The Cockroach
Periplaneta americana
Class 11 · Structural Organisation in Animals — a complete, exam-first note. Every NCERT fact, explained in simple language, with high-yield flags, mnemonics and NEET-style PYQ practice.
Identity, habit & habitat
A cockroach is a brown-to-black insect that has quietly perfected the art of survival — so well that a famous (NCERT-backed) fact is that it can survive about a week even after its head is cut off.
Cockroaches belong to Class Insecta of Phylum Arthropoda. They are nocturnal omnivores living in damp places worldwide, and have become common house residents — which makes them serious pests and vectors of several diseases. Size ranges from about ¼ inch to 3 inches (0.6–7.6 cm). The common species studied for NEET is Periplaneta americana, with adults about 34–53 mm long; in males the wings extend beyond the tip of the abdomen.
- Common name
- American cockroach
- Scientific name
- Periplaneta americana
- Phylum
- Arthropoda
- Class
- Insecta
- Body symmetry
- Bilateral, triploblastic, segmented, coelomate
- Excretion
- Uricotelic (excretes uric acid)
Why this chapter is a guaranteed scorer
Cockroach sits inside Unit V – Structural Organisation in Plants and Animals, which carries roughly 5% weightage in NEET. Cockroach alone reliably delivers 1–2 questions per paper. The best part: questions are almost entirely direct recall of fixed anatomical facts — no reasoning traps, definite answers. Two or three focused sessions = full marks here, year after year.
| Year | Qs from cockroach | Sub-topic tested |
|---|---|---|
| 2024 | 1 | Nervous system — nerve ring & ganglia |
| 2023 | 2 | Malpighian tubules, reproductive system |
| 2022 | 1 | Digestive system — hepatic caeca |
| 2021 | 2 | Sense organs, reproductive structures |
| 2020 | 1 | External morphology — tagmata, segments |
| 2019 | 2 | Nervous system, Malpighian tubules |
| 2018 | 1 | Digestive system, gizzard function |
| 2017 | 2 | Reproductive system, oothecae |
| 2016 | 1 | Circulatory system — open type |
| 2015 | 2 | Morphology, fat body function |
External morphology
The body is segmented and divided into three distinct regions (tagmata): head, thorax and abdomen. The entire body is covered by a hard, brown chitinous exoskeleton. In each segment the exoskeleton forms hardened plates called sclerites — tergites on the dorsal (back) side and sternites on the ventral (belly) side — joined by a thin, flexible arthrodial (articular) membrane.
① Head
The head is triangular, lies at right angles to the body axis, and is formed by the fusion of 6 segments. Thanks to a flexible neck, it can move in all directions. It carries:
- A pair of compound eyes.
- A pair of thread-like antennae (sensory — monitor the environment) arising from sockets in front of the eyes.
- Biting & chewing mouthparts: labrum (upper lip), a pair of mandibles, a pair of maxillae, a labium (lower lip), and a tongue-like median lobe, the hypopharynx.
② Thorax
Made of three parts — prothorax, mesothorax, metathorax. Each thoracic segment bears one pair of walking legs (so 3 pairs total). Two pairs of wings are present:
- Forewings (tegmina) — arise from the mesothorax; opaque, dark, leathery; cover the hind wings at rest.
- Hind wings — arise from the metathorax; transparent, membranous; used in flight.
③ Abdomen
The abdomen has 10 segments in both sexes. This region is the easiest place to tell males and females apart — a classic NEET point:
| Feature | Male ♂ | Female ♀ |
|---|---|---|
| Anal styles | Present (a pair, thread-like) | Absent |
| Anal cerci (10th segment) | Present | Present (in both sexes) |
| Genital pouch | At hind end (9th–10th terga, 9th sternum) | Brood/genital pouch from 7th, 8th, 9th sterna |
| Wings | Extend beyond abdomen tip | Shorter |
Digestive system
The alimentary canal lies in the body cavity and is divided into three regions: foregut, midgut and hindgut. Trace the food's journey:
Mouth → Pharynx → Oesophagus → Crop → Gizzard (proventriculus) → Hepatic caeca → Midgut (mesenteron) → Ileum → Colon → Rectum → Anus.
- Crop — a sac-like structure for storing food.
- Gizzard / proventriculus — has thick circular muscles and a thick inner cuticle forming 6 highly chitinous "teeth" that grind food. The entire foregut is lined by cuticle.
- Hepatic (gastric) caeca — a ring of 6–8 blind tubules at the junction of foregut and midgut; they secrete digestive juice.
- Salivary glands — a pair, present near the crop, with salivary reservoirs.
Circulatory system
The cockroach has an open circulatory system — blood is not confined to vessels. Vessels are poorly developed and open into large spaces collectively called the haemocoel, where the organs are simply bathed in blood.
- The blood is called haemolymph = colourless plasma + haemocytes. It has no respiratory pigment (so it does not carry oxygen — the tracheal system does that job).
- The heart is an elongated muscular tube along the mid-dorsal line of thorax and abdomen, differentiated into 13 funnel-shaped chambers with paired ostia on either side.
- Blood from the sinuses enters the heart through the ostia and is pumped anteriorly (forward) back to the sinuses.
Respiratory system
Respiration is by a network of air tubes called tracheae, which open to the outside through 10 pairs of small holes called spiracles on the lateral sides of the body. The tracheae branch into finer tracheoles that carry oxygen directly to every tissue.
- Spiracle openings are regulated by sphincters.
- Gas exchange happens at the tracheoles by simple diffusion.
Excretory system
Excretion is performed mainly by Malpighian tubules — the most tested structure in the whole chapter.
| Feature | Detail |
|---|---|
| Number | 100–150, thin, yellow, filamentous |
| Position | At the junction of midgut & hindgut (mesenteron–ileum) |
| Lining | Glandular + ciliated cells |
| Function | Absorb nitrogenous waste from haemolymph → convert to uric acid → excreted via hindgut |
Because the final waste is uric acid, the cockroach is uricotelic. Additional excretory help comes from the fat body, nephrocytes and urecose (uricose) glands.
Nervous system & sense organs
The nervous system is a chain of fused, segmentally arranged ganglia joined by paired longitudinal connectives, running along the ventral (belly) side — this is why a cockroach survives even after losing its head: most of its nervous system is in the body, not the head.
- Ganglia: 3 in the thorax + 6 in the abdomen.
- The "brain" is the supra-oesophageal ganglion (above the oesophagus); it supplies nerves to antennae and compound eyes.
- The sub-oesophageal ganglion lies below the oesophagus; the two are linked by circum-oesophageal connectives forming a nerve ring around the oesophagus.
Sense organs & vision
Sense organs include antennae, eyes, maxillary palps, labial palps and anal cerci. The compound eyes sit on the dorsal head surface. Each eye has about 2000 hexagonal ommatidia. Many ommatidia together give many small images of one object — this is mosaic vision: more sensitivity but less resolution, ideal for the cockroach's nocturnal (night) life.
Reproductive system
Cockroaches are dioecious (sexes separate) with internal fertilisation.
Male ♂
- A pair of testes — one on each side, in the 4th–6th abdominal segments.
- Each testis → vas deferens → seminal vesicle → ejaculatory duct → male gonopore (ventral to anus).
- Mushroom-shaped gland in the 6th–7th segments = accessory reproductive gland.
- External genitalia = gonapophyses / phallomeres (chitinous, asymmetrical).
- Sperms are glued into bundles called spermatophores, discharged during copulation.
Female ♀
- A pair of ovaries in the 2nd–6th abdominal segments.
- Each ovary = group of 8 ovarian tubules (ovarioles) with chains of developing ova.
- Oviducts unite into a single median oviduct (vagina) opening into the genital chamber.
- A pair of spermatheca in the 6th segment (stores sperm).
- Colleterial glands secrete the protective egg case, the ootheca.
Ootheca
Fertilised eggs are encased in a dark reddish-to-blackish-brown capsule called an ootheca, about 8 mm (3/8") long. On average a female produces 9–10 oothecae, each containing 14–16 eggs. Oothecae are dropped/glued in cracks of high humidity near food.
Development
Development of P. americana is paurometabolous — i.e., development through a nymphal stage, with incomplete metamorphosis. The nymphs look very much like the adults. A nymph grows by moulting about 13 times to reach the adult form. The next-to-last nymphal stage has wing pads, but only adults have full wings.
The one-page fact sheet
This is the table to revise 3 times before NEET. If you can reproduce it from memory, the cockroach questions are yours.
| System / Topic | Key structure | Number / Position / Function |
|---|---|---|
| Morphology | Body regions | Head + Thorax + Abdomen; abdomen = 10 segments |
| Morphology | Legs / Wings | 3 pairs legs; tegmina (meso-), hind wings (meta-) |
| Digestive | Gizzard teeth | 6 chitinous teeth; grinds food |
| Digestive | Hepatic caeca | 6–8; foregut–midgut junction; secrete enzymes |
| Circulatory | Heart | 13 chambers; open type; ostia; haemolymph colourless |
| Respiratory | Spiracles | 10 pairs; tracheae → tracheoles; diffusion |
| Excretory | Malpighian tubules | 100–150; midgut–hindgut junction; uric acid → uricotelic |
| Nervous | Ganglia | Brain = supra-oesophageal; 3 thoracic + 6 abdominal |
| Senses | Compound eye | ~2000 ommatidia; mosaic (nocturnal) vision |
| Repro (♂) | Testes / Mushroom gland | Testes 4–6th seg; mushroom gland 6–7th seg |
| Repro (♀) | Ovaries / Ootheca | Ovaries 2–6th seg; ootheca = 14–16 eggs; 9–10 produced |
| Development | Type | Paurometabolous; ~13 moults; wings only in adult |
Most-repeated topics (2015–2024)
Ranked by how often each appeared across the last 10 NEET papers (analysis source: eSaral):
| Rank | Topic | Appeared in |
|---|---|---|
| 1 | Malpighian tubules — position, number, uricotelic | 8 / 10 yrs |
| 2 | Nervous system — supra-oesophageal ganglion, nerve ring, ventral nerve cord | 7 / 10 |
| 3 | Compound eyes & mosaic vision | 6 / 10 |
| 4 | Ootheca — structure, egg number, colleterial gland | 6 / 10 |
| 5 | Hepatic caeca — position & function | 5 / 10 |
| 6 | Body tagmata & segment count | 5 / 10 |
| 7 | Open circulatory system — 13-chambered heart, ostia | 4 / 10 |
| 8 | Fat body — excretion + storage | 4 / 10 |
| 9 | Mushroom gland — male accessory gland | 3 / 10 |
| 10 | Tracheal system — 10 pairs of spiracles | 3 / 10 |
Mnemonics & memory tricks
Mouth · Pharynx · Esophagus · Crop · Gizzard · Hepatic caeca · Midgut · Ileum · Colon · Rectum · Anus.
NEET PYQ-pattern MCQs
Tap any question to reveal the answer & explanation. Questions marked NEET favourite test facts that have repeatedly appeared in NEET/AIPMT papers. (On the eSaral page the actual question images couldn't be read as text, so these are built to drill the same high-yield facts.)
Malpighian tubules in cockroach are situated at the junction of: NEET favourite▸
- a) Foregut and midgut
- b) Midgut and hindgut
- c) Crop and gizzard
- d) Pharynx and oesophagus
Malpighian tubules (100–150, yellow, thin) lie at the midgut–hindgut junction and remove nitrogenous waste as uric acid → cockroach is uricotelic. (Hepatic caeca, not these, sit at the foregut–midgut junction.)
The excretory structures that functionally resemble the mammalian ureter in cockroach are: NEET favourite▸
- a) Nephridia
- b) Hepatic caeca
- c) Malpighian tubules
- d) Green glands
Malpighian tubules are the main excretory organs, so they carry out the urine-removing role analogous to the mammalian ureter. (Nephridia → earthworm; green glands → prawn.)
The number of chambers in the heart of cockroach is: NEET favourite▸
- a) 4
- b) 12
- c) 13
- d) 8
The dorsal tubular heart is differentiated into 13 funnel-shaped chambers with paired ostia. Circulation is of the open type.
Hepatic caeca in cockroach are located at the junction of foregut and midgut and their function is: NEET favourite▸
- a) Excretion of uric acid
- b) Storage of food
- c) Secretion of digestive juice
- d) Grinding food
The ring of 6–8 blind hepatic (gastric) caeca secretes digestive enzymes. Storage = crop; grinding = gizzard; excretion = Malpighian tubules.
Each compound eye of a cockroach is made of about how many ommatidia? NEET favourite▸
- a) 200
- b) 2000
- c) 100–150
- d) 13
About 2000 hexagonal ommatidia per eye produce mosaic vision — high sensitivity, low resolution, suited to nocturnal life.
The "brain" of the cockroach is represented by the: NEET favourite▸
- a) Sub-oesophageal ganglion
- b) Supra-oesophageal ganglion
- c) Last abdominal ganglion
- d) Prothoracic ganglion
The supra-oesophageal ganglion (above the oesophagus) acts as the brain and supplies nerves to the antennae and compound eyes.
In the cockroach's nervous system, the number of ganglia in thorax and abdomen respectively is: NEET favourite▸
- a) 6 and 3
- b) 3 and 6
- c) 3 and 3
- d) 2 and 8
3 ganglia in the thorax and 6 in the abdomen, joined by paired ventral connectives.
A mushroom-shaped gland in the cockroach is found in the: NEET favourite▸
- a) Female, secreting ootheca
- b) Male, as an accessory reproductive gland
- c) Both sexes, for excretion
- d) Female, storing sperm
The mushroom gland lies in the 6th–7th abdominal segments of the male and acts as an accessory reproductive gland. The ootheca-secreting gland is the female colleterial gland.
Anal styles in cockroach are: NEET favourite▸
- a) Present in both sexes
- b) Present only in females
- c) Present only in males
- d) Absent in both sexes
A pair of short, thread-like anal styles is present only in males. Anal cerci occur in both sexes (10th segment).
Each ootheca of cockroach contains approximately how many eggs?▸
- a) 6–8
- b) 9–10
- c) 14–16
- d) 100–150
One ootheca holds 14–16 eggs; a female produces about 9–10 oothecae on average. (Trap: 9–10 is the number of oothecae, not eggs.)
The blood (haemolymph) of cockroach is colourless because:▸
- a) It contains haemocyanin
- b) It lacks any respiratory pigment
- c) It carries only uric acid
- d) RBCs are nucleated
Haemolymph = colourless plasma + haemocytes, with no respiratory pigment. Oxygen is delivered directly by the tracheal system, so blood need not carry it.
The gizzard (proventriculus) of cockroach bears how many chitinous teeth?▸
- a) 6
- b) 8
- c) 10
- d) 13
The gizzard has thick circular muscles and an inner cuticle forming 6 highly chitinous teeth that grind food.
Respiration in cockroach takes place through how many pairs of spiracles?▸
- a) 8 pairs
- b) 10 pairs
- c) 12 pairs
- d) 6 pairs
Tracheae open to the outside through 10 pairs of spiracles, regulated by sphincters; gas exchange occurs by diffusion at the tracheoles.
The forewings (tegmina) of cockroach arise from the:▸
- a) Prothorax
- b) Mesothorax
- c) Metathorax
- d) First abdominal segment
Tegmina (forewings) arise from the mesothorax — opaque, leathery, protective. The transparent flight hind wings arise from the metathorax.
Number of segments in the abdomen of cockroach is:▸
- a) 8
- b) 9
- c) 10
- d) 11
The abdomen has 10 segments in both sexes.
The egg case (ootheca) of cockroach is secreted by the:▸
- a) Mushroom gland
- b) Spermatheca
- c) Colleterial gland
- d) Conglobate gland
The female colleterial glands secrete the hard protein case (ootheca). Spermatheca only stores sperm; mushroom gland is a male accessory gland.
In cockroach, the testes are located in which abdominal segments?▸
- a) 2nd–6th
- b) 4th–6th
- c) 6th–7th
- d) 9th–10th
A pair of testes lies in the 4th–6th segments. (Ovaries → 2nd–6th; mushroom gland → 6th–7th.)
The development of Periplaneta americana is:▸
- a) Holometabolous
- b) Ametabolous
- c) Paurometabolous
- d) Direct, without moulting
Paurometabolous — development through a nymphal stage (incomplete metamorphosis); nymphs resemble adults and moult ~13 times.
Bundles of sperms discharged during copulation in cockroach are called:▸
- a) Ootheca
- b) Spermatophores
- c) Ovarioles
- d) Phallomeres
Sperms are stored in seminal vesicles and glued into bundles called spermatophores. Phallomeres = male external genitalia; ovarioles = egg tubes in the ovary.
The male external genitalia of cockroach are represented by:▸
- a) Anal cerci
- b) Gonapophyses / phallomeres
- c) Ovipositor
- d) Spermatheca
Chitinous, asymmetrical gonapophyses (phallomeres) surround the male gonopore.
Besides Malpighian tubules, excretion in cockroach is also helped by:▸
- a) Fat body, nephrocytes and urecose glands
- b) Hepatic caeca and crop
- c) Salivary glands
- d) Gizzard and colon
The fat body, nephrocytes and urecose (uricose) glands assist excretion. The fat body also stores reserves — a frequently-tested dual function.
Each ovary of cockroach is made up of how many ovarian tubules (ovarioles)?▸
- a) 6
- b) 8
- c) 10
- d) 16
Each ovary is a group of 8 ovarioles, each holding a chain of developing ova.
Rapid-fire FAQs
| Question | Answer |
|---|---|
| Common name of Periplaneta americana? | American cockroach |
| Where are Malpighian tubules found? | At the midgut–hindgut junction (100–150 of them) |
| Position of ovaries in cockroach? | 2nd–6th abdominal segments |
| Segments in the cockroach abdomen? | 10 (in both sexes) |
| Type of circulatory system? | Open type; 13-chambered heart; haemolymph |
| Why uricotelic? | Excretes nitrogenous waste as uric acid |
| Why can it live a week without its head? | Most of the nervous system runs along the ventral body, not the head |
The Cockroach
Periplaneta americana
Class 11 · Structural Organisation in Animals — a complete, exam-first note. Every NCERT fact, explained in simple language, with high-yield flags, mnemonics and NEET-style PYQ practice.
Identity, habit & habitat
A cockroach is a brown-to-black insect that has quietly perfected the art of survival — so well that a famous (NCERT-backed) fact is that it can survive about a week even after its head is cut off.
Cockroaches belong to Class Insecta of Phylum Arthropoda. They are nocturnal omnivores living in damp places worldwide, and have become common house residents — which makes them serious pests and vectors of several diseases. Size ranges from about ¼ inch to 3 inches (0.6–7.6 cm). The common species studied for NEET is Periplaneta americana, with adults about 34–53 mm long; in males the wings extend beyond the tip of the abdomen.
- Common name
- American cockroach
- Scientific name
- Periplaneta americana
- Phylum
- Arthropoda
- Class
- Insecta
- Body symmetry
- Bilateral, triploblastic, segmented, coelomate
- Excretion
- Uricotelic (excretes uric acid)
Why this chapter is a guaranteed scorer
Cockroach sits inside Unit V – Structural Organisation in Plants and Animals, which carries roughly 5% weightage in NEET. Cockroach alone reliably delivers 1–2 questions per paper. The best part: questions are almost entirely direct recall of fixed anatomical facts — no reasoning traps, definite answers. Two or three focused sessions = full marks here, year after year.
| Year | Qs from cockroach | Sub-topic tested |
|---|---|---|
| 2024 | 1 | Nervous system — nerve ring & ganglia |
| 2023 | 2 | Malpighian tubules, reproductive system |
| 2022 | 1 | Digestive system — hepatic caeca |
| 2021 | 2 | Sense organs, reproductive structures |
| 2020 | 1 | External morphology — tagmata, segments |
| 2019 | 2 | Nervous system, Malpighian tubules |
| 2018 | 1 | Digestive system, gizzard function |
| 2017 | 2 | Reproductive system, oothecae |
| 2016 | 1 | Circulatory system — open type |
| 2015 | 2 | Morphology, fat body function |
External morphology
The body is segmented and divided into three distinct regions (tagmata): head, thorax and abdomen. The entire body is covered by a hard, brown chitinous exoskeleton. In each segment the exoskeleton forms hardened plates called sclerites — tergites on the dorsal (back) side and sternites on the ventral (belly) side — joined by a thin, flexible arthrodial (articular) membrane.
① Head
The head is triangular, lies at right angles to the body axis, and is formed by the fusion of 6 segments. Thanks to a flexible neck, it can move in all directions. It carries:
- A pair of compound eyes.
- A pair of thread-like antennae (sensory — monitor the environment) arising from sockets in front of the eyes.
- Biting & chewing mouthparts: labrum (upper lip), a pair of mandibles, a pair of maxillae, a labium (lower lip), and a tongue-like median lobe, the hypopharynx.
② Thorax
Made of three parts — prothorax, mesothorax, metathorax. Each thoracic segment bears one pair of walking legs (so 3 pairs total). Two pairs of wings are present:
- Forewings (tegmina) — arise from the mesothorax; opaque, dark, leathery; cover the hind wings at rest.
- Hind wings — arise from the metathorax; transparent, membranous; used in flight.
③ Abdomen
The abdomen has 10 segments in both sexes. This region is the easiest place to tell males and females apart — a classic NEET point:
| Feature | Male ♂ | Female ♀ |
|---|---|---|
| Anal styles | Present (a pair, thread-like) | Absent |
| Anal cerci (10th segment) | Present | Present (in both sexes) |
| Genital pouch | At hind end (9th–10th terga, 9th sternum) | Brood/genital pouch from 7th, 8th, 9th sterna |
| Wings | Extend beyond abdomen tip | Shorter |
Digestive system
The alimentary canal lies in the body cavity and is divided into three regions: foregut, midgut and hindgut. Trace the food's journey:
Mouth → Pharynx → Oesophagus → Crop → Gizzard (proventriculus) → Hepatic caeca → Midgut (mesenteron) → Ileum → Colon → Rectum → Anus.
- Crop — a sac-like structure for storing food.
- Gizzard / proventriculus — has thick circular muscles and a thick inner cuticle forming 6 highly chitinous "teeth" that grind food. The entire foregut is lined by cuticle.
- Hepatic (gastric) caeca — a ring of 6–8 blind tubules at the junction of foregut and midgut; they secrete digestive juice.
- Salivary glands — a pair, present near the crop, with salivary reservoirs.
Circulatory system
The cockroach has an open circulatory system — blood is not confined to vessels. Vessels are poorly developed and open into large spaces collectively called the haemocoel, where the organs are simply bathed in blood.
- The blood is called haemolymph = colourless plasma + haemocytes. It has no respiratory pigment (so it does not carry oxygen — the tracheal system does that job).
- The heart is an elongated muscular tube along the mid-dorsal line of thorax and abdomen, differentiated into 13 funnel-shaped chambers with paired ostia on either side.
- Blood from the sinuses enters the heart through the ostia and is pumped anteriorly (forward) back to the sinuses.
Respiratory system
Respiration is by a network of air tubes called tracheae, which open to the outside through 10 pairs of small holes called spiracles on the lateral sides of the body. The tracheae branch into finer tracheoles that carry oxygen directly to every tissue.
- Spiracle openings are regulated by sphincters.
- Gas exchange happens at the tracheoles by simple diffusion.
Excretory system
Excretion is performed mainly by Malpighian tubules — the most tested structure in the whole chapter.
| Feature | Detail |
|---|---|
| Number | 100–150, thin, yellow, filamentous |
| Position | At the junction of midgut & hindgut (mesenteron–ileum) |
| Lining | Glandular + ciliated cells |
| Function | Absorb nitrogenous waste from haemolymph → convert to uric acid → excreted via hindgut |
Because the final waste is uric acid, the cockroach is uricotelic. Additional excretory help comes from the fat body, nephrocytes and urecose (uricose) glands.
Nervous system & sense organs
The nervous system is a chain of fused, segmentally arranged ganglia joined by paired longitudinal connectives, running along the ventral (belly) side — this is why a cockroach survives even after losing its head: most of its nervous system is in the body, not the head.
- Ganglia: 3 in the thorax + 6 in the abdomen.
- The "brain" is the supra-oesophageal ganglion (above the oesophagus); it supplies nerves to antennae and compound eyes.
- The sub-oesophageal ganglion lies below the oesophagus; the two are linked by circum-oesophageal connectives forming a nerve ring around the oesophagus.
Sense organs & vision
Sense organs include antennae, eyes, maxillary palps, labial palps and anal cerci. The compound eyes sit on the dorsal head surface. Each eye has about 2000 hexagonal ommatidia. Many ommatidia together give many small images of one object — this is mosaic vision: more sensitivity but less resolution, ideal for the cockroach's nocturnal (night) life.
Reproductive system
Cockroaches are dioecious (sexes separate) with internal fertilisation.
Male ♂
- A pair of testes — one on each side, in the 4th–6th abdominal segments.
- Each testis → vas deferens → seminal vesicle → ejaculatory duct → male gonopore (ventral to anus).
- Mushroom-shaped gland in the 6th–7th segments = accessory reproductive gland.
- External genitalia = gonapophyses / phallomeres (chitinous, asymmetrical).
- Sperms are glued into bundles called spermatophores, discharged during copulation.
Female ♀
- A pair of ovaries in the 2nd–6th abdominal segments.
- Each ovary = group of 8 ovarian tubules (ovarioles) with chains of developing ova.
- Oviducts unite into a single median oviduct (vagina) opening into the genital chamber.
- A pair of spermatheca in the 6th segment (stores sperm).
- Colleterial glands secrete the protective egg case, the ootheca.
Ootheca
Fertilised eggs are encased in a dark reddish-to-blackish-brown capsule called an ootheca, about 8 mm (3/8") long. On average a female produces 9–10 oothecae, each containing 14–16 eggs. Oothecae are dropped/glued in cracks of high humidity near food.
Development
Development of P. americana is paurometabolous — i.e., development through a nymphal stage, with incomplete metamorphosis. The nymphs look very much like the adults. A nymph grows by moulting about 13 times to reach the adult form. The next-to-last nymphal stage has wing pads, but only adults have full wings.
The one-page fact sheet
This is the table to revise 3 times before NEET. If you can reproduce it from memory, the cockroach questions are yours.
| System / Topic | Key structure | Number / Position / Function |
|---|---|---|
| Morphology | Body regions | Head + Thorax + Abdomen; abdomen = 10 segments |
| Morphology | Legs / Wings | 3 pairs legs; tegmina (meso-), hind wings (meta-) |
| Digestive | Gizzard teeth | 6 chitinous teeth; grinds food |
| Digestive | Hepatic caeca | 6–8; foregut–midgut junction; secrete enzymes |
| Circulatory | Heart | 13 chambers; open type; ostia; haemolymph colourless |
| Respiratory | Spiracles | 10 pairs; tracheae → tracheoles; diffusion |
| Excretory | Malpighian tubules | 100–150; midgut–hindgut junction; uric acid → uricotelic |
| Nervous | Ganglia | Brain = supra-oesophageal; 3 thoracic + 6 abdominal |
| Senses | Compound eye | ~2000 ommatidia; mosaic (nocturnal) vision |
| Repro (♂) | Testes / Mushroom gland | Testes 4–6th seg; mushroom gland 6–7th seg |
| Repro (♀) | Ovaries / Ootheca | Ovaries 2–6th seg; ootheca = 14–16 eggs; 9–10 produced |
| Development | Type | Paurometabolous; ~13 moults; wings only in adult |
Most-repeated topics (2015–2024)
Ranked by how often each appeared across the last 10 NEET papers (analysis source: eSaral):
| Rank | Topic | Appeared in |
|---|---|---|
| 1 | Malpighian tubules — position, number, uricotelic | 8 / 10 yrs |
| 2 | Nervous system — supra-oesophageal ganglion, nerve ring, ventral nerve cord | 7 / 10 |
| 3 | Compound eyes & mosaic vision | 6 / 10 |
| 4 | Ootheca — structure, egg number, colleterial gland | 6 / 10 |
| 5 | Hepatic caeca — position & function | 5 / 10 |
| 6 | Body tagmata & segment count | 5 / 10 |
| 7 | Open circulatory system — 13-chambered heart, ostia | 4 / 10 |
| 8 | Fat body — excretion + storage | 4 / 10 |
| 9 | Mushroom gland — male accessory gland | 3 / 10 |
| 10 | Tracheal system — 10 pairs of spiracles | 3 / 10 |
Mnemonics & memory tricks
Mouth · Pharynx · Esophagus · Crop · Gizzard · Hepatic caeca · Midgut · Ileum · Colon · Rectum · Anus.
NEET PYQ-pattern MCQs
Tap any question to reveal the answer & explanation. Questions marked NEET favourite test facts that have repeatedly appeared in NEET/AIPMT papers. (On the eSaral page the actual question images couldn't be read as text, so these are built to drill the same high-yield facts.)
Malpighian tubules in cockroach are situated at the junction of: NEET favourite▸
- a) Foregut and midgut
- b) Midgut and hindgut
- c) Crop and gizzard
- d) Pharynx and oesophagus
Malpighian tubules (100–150, yellow, thin) lie at the midgut–hindgut junction and remove nitrogenous waste as uric acid → cockroach is uricotelic. (Hepatic caeca, not these, sit at the foregut–midgut junction.)
The excretory structures that functionally resemble the mammalian ureter in cockroach are: NEET favourite▸
- a) Nephridia
- b) Hepatic caeca
- c) Malpighian tubules
- d) Green glands
Malpighian tubules are the main excretory organs, so they carry out the urine-removing role analogous to the mammalian ureter. (Nephridia → earthworm; green glands → prawn.)
The number of chambers in the heart of cockroach is: NEET favourite▸
- a) 4
- b) 12
- c) 13
- d) 8
The dorsal tubular heart is differentiated into 13 funnel-shaped chambers with paired ostia. Circulation is of the open type.
Hepatic caeca in cockroach are located at the junction of foregut and midgut and their function is: NEET favourite▸
- a) Excretion of uric acid
- b) Storage of food
- c) Secretion of digestive juice
- d) Grinding food
The ring of 6–8 blind hepatic (gastric) caeca secretes digestive enzymes. Storage = crop; grinding = gizzard; excretion = Malpighian tubules.
Each compound eye of a cockroach is made of about how many ommatidia? NEET favourite▸
- a) 200
- b) 2000
- c) 100–150
- d) 13
About 2000 hexagonal ommatidia per eye produce mosaic vision — high sensitivity, low resolution, suited to nocturnal life.
The "brain" of the cockroach is represented by the: NEET favourite▸
- a) Sub-oesophageal ganglion
- b) Supra-oesophageal ganglion
- c) Last abdominal ganglion
- d) Prothoracic ganglion
The supra-oesophageal ganglion (above the oesophagus) acts as the brain and supplies nerves to the antennae and compound eyes.
In the cockroach's nervous system, the number of ganglia in thorax and abdomen respectively is: NEET favourite▸
- a) 6 and 3
- b) 3 and 6
- c) 3 and 3
- d) 2 and 8
3 ganglia in the thorax and 6 in the abdomen, joined by paired ventral connectives.
A mushroom-shaped gland in the cockroach is found in the: NEET favourite▸
- a) Female, secreting ootheca
- b) Male, as an accessory reproductive gland
- c) Both sexes, for excretion
- d) Female, storing sperm
The mushroom gland lies in the 6th–7th abdominal segments of the male and acts as an accessory reproductive gland. The ootheca-secreting gland is the female colleterial gland.
Anal styles in cockroach are: NEET favourite▸
- a) Present in both sexes
- b) Present only in females
- c) Present only in males
- d) Absent in both sexes
A pair of short, thread-like anal styles is present only in males. Anal cerci occur in both sexes (10th segment).
Each ootheca of cockroach contains approximately how many eggs?▸
- a) 6–8
- b) 9–10
- c) 14–16
- d) 100–150
One ootheca holds 14–16 eggs; a female produces about 9–10 oothecae on average. (Trap: 9–10 is the number of oothecae, not eggs.)
The blood (haemolymph) of cockroach is colourless because:▸
- a) It contains haemocyanin
- b) It lacks any respiratory pigment
- c) It carries only uric acid
- d) RBCs are nucleated
Haemolymph = colourless plasma + haemocytes, with no respiratory pigment. Oxygen is delivered directly by the tracheal system, so blood need not carry it.
The gizzard (proventriculus) of cockroach bears how many chitinous teeth?▸
- a) 6
- b) 8
- c) 10
- d) 13
The gizzard has thick circular muscles and an inner cuticle forming 6 highly chitinous teeth that grind food.
Respiration in cockroach takes place through how many pairs of spiracles?▸
- a) 8 pairs
- b) 10 pairs
- c) 12 pairs
- d) 6 pairs
Tracheae open to the outside through 10 pairs of spiracles, regulated by sphincters; gas exchange occurs by diffusion at the tracheoles.
The forewings (tegmina) of cockroach arise from the:▸
- a) Prothorax
- b) Mesothorax
- c) Metathorax
- d) First abdominal segment
Tegmina (forewings) arise from the mesothorax — opaque, leathery, protective. The transparent flight hind wings arise from the metathorax.
Number of segments in the abdomen of cockroach is:▸
- a) 8
- b) 9
- c) 10
- d) 11
The abdomen has 10 segments in both sexes.
The egg case (ootheca) of cockroach is secreted by the:▸
- a) Mushroom gland
- b) Spermatheca
- c) Colleterial gland
- d) Conglobate gland
The female colleterial glands secrete the hard protein case (ootheca). Spermatheca only stores sperm; mushroom gland is a male accessory gland.
In cockroach, the testes are located in which abdominal segments?▸
- a) 2nd–6th
- b) 4th–6th
- c) 6th–7th
- d) 9th–10th
A pair of testes lies in the 4th–6th segments. (Ovaries → 2nd–6th; mushroom gland → 6th–7th.)
The development of Periplaneta americana is:▸
- a) Holometabolous
- b) Ametabolous
- c) Paurometabolous
- d) Direct, without moulting
Paurometabolous — development through a nymphal stage (incomplete metamorphosis); nymphs resemble adults and moult ~13 times.
Bundles of sperms discharged during copulation in cockroach are called:▸
- a) Ootheca
- b) Spermatophores
- c) Ovarioles
- d) Phallomeres
Sperms are stored in seminal vesicles and glued into bundles called spermatophores. Phallomeres = male external genitalia; ovarioles = egg tubes in the ovary.
The male external genitalia of cockroach are represented by:▸
- a) Anal cerci
- b) Gonapophyses / phallomeres
- c) Ovipositor
- d) Spermatheca
Chitinous, asymmetrical gonapophyses (phallomeres) surround the male gonopore.
Besides Malpighian tubules, excretion in cockroach is also helped by:▸
- a) Fat body, nephrocytes and urecose glands
- b) Hepatic caeca and crop
- c) Salivary glands
- d) Gizzard and colon
The fat body, nephrocytes and urecose (uricose) glands assist excretion. The fat body also stores reserves — a frequently-tested dual function.
Each ovary of cockroach is made up of how many ovarian tubules (ovarioles)?▸
- a) 6
- b) 8
- c) 10
- d) 16
Each ovary is a group of 8 ovarioles, each holding a chain of developing ova.
Rapid-fire FAQs
| Question | Answer |
|---|---|
| Common name of Periplaneta americana? | American cockroach |
| Where are Malpighian tubules found? | At the midgut–hindgut junction (100–150 of them) |
| Position of ovaries in cockroach? | 2nd–6th abdominal segments |
| Segments in the cockroach abdomen? | 10 (in both sexes) |
| Type of circulatory system? | Open type; 13-chambered heart; haemolymph |
| Why uricotelic? | Excretes nitrogenous waste as uric acid |
| Why can it live a week without its head? | Most of the nervous system runs along the ventral body, not the head |