explain in brief external characters of cockroach with figure .
- Brown or black-bodied animals.
- Size ranges from 0.6 cm to 7.6 cm
- Nocturnal; omnivores; live in damp places
- Have long antennae; flat extension of upper body wall that conceals the head
- Serious pests and vectors of several diseases
Morphology
- Adults 34−53 mm long; wings extend beyond the tip of the abdomen in males
- Body segmented; covered by chitinous exoskeleton (brown-coloured)
- At each segment, the exoskeleton has sclerites (hardened plates). Sclerites are called tergites dorsally and sternites ventrally.
- Sclerites are joined by arthrodial membrane (thin and flexible articular membrane)
Head
- Triangular shape
- Lies anteriorly at right angles to the body axis
- Formed by the fusion of 6 segments
- Shows great mobility in all directions due to a flexible neck
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Head capsule contains:
- A pair of thread-like antennae (sensory)
- A pair of compound eyes
- Biting and chewing type of mouthparts are formed by appendages present on the anterior part of the head.
- Tongue (hypopharynx) lies within the cavity enclosed by the mouth parts.
Thorax
Abdomen
- Present in both males and females; contains 10 segments
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In females:
- 7th sternum; boat-shaped
- The 7th, 8th and 9th sterna form the genital pouch (brood).
- Anterior part of genital pouch contains gonopore, spermathecal pores and collateral glands.
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In males:
- Genital pouch lies at the hind part of the abdomen
- Genital pouch is bounded dorsally by the 9th and 10th terga, and ventrally by the 9th sternum.
- Genital pouch contains dorsal anus, ventral male genital pore and gonapophysis.
- Bear a pair of short, thread-like anal styles which are not present in females
- In both sexes, the 10th segment has a pair of jointed, filamentous anal cerci.