Phylum — Arthropoda
Class — Insecta
Order — Dictyoptera
Genus — Periplaneta
Species — americana
Cockroach is a nocturnal and an omnivorous insect, found all over the world.
There are 3 species namely: Periplaneta americana, Blatta orientalis and Blatta germanica
MORPHOLOGY
$\displaystyle \small \bullet$ Cockroach has an elongated, bilaterally symmetrical and dorsoventrally flattened body.
$\displaystyle \small \bullet$ Body can be divisible into head, thorax and abdomen.
$\displaystyle \small \bullet$ Entire body is covered by a tough exoskeleton of chitin. The wax layer on the top of exoskeleton makes the body smooth, water-proof and prevent evaporation of water.
$\displaystyle \small \bullet$ The exoskeleton is in the form of hardened plates called sclerietes. The dorsal plate is called tergum and the ventral sternum. They are joined to each other by a thin and flexible articular membrane (arthrodial membrane).
$\displaystyle \small \bullet$ Head is triangular in shape and is formed by the fusion of six segments and shows great mobility in all directions due to flexible neck.
$\displaystyle \small \bullet$ The head bears a pair of compound eyes, a pair antennae, they have sensory receptors that help in monitoring the environment.
$\displaystyle \small \bullet$ Anterior end of the head bears appendages forming biting and chewing type of mouth parts.
$\displaystyle \small \bullet$ The mouth parts consists of a labrum (upper lip), a pair of mandibles, a pair of maxillae and a labium (lower lip). A median flexible lobe, acting as tongue (hypopharynx), lies within the cavity enclosed by the mouthparts.
$\displaystyle \small \bullet$ Thorax consists of three parts – prothorax,mesothorax and metathorax.
$\displaystyle \small \bullet$ The head is connected with thorax by a short extension of the prothorax known as the neck.
$\displaystyle \small \bullet$ Each thoracic segment bears a pair of walking legs. They have three pairs of legs.
$\displaystyle \small \bullet$ The first pair of wings arises from mesothorax and the second pair from metathorax.
$\displaystyle \small \bullet$ Forewings (mesothoracic) called tegmina are opaque, dark and leathery and cover the hind wings.
$\displaystyle \small \bullet$ The hind wings are transparent, membranous and are used in flight.
$\displaystyle \small \bullet$ The abdomen in both males and females consists of 10 segments.
$\displaystyle \small \bullet$ In females, the $\displaystyle \small 7^{th}$ sternum is boat shaped and together with the $\displaystyle \small 18^{th}$ and $\displaystyle \small 9^{th}$ sterna forms a brood or genital pouch whose anterior part contains female gonopore, spermathecal pores and collateral glands.
$\displaystyle \small \bullet$ In males, genital pouch or chamber lies at the hind end of abdomen bounded dorsally by $\displaystyle \small 9^{th}$ and $\displaystyle \small 10^{th}$ terga and ventrally by the $\displaystyle \small 9^{th}$ sternum. It contains dorsal anus, ventral male genital pore and gonapophysis.
$\displaystyle \small \bullet$ Males bear a pair of short, thread like anal styles which are absent in females.
$\displaystyle \small \bullet$ In both sexes, the $\displaystyle \small 10^{th}$ segment bears a pair of jointed filamentous structures called anal cerci.
$\displaystyle \small \bullet$ The slit openings on either side of body are called spiracles. The spiracles let air into trachea.
$\displaystyle \small \bullet$ Stink glands are present in the $\displaystyle \small 5^{th}$ and $\displaystyle \small 6^{th}$ terga of abdomen.
ANATOMY
Digestive System
$\displaystyle \small \bullet$ The alimentary canal of cockroach is divided into three regions: foregut, midgut and hindgut.
$\displaystyle \small \bullet$ The mouth has cutting and biting type of mouth parts which opens into a short tubular pharynx, leading to a narrow tubular passage called oesophagus.
$\displaystyle \small \bullet$ This in turn opens into a sac like structure called crop, used for storing of food. The crop is followed by gizzard.
$\displaystyle \small \bullet$ Gizzard has an outer layer of thick circular muscles and thick inner cuticle, forming six highly chitinous plate called teeth which helps in grinding the food particles.
$\displaystyle \small \bullet$ The entire foregut is lined by cuticle.
$\displaystyle \small \bullet$ A ring of 6-8 blind tubules called hepatic or gastric caecae is present at the junction of foregut and midgut, which secrete digestive juice.
$\displaystyle \small \bullet$ At the junction of midgut and hindgut is present another ring of 100-150 yellow coloured thin filamentous Malphigian tubules. They help in removal of excretory products from haemolymph.
$\displaystyle \small \bullet$ The hindgut is broader than midgut and is differentiated into ileum, colon and rectum. The rectum opens out through anus.
Circulatory System
$\displaystyle \small \bullet$ Cockroach has an open type blood vascular system.
$\displaystyle \small \bullet$ Blood vessels are poorly developed and open into space (haemocoel).
$\displaystyle \small \bullet$ Visceral organs located in the haemocoel are bathed in blood (haemolymph).
$\displaystyle \small \bullet$ The haemolymph is composed of colourless plasma and haemocytes.
$\displaystyle \small \bullet$ Heart of cockroach consists of elongated muscular tube lying in mid dorsal line of thorax and abdomen. Heart consists 13 chambers of which 3 in thoracic and 10 in abdomen.
$\displaystyle \small \bullet$ It is differentiated into funnel shaped chambers with ostia on either side.
$\displaystyle \small \bullet$ Blood from sinuses enter heart through ostia and is pumped anteriorly to sinuses again.
$\displaystyle \small \bullet$ Blood is colourless due to absence of pigments.
Respiratory System
$\displaystyle \small \bullet$ The respiratory system consists of a network of trachea that open through 10 pairs of small holes called spiracles present on the lateral side of the body.
$\displaystyle \small \bullet$ Thin branching tubes carry oxygen from the air to all the parts.
$\displaystyle \small \bullet$ The opening of the spiracles is regulated by the sphincters.
$\displaystyle \small \bullet$ Exchange of gases take place at the tracheoles by diffusion.
$\displaystyle \small \bullet$ The passage of air is: spiracles--->trachea-->tracheoles--->tissues.
Excretory System
$\displaystyle \small \bullet$ Excretion is performed by Malphigian tubules.
$\displaystyle \small \bullet$ They absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut. Therefore, this insect is called uricotelic.
$\displaystyle \small \bullet$ In addition to the fat body, nephrocytes and urecose glands also help in excretion.
Nervous System
$\displaystyle \small \bullet$ The nervous system of cockroach consists of a series of fused, segmentally arranged ganglia, joined by paired longitudinal connectives on the ventral side.
$\displaystyle \small \bullet$ Three ganglia lie in the thorax, and six in the abdomen.
$\displaystyle \small \bullet$ The nervous system of cockroach is spread throughout the body.
$\displaystyle \small \bullet$ The head holds a bit of a nervous system while the rest is situated along the ventral part of its body.
$\displaystyle \small \bullet$ If the head of a cockroach is cut off, it will still live for as long as one week.
$\displaystyle \small \bullet$ In the head region, the brain is represented by supra-oesophageal ganglion which supplies nerves to antennae and compound eyes.
$\displaystyle \small \bullet$ In cockroach, the sense organs are antennae, eyes, maxillary palps, labial palps, anal cerci, etc.
$\displaystyle \small \bullet$ The compound eyes are situated at the dorsal surface of the head. Each eye consists of about 2000 hexagonal smaller eye called ommatidia. With the help of several ommatidia, it receives 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).
Reproductive System
$\displaystyle \small \bullet$ Sexes are separate hence they are called as dioecious.
Male reproductive system consists of a pair of testis on each side, spreading from $\displaystyle \small 4^{th}$ to $\displaystyle \small 6^{th}$ abdominal segments.
$\displaystyle \small \bullet$ Vas deferens is a tube, arises from each testis, which opens into ejaculatory duct through seminal vesicle.
$\displaystyle \small \bullet$ Ejaculatory duct opens into male gonopore present ventral to anus.
$\displaystyle \small \bullet$ Accessory reproductive gland is a mushroom shaped gland present in the $\displaystyle \small 6^{th}$–$\displaystyle \small 7^{th}$ abdominal segments which pours its secretion in the ejaculatory duct.
$\displaystyle \small \bullet$ External genitilia are represented by male gonapophysis or phallomere.
$\displaystyle \small \bullet$ The sperms are produced by testes and stored in the seminal vescicle. They are attached to forms bundles called spermatophores. The spermatophores are discharged during mating.
Female reproductive system consists of two large ovaries, lying in $\displaystyle \small 2^{nd}$–$\displaystyle \small 6^{th}$ abdominal segments.
$\displaystyle \small \bullet$ Each ovary is formed of a group of 8 ovarian tubules or ovarioles, containing a chain of developing ova.
$\displaystyle \small \bullet$ Oviducts of each ovary unite into a single median oviduct (also called vagina).
$\displaystyle \small \bullet$ Common oviduct opens into the genital chamber. The genital chamber and vestibulum together forms genital pouch. It opens outside by genital pore.
$\displaystyle \small \bullet$ Six chitinous plates surrounding the genital pore are called gonapophysis.
$\displaystyle \small \bullet$ A pair of spermathecae are present in the $\displaystyle \small 6^{th}$ segment that open into the genital chamber.
Fertilization
$\displaystyle \small \bullet$ The male and female cockroaches come together by their posterior ends, with the help of male phallomeres.
$\displaystyle \small \bullet$ The sperms are transferred through spermatophores to the genital chamber of female cockroach.
$\displaystyle \small \bullet$ The sperms are deposited in the spermatheca of female reproductive system.
$\displaystyle \small \bullet$ The eggs are discharged from both the ovaries and pass into the genital chamber.
$\displaystyle \small \bullet$ In the genital chamber eggs are fertilised by the sperms coming from spermatheca.
$\displaystyle \small \bullet$ The secretion of collaterial glands forms a capsulse around fertilized eggs, it is called eggcase or Ootheca.
$\displaystyle \small \bullet$ They are dark reddish containing 14—16 fertilised eggs in two rows. They are dropped or glued in dark places.
$\displaystyle \small \bullet$ The development of P. Americana is parometabolous, meaning there is development through nymphal stage (larva without wings).
$\displaystyle \small \bullet$ The nymphs look very much like adults. The nymph grows by moulting about 13 times to reach the adult form. The next to last nymphal stage has wing pads but only adult cockroaches have wings.
Class — Insecta
Order — Dictyoptera
Genus — Periplaneta
Species — americana
Cockroach is a nocturnal and an omnivorous insect, found all over the world.
There are 3 species namely: Periplaneta americana, Blatta orientalis and Blatta germanica
MORPHOLOGY
$\displaystyle \small \bullet$ Cockroach has an elongated, bilaterally symmetrical and dorsoventrally flattened body.
$\displaystyle \small \bullet$ Body can be divisible into head, thorax and abdomen.
$\displaystyle \small \bullet$ Entire body is covered by a tough exoskeleton of chitin. The wax layer on the top of exoskeleton makes the body smooth, water-proof and prevent evaporation of water.
$\displaystyle \small \bullet$ The exoskeleton is in the form of hardened plates called sclerietes. The dorsal plate is called tergum and the ventral sternum. They are joined to each other by a thin and flexible articular membrane (arthrodial membrane).
$\displaystyle \small \bullet$ Head is triangular in shape and is formed by the fusion of six segments and shows great mobility in all directions due to flexible neck.
$\displaystyle \small \bullet$ The head bears a pair of compound eyes, a pair antennae, they have sensory receptors that help in monitoring the environment.
$\displaystyle \small \bullet$ Anterior end of the head bears appendages forming biting and chewing type of mouth parts.
$\displaystyle \small \bullet$ The mouth parts consists of a labrum (upper lip), a pair of mandibles, a pair of maxillae and a labium (lower lip). A median flexible lobe, acting as tongue (hypopharynx), lies within the cavity enclosed by the mouthparts.
$\displaystyle \small \bullet$ Thorax consists of three parts – prothorax,mesothorax and metathorax.
$\displaystyle \small \bullet$ The head is connected with thorax by a short extension of the prothorax known as the neck.
$\displaystyle \small \bullet$ Each thoracic segment bears a pair of walking legs. They have three pairs of legs.
$\displaystyle \small \bullet$ The first pair of wings arises from mesothorax and the second pair from metathorax.
$\displaystyle \small \bullet$ Forewings (mesothoracic) called tegmina are opaque, dark and leathery and cover the hind wings.
$\displaystyle \small \bullet$ The hind wings are transparent, membranous and are used in flight.
$\displaystyle \small \bullet$ The abdomen in both males and females consists of 10 segments.
$\displaystyle \small \bullet$ In females, the $\displaystyle \small 7^{th}$ sternum is boat shaped and together with the $\displaystyle \small 18^{th}$ and $\displaystyle \small 9^{th}$ sterna forms a brood or genital pouch whose anterior part contains female gonopore, spermathecal pores and collateral glands.
$\displaystyle \small \bullet$ In males, genital pouch or chamber lies at the hind end of abdomen bounded dorsally by $\displaystyle \small 9^{th}$ and $\displaystyle \small 10^{th}$ terga and ventrally by the $\displaystyle \small 9^{th}$ sternum. It contains dorsal anus, ventral male genital pore and gonapophysis.
$\displaystyle \small \bullet$ Males bear a pair of short, thread like anal styles which are absent in females.
$\displaystyle \small \bullet$ In both sexes, the $\displaystyle \small 10^{th}$ segment bears a pair of jointed filamentous structures called anal cerci.
$\displaystyle \small \bullet$ The slit openings on either side of body are called spiracles. The spiracles let air into trachea.
$\displaystyle \small \bullet$ Stink glands are present in the $\displaystyle \small 5^{th}$ and $\displaystyle \small 6^{th}$ terga of abdomen.
ANATOMY
Digestive System
$\displaystyle \small \bullet$ The alimentary canal of cockroach is divided into three regions: foregut, midgut and hindgut.
$\displaystyle \small \bullet$ The mouth has cutting and biting type of mouth parts which opens into a short tubular pharynx, leading to a narrow tubular passage called oesophagus.
$\displaystyle \small \bullet$ This in turn opens into a sac like structure called crop, used for storing of food. The crop is followed by gizzard.
$\displaystyle \small \bullet$ Gizzard has an outer layer of thick circular muscles and thick inner cuticle, forming six highly chitinous plate called teeth which helps in grinding the food particles.
$\displaystyle \small \bullet$ The entire foregut is lined by cuticle.
$\displaystyle \small \bullet$ A ring of 6-8 blind tubules called hepatic or gastric caecae is present at the junction of foregut and midgut, which secrete digestive juice.
$\displaystyle \small \bullet$ At the junction of midgut and hindgut is present another ring of 100-150 yellow coloured thin filamentous Malphigian tubules. They help in removal of excretory products from haemolymph.
$\displaystyle \small \bullet$ The hindgut is broader than midgut and is differentiated into ileum, colon and rectum. The rectum opens out through anus.
Circulatory System
$\displaystyle \small \bullet$ Cockroach has an open type blood vascular system.
$\displaystyle \small \bullet$ Blood vessels are poorly developed and open into space (haemocoel).
$\displaystyle \small \bullet$ Visceral organs located in the haemocoel are bathed in blood (haemolymph).
$\displaystyle \small \bullet$ The haemolymph is composed of colourless plasma and haemocytes.
$\displaystyle \small \bullet$ Heart of cockroach consists of elongated muscular tube lying in mid dorsal line of thorax and abdomen. Heart consists 13 chambers of which 3 in thoracic and 10 in abdomen.
$\displaystyle \small \bullet$ It is differentiated into funnel shaped chambers with ostia on either side.
$\displaystyle \small \bullet$ Blood from sinuses enter heart through ostia and is pumped anteriorly to sinuses again.
$\displaystyle \small \bullet$ Blood is colourless due to absence of pigments.
Respiratory System
$\displaystyle \small \bullet$ The respiratory system consists of a network of trachea that open through 10 pairs of small holes called spiracles present on the lateral side of the body.
$\displaystyle \small \bullet$ Thin branching tubes carry oxygen from the air to all the parts.
$\displaystyle \small \bullet$ The opening of the spiracles is regulated by the sphincters.
$\displaystyle \small \bullet$ Exchange of gases take place at the tracheoles by diffusion.
$\displaystyle \small \bullet$ The passage of air is: spiracles--->trachea-->tracheoles--->tissues.
Excretory System
$\displaystyle \small \bullet$ Excretion is performed by Malphigian tubules.
$\displaystyle \small \bullet$ They absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut. Therefore, this insect is called uricotelic.
$\displaystyle \small \bullet$ In addition to the fat body, nephrocytes and urecose glands also help in excretion.
Nervous System
$\displaystyle \small \bullet$ The nervous system of cockroach consists of a series of fused, segmentally arranged ganglia, joined by paired longitudinal connectives on the ventral side.
$\displaystyle \small \bullet$ Three ganglia lie in the thorax, and six in the abdomen.
$\displaystyle \small \bullet$ The nervous system of cockroach is spread throughout the body.
$\displaystyle \small \bullet$ The head holds a bit of a nervous system while the rest is situated along the ventral part of its body.
$\displaystyle \small \bullet$ If the head of a cockroach is cut off, it will still live for as long as one week.
$\displaystyle \small \bullet$ In the head region, the brain is represented by supra-oesophageal ganglion which supplies nerves to antennae and compound eyes.
$\displaystyle \small \bullet$ In cockroach, the sense organs are antennae, eyes, maxillary palps, labial palps, anal cerci, etc.
$\displaystyle \small \bullet$ The compound eyes are situated at the dorsal surface of the head. Each eye consists of about 2000 hexagonal smaller eye called ommatidia. With the help of several ommatidia, it receives 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).
Reproductive System
$\displaystyle \small \bullet$ Sexes are separate hence they are called as dioecious.
Male reproductive system consists of a pair of testis on each side, spreading from $\displaystyle \small 4^{th}$ to $\displaystyle \small 6^{th}$ abdominal segments.
$\displaystyle \small \bullet$ Vas deferens is a tube, arises from each testis, which opens into ejaculatory duct through seminal vesicle.
$\displaystyle \small \bullet$ Ejaculatory duct opens into male gonopore present ventral to anus.
$\displaystyle \small \bullet$ Accessory reproductive gland is a mushroom shaped gland present in the $\displaystyle \small 6^{th}$–$\displaystyle \small 7^{th}$ abdominal segments which pours its secretion in the ejaculatory duct.
$\displaystyle \small \bullet$ External genitilia are represented by male gonapophysis or phallomere.
$\displaystyle \small \bullet$ The sperms are produced by testes and stored in the seminal vescicle. They are attached to forms bundles called spermatophores. The spermatophores are discharged during mating.
Female reproductive system consists of two large ovaries, lying in $\displaystyle \small 2^{nd}$–$\displaystyle \small 6^{th}$ abdominal segments.
$\displaystyle \small \bullet$ Each ovary is formed of a group of 8 ovarian tubules or ovarioles, containing a chain of developing ova.
$\displaystyle \small \bullet$ Oviducts of each ovary unite into a single median oviduct (also called vagina).
$\displaystyle \small \bullet$ Common oviduct opens into the genital chamber. The genital chamber and vestibulum together forms genital pouch. It opens outside by genital pore.
$\displaystyle \small \bullet$ Six chitinous plates surrounding the genital pore are called gonapophysis.
$\displaystyle \small \bullet$ A pair of spermathecae are present in the $\displaystyle \small 6^{th}$ segment that open into the genital chamber.
Fertilization
$\displaystyle \small \bullet$ The male and female cockroaches come together by their posterior ends, with the help of male phallomeres.
$\displaystyle \small \bullet$ The sperms are transferred through spermatophores to the genital chamber of female cockroach.
$\displaystyle \small \bullet$ The sperms are deposited in the spermatheca of female reproductive system.
$\displaystyle \small \bullet$ The eggs are discharged from both the ovaries and pass into the genital chamber.
$\displaystyle \small \bullet$ In the genital chamber eggs are fertilised by the sperms coming from spermatheca.
$\displaystyle \small \bullet$ The secretion of collaterial glands forms a capsulse around fertilized eggs, it is called eggcase or Ootheca.
$\displaystyle \small \bullet$ They are dark reddish containing 14—16 fertilised eggs in two rows. They are dropped or glued in dark places.
$\displaystyle \small \bullet$ The development of P. Americana is parometabolous, meaning there is development through nymphal stage (larva without wings).
$\displaystyle \small \bullet$ The nymphs look very much like adults. The nymph grows by moulting about 13 times to reach the adult form. The next to last nymphal stage has wing pads but only adult cockroaches have wings.
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