mesodermal epithelium.
Reason (R) : Periplaneta possess highly developed true
coelom.
2. Assertion (A) : The development of P. americana is
paurometabolus.
Reason (R) : In them development occurs through
nymphal stage.

14. 3. Assertion (A) : In cockroach Malpighian tubules help
in excretion.
Reason (R) : It is present at the juction of midgut and
hind gut.
4. Assertion (A) : blood vascular system of cockroach is
of closed type.
Reason (R) : blood vessels are well developed and
open into space called haemocoel.
5. Assertion (A) : Cockroaches are dioecious.
Reason (R) : Male reproductive system and female
reproductive system are found in the 6th
- 7th
abdominal
segments.
NS
1. fill in the blanks.
(i) all the legs of cockroach are similar,and each consists
of linear series of nine segments of _________ .
(ii) The excretory product of cockroach is _________ .
(iii) The accessory genital glands of male cockroach is
called _________ .
(iv) In cockroach _________ serves as a reservoir for
storing food.
(v) The blood of cockroach circulates by the contraction
and relaxation of heart which is assisted by the paired
fan-shaped _________ .
2. What do you call the circulatory fluid in the body of
cockroach? Mention its three functions.
3. Name the excretory organ of cockroach.
4. Name the mouth parts of cockroach.
5. (i) What is the name of tracheal opening in cockroach ?
(ii) How many segments are present in the abdomen of
cockroach ?
(iii) Where do you find Malpighian tubules in cockroach?
6. Mention three differences between male and female
cockroach.
7. refer the following figure and answer the given questions.
(i) Identify a, b, C and D.
(ii) What does this figure represent?
(iii) Which labelled part is formed of a group of eight
ovarian tubules or ovarioles, containing a chain of
developing ova?
(iv) The labelled part b is present in which abdominal
segment?
ERS
Part - I
1. (a) 2. (c) 3. (b) 4. (d) 5. (c)
6. (a) 7. (b) 8. (d) 9. (c) 10. (c)
Part - II
1. (a) 2. (d) 3. (d) 4. (d) 5. (d)
6. (b) 7. (a) 8. (b) 9. (b) 10. (c)
11. (b) 12. (a) 13. (a) 14. (b) 15. (c)
16. (b) 17. (b) 18. (d) 19. (b) 20. (d)
21. (e) 22. (c) 23. (c) 24. (a) 25. (b)
26. (a) 27. (d)
Part - III
1. (c) 2. (a) 3. (b) 4. (d) 5. (c)
Part - IV
1. (i) podomeres (ii) uric acid
(iii) mushroom gland (iv) crop
(v) alary muscles
2. The circulatory fluid of cockroach is colourless haemolymph
which fills the entire haemocoel. It helps in (i) transportation
of nutrients, (ii) maintains hydrostatic pressure and (iii) acts
as a reservoir of water.
3. Malpighian tubule.
4. Mouth parts of cockroach are head appendages surrounding
the mouth. These consist of the labrum or upper lip, a pair
of mandibles, a pair of maxillae, the labium or lower lip
and the hypopharynx.
5. (i) It is called spiracle.
(ii) In the embryo the abdomen consists of eleven segments
but in the adult form it comprises ten segments.
(iii)Malpighian tubules are found attached at the junction of
mid and hindgut.
6. The three differences between made and female cockroach
is given below:
Male cockroach Female cockroach
(i) abdomen is relatively (i) abdomen is relatively
long and narrow. short and broad.
(ii) Ninth abdominal sternum (ii) There are no anal styles.
bears a pair of anal styles.
(iii) There are only three (iii) There are three pairs of
gonapophyses. gonapophyses.
7. (i) a = Ovary b = Spermatheca,
C = Gonapophyses, D = Collaterial glands.
(ii) The figure represents the reproductive system of
female cockroach.
(iii) a = Ovary
(iv) The labelled part b (spermatheca) is present in 6th
segment which opens into the genital chamber.
nn

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