Long Answer Type Questions

1. Describe the structure of the head of a cockroach, with the help of a neat labelled diagram.

A: The head of the cockroach is slightly triangular in shape and called hypo gnathus, as it is bent towards right angle to the body axis with mouthparts directed downwards.

* Head is formed by fusion of six anterior embryonic segments.

* The top of the head between the eyes is called vertex, which is covered by a pair of epicranial plates connected by suture. Covering the head below vertex is frons sclerite and below it a small triangular clypeus sclerite to which labrum is connected. On the sides of eyes, a pair of cheek genae sclerites is present.

* At the back of the head capsule, there is a large opening called occipital foramen, connecting the cavity in the neck, and through which oesophagus, nerve cord, aorta and tracheae pass.

* A pair of whitish spots is present at the base of antennae, called fenestrae or ocelli or simple eyes.

* I and III segments of the head do not have any appendages, but II, IV, V and VI segments bear a pair of antennae, a pair of mandibles, a pair of first maxillae, and II maxillae (labium) respectively.

* Mouth parts of Cockroach are biting and chewing type, and consist of 5 parts, i.e. a labrum, a pair of mandibles, a pair of first maxillae, a pair of second maxillae and a hypopharynx, surrounding pre-oral cavity.

* Labrum is a renicircular, flat plate connected to clypius sclerite, containing olfactory receptors and help in holding the food during ingestion. 

* A pair of mandibles with teeth is present are on either side of pre-oral cavity, attached to the genae and help in mastication.

* A pair of first maxillae is present one on either side of mouth just below the mandibles. Each maxilla is biramous and made up of 3 parts, i.e., protopodite, exopodite, and endopodite. Protopodite is formed by cardo and stipes, on which exopodite (maxillary palp) and endopodite (Lacinia and galea) are present. First maxillae are used to clean antennae and first pair of legs and bring the food to mandibles.

* Second pair of maxillae are fused to form single, broad plate like labium or lower lip, below first pair of maxillae. It is formed of 3 parts- submentum, mentum and prementum. A pair each of labial palps, paraglossae and glossae are present on prementum. Labium prevents the food from falling while ingestion.

* Hypopharynx is small, rod-like, groobed, chitinous mouth part and also called tongue or lingua. It is present between first pair of maxillae in the pre- oral cavity, contains opening of efferent salivary duct.

2. Describe the abdomen of cockroach.

A: The abdomen of the cockroach contains 10 segments. Each segment is enclosed by a dorsal tergum, a ventral sternum, and a pair of pleural sclerites.

* Abdomen is the largest and third tegmata in the body of the cockroach.

* Both male and female cockroaches do not have 10th sternum and from 10th tergum a pair of jointed anal cerci arise. In males, a pair of unjointed anal styles arises from 9thsternum.

* 8th tergum in males and 8th and 9th terga in females are not visible as they are overlapped by the 7th tergum.

* 10th tergum in both sexes extend posteriorly beyond the body and has a deep groove at free, distal end.

* In males, all nine sterna are visible, whereas in females, only 7 sterna are visible due to presence of brood pouch, which is formed by 7th, 8th and 9th sterna.

* In females, 7th, 8th and 9th sterna make brood pouch, which has two chambers - Anterior gynatrium or  genital chamber and posterior oothecal chamber.

* Gonapophyses are external reproductive organs and are flat, chitinous processes, surrounding genital apertures in both sexes. Male gonapophyses are called phallomeres and are 3 in number - left, right and ventral phallomeres and they participate in copulation. Female has 3 pairs of gonapophyses and these are ovipositor organs. In males, gonapophyses are appendages of 9th segment and in females, these are appendages of 8th and 9th segments.

* At posterior end of the body, alimentary canal opens through anus, which is surrounded by 4 podical plates.

* In males, the genital aperture opens just below anus between 9th and 10th segments. In females, the genital aperture opens on 8th sternum.

* Abdomen also contains 8 pairs of spirales in first 8 segments that are located on pleura.

* Between 5th and 6th segments, 2 pairs of small split pouches are present and they are called stink glands as they secrete characteristic substance that cause the females to attract and participate in copulation.

3. Describe the digestive system of cockroach with the help of a neat labelled diagram.

A: Digestive system of the Cockroach consists of two parts- Alimentary canal and Digestive glands, that are associated with alimentary canal.

* Infront of the mouth, preoral cavity is present, which is surrounded by mouthparts and it is divided by two chambers by hypopharynx anterior cibarium and posterior salivarium, into which the salivary glands open.

ALIMENTARY CANAL:

* Alimentary canal is a long, tubular structure, which is longer than the length of the body, hence it is coiled. It is extended between mouth in the anteriorend and anus in the posteriorend.
* Alimentary canal contains three parts, i.e., foregut (stomodaeum), midgut (mesenteron) and hindgut (proctodaeum). Stomodaeum and proctodaeum are internally lined by chitinous layer derived from ectoderm and mesenteron is internally lined by glandular epithelium derived from endoderm.
* Foregut includes mouth, pharynx, oesophagus crop and gizzard. Mouth leads to pharynx which leads to narrow, tubular oesophagus, which opens into a thin walled, elongated crop. Crop is used for temporary storage of food. Crop opens into thick walled, muscular round, bulb-like gizzard or proventricus.
* The gizzard can be divided into anterior armarium and posterior stomadaeal valve. The cuticular lining of gizzard thickens to form six chitinized teeth, and behind them cushion - like pads covered with bristles. The teeth help in grainding the food, white bristles help in straining the food.
* The hind part of gizzard projects into midgut as a funnel, called stomodaeal valve, which prevents regurgitation.
* The gizzard is followed by a narrow, short tube, called mesenteron or ventricules.  Arising from mesenteron at the junction with gizzard eight finger-like, tubular, blind processes called hepatic or enteric or mesenteron caecae, which are helpful, in digestion and absorption.
* Mesenteron can be functionally divided into anterior secretory and posterior absorptive parts.
* The internal lining of mesenteron is covered by very thin layer of transparent peritrophic membrane, which is produced by stomodeal valve. This membrane protects the wall from sharp objects may be present in the food.
* Digestion and absorption of digested food are completed in midgut.
* Undigested food enters hindgut, which includes 3 parts - ileum, colon, and rectum. The opening of midgut into hindgut is regulated by a sphincter muscle, which prevents the undigested food to reenter into midgut.
* Ileum following midgut is a short, narrow tube. The junction of midgut and hindgut is marked by the presence of nearly 60 - 150 long filamentous, yellow coloured and blind malpighian tubules, which are excretory organs.
* Ileum opens into colon, which ends in a broad rectum, which opens by an anus lying posteriorly below the 10th tergum.
* Inner lining of colon is wrinkled and that of the rectum forms six thick longitudinal folds, called rectal papillae, which are considered with reabsorption of water from the undigested food.
 

DIGESTIVE GLANDS:
*  Digestive glands of Cockroach include salivary glands, hepatic caecae, and glandular cells of mesenteron.
* Apair of salivary glands, attached to ventro - lateral sides of the crop in the thorax, contaning each gland has two glandular portions and bag like reservoir. From salivary portions of both, sides a pair of salivary ducts arise and unite to form a common duct of salivary glands or median salivary duct.
*  From each reservior, a recepticular duct arises and both ducts unite to form a common duct of reservoir. Two common ducts join to form an efferent salivary duct, which opens in the preoral cavity, at the base of hypopharynx.

* Each salivary gland is made up of several secreting lobules, called acini. Each acinus is formed of zymogen cells, and a short ductule.
* Hepatic caecae contain secretory and absorptive cells.
* The glangular cells of mesenteron secrete digestive enzymes - saccharidases, proteases and lipase.
 

4. Describe the blood circulatory system of Periplaneta in detail and draw a neat and labelled diagram of it.
A: Blood circulatory system of the cockroach is open or lacunar type as it does not have blood vessels, except dorsal aorta, hence it is poorly developed.
* Since lack of blood vessels, blood comes in direct contact with tissues, and the rate of blood flow is low, hence the viscera is directly bathed with blood.
* Blood circulatory system includes 3 parts.
1) Haemocoel
2) Heart
3) Blood or haemolymph.
 

Haemocoel:
* The body cavity of the cockroach is filled with blood, hence it is called haemocoel, which is divided into three large spaces, called sinuses by two muscular, membranous septa or diaphragms.
* These three sinuses are known as dorsal sinus or pericardial sinus enclosing the heart, middle sinus or perivisceral sinus enclosing the viscera and ventral sinus or perineural sinus enclosing ventral nerve cord. Perivisceral sinus is the largest.
* Two membranous septa are known as dorsal diaphragm and ventral diaphragm, and there are perforated, allowing all sinuses to communicate with one another.
* There are 12 pairs of alary muscles extending between terga and the heart and are arranged segmentally. Each alary muscle is triangular in shape and broad end is attached to dorsal septum and pointed end is attached to the tergum. Regular, alternate, rhythmic contraction and relaxation of alary muscles cause pulling of dorsal septum and increasing the volume of pericardial sinus, allowing the flow of blood into the heart, from dorsal sinus.

 

Heart:
* Heart of the cockroach is elongated tube with muscular wall and segmentally arranged funnel-shaped, containing 13 chambers.
* It is located mid dorsally below the terga. Each chamber of the heart is roughly triangular in nature and anteriorly opens into chamber infront of it and posteriorly having two openings with valves called ostia, which allow flow of blood from dorsal sinus into the heart. Since the heart is pulsatile the blood in the heart flows forward, towards the head.
* First chamber of the heart opens into haemocoel of the head by dorsal aorta as the last chamber is closed at posterior end.
 

Blood (Haemolymph):
* Blood of cockroach is colourless as it does not have respiratory pigment. Blood does not participate in transportation of respiratory gases. Blood is formed of plasma and haemocytes, which are phasocytes. Plasma contains water, inorganic and organic substances.
* Blood performs several vital functions, such as transportation of food, nitorgenous wastes, hormones etc., and defend the body from micro organisms as phagocytes engulf pathogens.
 

5. The blood circulatory system of Periplaneta is of open type. Illustrate the statement describing the course of circulation in it.
A: Blood circulatory system of the cockroach is open type, in which blood flows through spaces of the body called sinus as blood vessels are absent.
* During embryonic development, the blood vessels enlarge themselves and form blood sinuses in which the blood comes in contact with tissues directly and viscera is bathed in the pool of blood.
* Wave of contraction in the wall of heart sets from posterior end to anterior end, forces the blood to enter into dorsal aorta, from which blood flows into head sinus.
* From the head sinus, the blood flows into perivisceral and perineural sinuses. When alary muscles contract the dorsal septum would be pulled downwards, results in the volume of pericardial sinus to be increased and forcing the blood to enter the dorsal sinus, from perivisceral sinus through perforations of dorsal septum, simultaneously the ostia open then blood enters the chambers of the heart, upon relaxation of alary muscles, and the ostia are closed.

 

6. Describe the respiratory system of cockroach with the help of neat and labelled diagrams.
A: Respiratory system of the cockroach consists of network of air-tubes that transport gases between atmosphere and tissue cells, called tracheal system, which is well developed and compensates absence of respiratory pigment in the blood.
* Respiratory system is formed by spiracles, tracheae and tracheoles.

Spiracles or Stigmata:
* Tracheal system opens exterior through serially arranged 10 pairs of openings, called spiracles. Two pairs are located in the thorax and eight pairs are located in the abdomen. These are situated in the pleura of their respective segments.
* Each spiracle is valvular and supplied with bristles or hair called trichomes to prevent the entry of dust particles and surrounded by single annular chitinous ring called peritreme.
* Each spiracle opens into a small chamber behind called atrium.
* The spiracles are described as polypneustic, because there are more than 3 pairs of spiracles and holopneustic, because all of them are functional.
 Tracheae:
* Tracheae are respiratory - air tubes, that are scattered throughout the body.
* From each atrium of thoracic spiracle, several tracheal tubes arise and anastomose with one another to form tracheal trunks - Dorsal, ventral and lateral cephalic. The branches of these enter all organs of the head, and thorax.
* From each atrium of the spiracles, 3 tracheal tubes arise. All of these tubes open into 3 longitudinal tracheal trunks - lateral, dorsal and ventral on each side. Tracheal trunks on both sides join by transverse commissural tracheae. Several branches formed from tracheal trunks enter different organs in the abdomen. All tracheal branches before entering into organs end in a special cell called tracheole cell.
* The wall of trachea contains 3 layers i.e. outer basement membrane, middle single cell thickness epithelium and inner cuticular intima, which has spiral thickenings along called taenidia which prevents collapsing of trachea when air is absent.
Tracheoles:
* The fine branches of trachea, which are intracellular, tubular extensions of tracheole cell are called tracheoles.
* These are very minute and thin with single protein layer called trachein in the wall and devoid of intima and taenidia.
* Tracheoles penetrate the cell and are functionally associated with mitochondria.
* Tracheoles contain tracheolar fluid and the level of this fluid differs based on physiological activities of the insect. O2 dissolves in the fluid and diffuses into the cell during respiration.

 

7. Describe the nervous system of Periplaneta and draw a labelled diagram of it.
A: Nervous system of the cockraoch consists of 3 parts.
1. Central nervous system
2. Peripheral nervous system
3. Autonomic nervous system.
1. Central nervous system (CNS) is formed by 2 parts
                     Nerve ring and                      
                     Ventral nerve cord.
* Nerve ring is present around the oesophagus in the head capsule and formed by supra - oesophageal ganglion, sub - oesophageal ganglion, and circum - oesophageal connectives.
* Supra - oesophageal ganglion also called Brain or cerebral ganglion is present on the top of oesophagus in the head, and formed by 3 parts.
   1. Protocerebrum
   2. Deutocerebrum
   3. Tritocerebrum
Brain is the centre of sensory and endocrine activities. Three pairs of sensory nerves, called optic, antennary and labrum from the eyes, antennal, and labrum connected with brain.
* Sub-oesophageal ganglion is present below the oesophagus in the head, and formed by fusion of 3 pairs of ganglia called mandibular, maxillary and labial. It is centre for motor activities that regulate the movements of mouth parts, legs and wings.
* A pair of circum - oesophageal connectives connects the brain with suboesophageal ganglion.
* Ventral nerve cord is solid, double, ganglionated, segmental, ventral in position that arises from sub-oesophageal ganglion and runs backwards towards posterior end of the body then extends upto 7th abdominal segment.
* Ventral nerve cord contains 9 segmental ganglia- three are present in thorax and six are present in the abdomen of the body. Three thoracic ganglia are present, one in each thoracic segment, called prothoracic ganglion, mesothoracic ganglion, and metathoracic ganglion and six abdominal ganglia are present, one in each segment of 1st, 2nd, 3rd, 4th, 6th and 7th abdominal segments (5th, 8th 9th and 10th abdominal segments are devoid of segmental ganglia).
  6th abdominal ganglion is the last and largest of all segmental ganglia as it is formed by fusion of 7th, 8th, 9th and 10th abdominal ganglia.

2. Peripheral nervous system contains all the nerves of central nervous system. Three pairs of nerves, called optic, antennary and labro-frontal, arise from the brain and mouth parts, legs and wings are innervated with motor nerves from sub-oesophageal ganglion.
* Thoracic ganglia give off nerves to the organs of respective sigments, and the organs of first abdominal segment receive nerves from metathoracic ganglion. 2nd, 3rd, 4th, 5th abdominal segmental organs are innervated by 1st, 2nd, 3rd, 4th adbominal ganglia, but 6th abdominal segmental organs are innervated with 5th abdominal ganglion and 7th, 8th, 9th and 10th abdominal segmental organs are innervated with nerves from 6th abdominal ganglion.
3. Autonomic nervous system (ANS) contains sympathetic ganglia and their connectives. ANS regulates the functions of visceral organs, hence also called 'visceral nervous system' or 'stamatogastric Nervous System' or 'sympathetic nervous  system'.
* ANS includes 4 ganglia i.e. frontal, hypocerebral, visceral, and proventricular  and their connectives. Frontal ganglion lies above the pharynx, in front of the brain. It is connected with the brain by frontal connective of the labro - frontal nerve.
Hypocerebral or occipital ganglion lies on the oesophagus behind the brain and is connected by a connective called median recurrent from frontal ganglion viseral ganglion or ingluvial lies on the crop and is connected by median connective from hypocerebral ganglion. Proventricular ganglion is connected by a connective nerve from visceral ganglion.
 

8. Describe the reproductive system of Periplaneta and draw neat and labelled diagrams of it.
A: Male reproductive system
* Male reproductive system of the cockroach includes 1 pair of testes, 1 pair of vasa deferentia, an ejaculatory duct a mushroom gland, seminal vesicles, a phallic gland, a genital pouch and three phallomeres.
* 1 pair of testes lies are on either dorso - 1 lateral side of 4th to 6th abdominal segments. They produce spermatozoa.
* A pair of vasa deferentia one from each testes arises, and run posteriorly downwards to open the ejaculatory duct. They transport spermatazoa.
* Ejaculatory duct is single, median, and muscular duct that opens into genital pouch through male genital pore.

* The junction of two vasa deferentia and ejaculatory duct, is surrounded by an elaborate mushroom gland consisting of numerous, compact, finger-like blind tubules, (large, peripheral tubules are called utriculi majores and short, central tubules are called utriculi breviores.)
* Present on the ventral surface of anterior part of ejaculatory duct are two groups of white sacs constituting seminal vesicles meant for storage of sperms.
* A club-shaped gland, called phallic or conglobate gland is present below the ejaculatory duct in the 5th abdominal segment. Its duct also opens into the genital pouch by the side of male genital pore. This gland secretes the outer layer or spermatophore.
* Male genital pouch lies at the end of abdomen, into which male genital pore, duct of phallic gland, and anus open.

Female reproductive system of the Cockroach consists of
1. a pair of ovaries 
2. a pair of oviducts
3. a common oviduct (vagina)
4. female genital pore
5. a pair of spermathecae
6. spermthecal papilla
7. a pair of collateral glands
8. three pairs of gonapophyses
* There are a pair of ovaries, lying between 2nd and 6th abdominal segments. Each ovary is made up of 8 ovarian tubules or ovarioles each ovariole is tapering at anterior end (germarium) and under at posterior end (vitellarium). All eight ovarioles at the posterior end unite with one another to form an oviduct.
* Both the oviducts unite and constitute a common oviduct or vogina, which opens into genital chamber by female genital aperture, on 8th sternum.
* Apair of spermthecae of unequal size unite to form a short common duct, which opens into genital chamber, near female genital aperture on a small spermathecal papilla.
* A pair of highly branched collaterial glands, lies behind and above the ovaries. These open into genital chamber separately.
* Genital pouch is formed by 7th, 8th and 9th sterna and contains female genital aperture, spermthecal opening, and openings of collateral glands.
* Female gonopore is surrounded by three symmetrically arranged, plate-like, chitinous processes, which are called gonopophyses or female external genitalia, which are oripositor organs.
 

Very Short Answer Type Questions

1. Why do you call cockroach a pest?
A. Cockroach is a domestic/ household pest, that contaminates our food sources with its excreta and pathogens. It can also transmit many disease causing microbes through contamination. It may cause damage to crops, food, and livestock.
 

2. Name the terga of thoracic segments of cockroach.
A. The terga of thorax are called pronotum, mesonotum and metanotum. Pronotum is the largest and covers neck and head partially on dorsal surface.
 

3. What are the structures with which cockroach walks on smooth surfaces and on rough surfaces respectively?
A. The claws and arolium or pulvillus help in locomotion on rough surfaces, where as plantulae help in locomotion on smooth surfaces.
 

4. Name the chitinous tubes that support the wings of  cockroach.
A. Hallow tubes network in the wings are called veins or nervures and their arrangement has taxonomical importance.
 

5. What is tegmen? What is its function?
A. The forewings of the cockroach are small, thick, opaque and leathery, are called tegmina which cover and prorect hind wings at rest.
 

6. Why is the head in cockroach called hypognathous?
A. The head of cockroach is described as hypognathous because it lies hanging at right angles to the body making mouthparts directed down word.
 

7. How is tripod formed with reference to locomotion in cockroach?
A. During locomotion three pairs of legs form two tripods with one foreleg and hindleg on one side along with middleleg on other side.
 

8. Name the muscles that help in elevating and depressing the wings of a cockroach.
A. The wings of the cockroach are elevated by contraction of dorso-ventral muscles and depressed by cotraction of dorso-lateral muscles.
 

9. Name the different blood sinuses in cockroach.
A. Haemocoel of the cockroach has three blood sinuses, viz, pericardial sinus, surrounding the heart, and perivisceral sinus, surrounding viscera and perineural sinus, surrounding ventral nerve cord.
 

10. How are the fat bodies similar to the liver of the vertebrates?
A. The fat bodies of the cockroach are analogous to liver of vertebrates, both organs store glycogen, produce nitrogenous waste materials etc.
 

11. What are the three regions of the alimentary canal in cockroach?
A. Alimentary canal of the cockroach is a long, coiled tube extending between mouth and anus and is divided into three parts, viz, foregut (stomodaeum) midgut (mesenteron) and hindgut (proctodaeum).
 

12. How many denticulate plates are present in the gizzard of cockroach?
A. Gizzard or proventriculus of the cockroach has six powerful denticulate plates of teeth for pulvarizing the food into small particles like grinding machine.
 

13. Which part of the gut secretes the peritrophic membrane in cockroach?
A. Chitinous, porous peritrophic membrane is secreted by stomodeal valve of    proventriculus around the food bolus to protect the wall of mesenteron.
 

14. Which parts of cockroach help in locating the food?
A. Olfactory sensory receptors or sensillae on the antenna help to locate the presence of food.
 

15. In which part of the gut of cockroach, water is reabsorbed?
A. Rectum.
 

16. Write the names of mouthparts in cockroach that help in biting and tasting the food.
A. Solid food is masticated and chewed by the mandibles and gustatory sensillae (a type of  chemo receptors) present on the labrum maxillary palps and labial palps help in tasting the food.
 

17. What are alary muscles?
A. Alary muscles, 12 pairs in number, contract and relax rhythmically to raise and depress dorsal diaphragm result in flow of blood from perivisceral sinus to pericardial sinus and finally into the heart.
 

18. What is haemocoel?
A. The body cavity of the cockroach is called haemocoel because it is a part of circulatory system and is filled with blood.
 

19. The three sinuses in a cockroach are not equal in size. Why?
A. Haemocoel of the cockroach is divided into three sinuses viz., pericardial, perivisceral, and perineural sinuses by two muscular membranous septa, viz, dorsal and ventral diaphragms, and perivisceral sinus is the largest as it contains all visceral organs, comparing to other two sinuses, which provide spaces to heart by pericardial sinus and ventral nerve cord by perineural sinus.
 

20. Why is the blood of Periplaneta called haemolymph?
A. The blood of cockroach is called haemolymph because it does not contain respiratory pigment, haemoglobin and presence of colour less cells in plasma.
 

21. What is the function of haemocytes found in the blood of Periplaneta?
A. Haemocytes in the blood of cockroach are blood corpuscles and perform phagocytic function.
 

22. Why does not the blood of Periplaneta help in respiration?
A. Blood of cockroach does not have respiratory pigment, hence it does not perform respiratory role.
 

23. Write important functions of blood in Periplaneta?
A. Important functions of blood of cockroach include:
1. Transportation of food
2. Transportation of  nitrogenous wastes to excretory organs
3. Transportation of phagocytes to infected areas of the body
4. Transportation of secretions of ductless(endocrine) glands to the target tissue cells.
 

24. The blood of Periplaneta is not red. Which pigment, do you think is absent in it?
A. The blood of cockroach is not red coloured, due to absence of respiratory pigment,  haemoglobin.
 

25. How many spiracles are present in cockroach? Mention their locations.
A. Tracheal system of the cockroach consists of ten pairs of spiracles; two pairs in thoracic segments and rest of them present in first eight abdominal segments. Spiracles are present in the pleura of their related segments.
 

26. What are trichomes? Write their functions.
A. All spiracle of the cockroach bear with small hair-like structures to prevent the entry of dust particles into the tracheae.
 

27. Why is the respiratory system of cockroach called polypneustic and holopneustic system?
A. The respiratory system of the cockroach is described as polypneustic because number of spiracles  is more than three pairs and holopneustic because they are all functional with respect to respiration.
 

28. Name the chitinous ring that encircles the spiracle of cockroach.
A. Each spiracle of the cockroach is surrounded by a circular chitinous ring-like structure called peritreme.
 

29. What are intima and taenidia?
A. The wall of trachea is made up of three layers, viz, outer basement membrane, middle epithelium with single cell thick and inner cuticle layer called intima. Spiral thickenings along length of tracheal wall called taenidia which prevent the tracheae from collapsing.
 

30. Name the protein that lines the tracheole of the cockroach.
A. The wall of tracheoles is devoid of intima and taenidia, rather formed of a protein called trachein.
 

31. During inspiration which spiracles are kept open and which are kept closed?
A. During inspiration the thoracic spiracles are kept open, while the abdominal spiracles are kept closed.
 

32. Which factors regulate the opening of the spiracles?
A. Spiracles open or close due to CO2 tension in the haemolymph and also O2 tension in the tracheal tubes.
 

33. Inspiration in cockroach is passive process and expiration is an active process. Justify?
A. Inspiration in the respiration of cockroach is a passive process, because it is performed by relaxation of muscles, and expiration is active process as it is performed by contraction of muscles.
 

34. The nitrogenous wastes in Periplaneta are removed from the body through alimentary canal. Why?
A. Excretion through alimentary canal in the cockroach is an adaptation for conservation of water, as it is survival technique to live as a terrestrial animal.
 

35. How does the cuticle of a cockroach help in excretion?
A. Some amounts of  nitrogenous wastes may be deposited under the cuticle, and it is removed during ecdysis.
 

36. How do fat bodies help in excretion?
A. The specialized cells, called urate cells of the fat bodies may absorb uric acid directly from the haemolymph, then store it during life time. This is a process of 'storage excretion'.
 

37. What is 'storage excretion'?
A. The urate cells of corpora adiposa absorb and store uric acid a during life time and this method is called storage excretion.
 

38. In which part of the alimentary canal of Periplaneta more water is  reabsorbed?
A. In the cockroach, more water is reabsorbed back into the blood in the ileum and rectum.
 

39. List out the organs associated with excretion in Periplaneta?
A. Excretion is performed by malpighian tubules, fat bodies, uricose glands, and cuticle in the cockroach.
 

40. Which part of malpighian tubules extract water, salts and nitrogenous wastes from the haemolymph?
A. The distal, secretary portion of each malpighian tubule extracts  nitrogenous wastes, excess water, salts, and CO2 from the haemolymph.
 

41. Which structure of cockroach acts as sensory and endocrine centre?
A. Brain or supra-oesophageal ganglion acts as sensory and endocrine center.
 

42. Distinguish between scolopidia and sensillae.
A. Scolopidia are subcuticular, receptor units, concerned with reception of movements and associated with chordotonal, subgenual, and tymponal organs located in pedicels and flagella of antennae, proximal parts of tibiae of legs and anal cerci respectively. Sensillae are sensory cuticular receptor units, concerned with reception of chemicals.
 

43. How is the ommatidium of cockroach different from that of a diurnal insect?
A. In diurnal insects, apposition image is formed by mosaic vision, in which the light rays enter through cornea converge on rhabdom, forming a part of object as a small image as light rays are prevented to enter adjacent ommatidia as pigment sheath prevents.
 

44. How many segmental ganglia are present on the ventral nerve cord of cockroach?
A. There are 9 segmental ganglia on ventral nerve cord of the cockroach. Three are present in thoracic region one in each thoracic segment, and six are present in abdominal region. First four abdominal ganglia are serially present in first four abdominal segments, fifth abdominal ganglion is present in 6th abdominal segment, and sixth abdominal ganglion is situated in seventh abdominal segment.
 

45. Which of the abdominal ganglia is the largest and why?
A. Sixth abdominal ganglion is the largest and is located in the seventh abdominal segment, and formed by fusion of 7th, 8th, 9th and 10th abdominal ganglia.
 

46. Name the structural and functional unit of compound eye of cockroach. How many such units are present in a single compound eye?
A. The structural and functional units of each compound eye are ommatidia, and each compound eye contains 2,000 ommatia.
 

47. Why is the brain called the principal sensory centre in cockroach?
A. The brain of cockroach is sensory centre, because it receives sensory impulses from antennae, labrum, and compound eyes, through antennal, labral, and optic nerves respectively.
 

48. Which parts of an ommatidium constitute dioptrical region?
A. The region of ommatidium containing cornea and crystalline cone constitutes dioptrical or focussing area.
 

49. Distinguish between apposition image and superposition image.
A. Apposition image is formed in diurnal insects by mosaic vision, in which juxtaposition of small parts of visual field are formed. Superposition image is formed in nocturnal insects in which the parts of visual field are overlapped one another, forming a blurred or superposition image.
 

50. List out the characters that help in understanding the difference between male and female cockroaches.
A. Male and female cockroaches exhibit sexual dimorphism both externally and internally. The size of abdomen in female cockroach is shorter and broader, with absense of anal styles and presence of brood pouch. In male abdomen is narrow and possess anal styles.
 

51. What is the function of mushroom gland in cockroach?
A. Mushroom gland in male reproductive system of the cockroach functions as an accessory reproductive gland, and forms the layers around spermatophores in the seminal vesicles and also nourish them.
 

52. Compare the utriculi majores and utriculi breviores of the mushroom gland functionally.
A. Utriculi majores and utriculi breviores of male cockroach function as formation of inner layer of the spermatophore and nourish the spermatozoa respectively.
 

53. How many ovarioles are present in a single ovary of Periplaneta and what are the two parts of single ovariole?
A. Each ovary of the cockroach consists of eight tubules, called ovarian tubules or ovarioles. Each ovariole consists of tapering anterior filament, called germarium and wider posterior, called vitellarium.
 

54. What are phallomeres?
A. In cockroach, the phallomeres are present around the male genital pore and are called gonapophyses, which assist the animal in copulation and be considered as external genitalia, made up of chitinous plates.
 

55. What are gonapophyses?
A. Gonapophyses are external genitalia of male and female cockroaches. In male, there are three gonapophyses that assist in copulation and three pairs in females that are ovipositors and copulatory organs.
 

56. How is colleterial gland helpful in reproduction of Periplaneta?
A. A pair of colleterial glands in female Periplaneta secretes a hard egg case (ootheca) around the eggs.
 

57. What is paurometabolous development?
A. Gradual development of nymphs by ecdysis into an adult in the life history of cockroach is called paurometabolic metamorphosis.
 

Short Answer Type Questions
1. Draw a neat labeled diagram of the mouth parts of cockroach?
A.

2. Describe the physiology of digestion in cockroach?
A. * Cockroach is an omnivorous insect.
* After swallowing the food, it reaches the crop through oesophagus and pharynx.
* Digestive juices mix with food in the crop, and food is partially digested in it.
* Partially digested food enters ventriculus after filtering in the gizzard by the bristles.

* Digested food is absorbed into the blood in the ventriculus (mesenteron)
* Undigested food moves through ileum, colon, and rectum, where excess water is reabsorbed by rectal papillae and finally is defaecated as dry pellets through the anus.
 

3. Draw a neat labeled diagram of the salivary apparatus of  cockroach?
A.

 

4. What is haemocoel? Describe it with reference to Periplaneta.
A. The body cavity of cockraoch is called haemocoel, as it is filled with haemolymph.
* Haemocoel is divided into 3 chambers or sinuses (pericardial, perivisceral, and perineural) by two muscular membranes, called dorsal diaphragm and ventral diaphragm.
* Pericardial sinus contains the heart, perineural sinus contains ventral nerve cord, and perivisceral sinus contains viscera, which is the largest.
* A series of paired muscles, called alary muscles is present on lateral sides of the body and attached to dorsal diaphragm on one side and terga on other side.
 

5. Describe the structure and function of the heart in Perplaneta?
A. * The heart of cockraoch is long, tubular, muscular, contractile, pumping organ, runs through mid-dorsal line of the body, beneath the terga of thorax and abdomen.
* Heart consists of 13 chambers. Each chamber opens into another chamber in front of it.
* Anterior end of the heart is open and forms dorsal aorta, which is only blood vessel present while posterior end is closed.
* Each chamber's posterior end, except 13th, opens into pericardial sinus through a pair of openings called ostia, which have valves that allow passage of blood from pericardial sinus into the heart.
 

6. Describe the process of blood circulation in Periplaneta.
A. * In cockroach, the blood flows forward in the heart as the result of contractions in the wall of heart.
* Finally, the blood enters the head sinus through dorsal aorta.
* From aorta, the blood flows into perivisceral sinus and perineural sinus.
* When alary muscles contract, pericardial membrane is pulled down as the volume of pericardial sinus increases, forcing the blood to enter into pericardial sinus through small apertures in the pericardial membrane from perivisceral and perineural sinuses.
* From pericardial sinus, the blood enters the heart through ostia.

 

7. How do contraction and relaxation of alary muscles help in circulation?
A. * In cockroach, when alary muscles contract the pericardial septum is pulled down resulting in increase the size of pericardial sinus.
* Then, the blood flows from perivisceral sinus into the pericardial sinus through small apertures in the pericardial septum.
* When alary muscles relax, the pericardial septum is brought upwards to its original position, resulting in forcing the blood to enter the heart chambers.
 

8. Describe the structure of trachea of cockroach.
A. In cockroach, the wall of trachea is made up of three layers, i.e. outer basement membrane, middle one cell thick epithelium, and inner cuticular layer, called intima, which produces spiral thickenings along the length of the trachea, called taenidia, which prevent collapsing of trachea when air is absent.
9. Explain the structure of malpighian tubules?
A. * In cockroach, the malpighian tubules are excretory organs.
* Each malpighian tubule is long, unbranched tubule attached at the extreme anterior end of the hindgut, opening into lumen of ileum.
* Each tubule is blind at distal end and open into lumen of hindgut.
* There are 100-150 malpighian tubules arranged in 6-8 bundles, each bundle contains 15-25 tubules.
* The lumen of each tubule is lined by single layer of glandular epithelium with brush border.
* The distal portion of the tubule is secretory and the proximal portion is absorptive in function.
 

10. What are different excretory organs in Periplaneta? Describe the process of excretion in detail?
A. Different excretory organs of Periplaneta include
1. Malpighian tubules
2. Fat bodies
3. Uricose glands
4. Nephrocytes
5. Cuticle
* Glandular cells of the malpighian tubules absorb and secrete excess water, salts, nitrogenous wastes, CO2 from the haemolymph into the lumen.
* The cells of the proximal part of malpighian tubules reabsorb water and some important inorganic salts back into the haemolymph. This action produces highly concentrated urine, which is pushed into the hindgut by regular contraction of tubules.
* More water is reabsorbed from the urine by rectal papilla, producing solid uric acid excretory product, which may be discharged along with faecal matter through anus.
* Urate cells of fat bodies absorb and store uric acid throughout life. It is called storage excretion.
* Some amount of uric acid may be stored into the mushroom gland in the males and discharged during copulation.
* Some amount of uric acid may be deposited on the cuticle and removed during ecdysis along with cuticle.
 

11. How does Periplaneta conserve water? Explain it with the help of excretion in it.
A. * The cells of proximal part of malpighian tubules reabsorb excess water from excretory product to synthesize concentrated urine.
* Nitrogenous is removed through alimentary canal rather than separate urinary system is an adaptation to conserve water in terrestrial insects, and also helps to form dry uric acid excretory material.
 

12. Describe the structure of an ommtidium and label its parts.
A. * Structural and functional units of a compound eye are ommatidia, and each compound eye has 2,000 ommatidia.
* Each ommatidium has a cornea, which is biconvex, transparent part of the cuticle, representing a facet of an eye.
* Just below the cornea, a pair of corneagen, or lenticular cells is present and secretes the cornea during moulting. These cells also form primary pigment sheath or iris pigment sheath.
* Vitrellae or cone cells are four in number, surrounding crystalline cone and secrete it, as they lie below corneagen cells.
* Crystalline cone is triangular, elongated, transparent structure, surrounded by vitrillae.
Primary pigment cells surround the vitrillae. Cornea and crystalline cone together form dioptrical or focussing region of an ommatidium.
* Retinulae are 7 retinular cells that surround the rhabdome and form it. Microvilli of each retinular cell form rhabdomere and all the rhabdomeres together form rhabdome in the centre. Retinulae are photoreceptor nerve cells that lie on basement membrane and leave the ommatidium as optic sensory nerve fibers to the brain.
* Rhabdome and retinulae together form retinular or receptor region of the ommatidium.
 

13. Draw a neat and labeled diagram of ommatidium.
A: 

 

14. How can you identify the male and female cockroaches? Explain it describing the cheif features of the external and internal genetalia.
A. *  Cockroach is unisexual animal.
* Male and female cockroaches exhibit sexual dimorphism both externally and internally.
* The abdomen of female is short and broad with respect to that of male animal.
* Female cockroach has brood pouch on ventral surface of the abdomen and it is absent in males.
* Male cockroach has a pair of anal styles at the posterior end of the abdomen and it is absent in females.
* Male and female reproductive organs are well developed in these animals.
* Male external genitalia or phallomeres are three in number, while female external genitalia are three pairs in number and their structure are different from each other.
 

15. Describe the male reproductive system of cockroach.
A. * Male reproductive system of the cockroach includes one pair of testes, one pair of Vasa deferentia, an ejaculatory duct, a mushroom gland, seminal vesicles, a phallic gland, a genital pouch and three phallomeres.
* One pair of testes lies one on either dorso - lateral side of 4th to 6th abdominal segments. They produce spermatozoa.
* A pair of vasa deferentia one from each testes arises, and run posteriorly downwards to open the ejaculatory duct. They transport spermatazoa.
* Ejaculatory duct is single, median, and muscular duct that opens into genital pouch through male genital pore.
* The junction of two vasa deferentia and ejaculatory duct, is surrounded by an elaborate mushroom gland consisting of numerous, compact, finger-like blind tubules (large, peripheral tubules are called utriculi majores and short, central tubules are called utriculi breviores.)
* Present on the ventral surface of anterior part of ejaculatory duct are two groups of white sacs constituting seminal vesicles meant for storage of sperms.
* A club-shaped gland, called phallic or conglobate gland is present below the ejaculatory duct in the 5th abdominal segment. Its duct also opens into the genital pouch by the side of male genital pore. This gland secretes the outer layer or spermatophore.
* Male genital pouch lies at the end of abdomen, into which male genital pore, duct of phallic gland, and anus open.
 

16. Describe the female reproductive system of cockroach.
A. *  Female reproductive system of the cockroach consists of
1. a pair of ovaries
2. a pair of oviducts
3. a common oviduct (vagina)
4. female genital pore
5. a pair of spermathecae
6. spermathecal papilla
7. a pair of colleterial glands
8. three pairs of gonapophyses
* There are a pair of ovaries, lying between 2nd and 6th abdominal segments. Each ovary is made up of 8 ovarian tubules or ovarioles. Each ovariole is tapering at anterior end (germarium) and under at posterior end (vitellarium). All eight ovarioles at the posterior end unite with one another to form an oviduct.
* Both the oviducts unite and constitute a common oviduct or vagina, which opens into genital chamber by female genital aperture, on 8th sternum.
* A pair of spermathecae of unequal size unite to form a short common duct, which opens into genital chamber near female genital aperture on a small spermathecal papilla.
* A pair of highly branched collaterial glands, lies behind and above the ovaries. These open into genital chamber separately.
* Genital pouch is formed by 7th, 8th and 9th sterna and contains female genital aperture, spermathecal opening, and openings of colleterial glands.
* Female gonopore is surrounded by three symmetrically arranged, plate-like, chitinous processes, which are called gonopophyses or female external genitalia, which are ovipositor organs.