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

• 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

• In females:

  • 7^th sternum; boat-shaped
  • The 7^th, 8^th and 9^th sterna form the genital pouch (brood).
  • Anterior part of genital pouch contains gonopore, spermathecal pores and collateral glands.

• In males:

  • Genital pouch lies at the hind part of the abdomen
  • Genital pouch is bounded dorsally by the 9^th and 10^th terga, and ventrally by the 9^th 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 10^th segment has a pair of jointed, filamentous anal cerci.