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Which of the following is characteristic feature of cockroach regarding sexual dimorphism?
Anal cerci are present in BOTH males and females (on 10th segment, so not dimorphic!). Anal styles (caudal styles) are unjointed thread-like appendages found EXCLUSIVELY in males on the 9th sternite! Match Option (3) Presence of anal styles!
Male and female cockroaches () exhibit distinct external abdominal appendages:
NCERT states under Cockroach Morphology: "In both sexes, the 10th segment bears a pair of jointed filamentous structures called anal cerci. In males, genital pouch contains a pair of short, thread-like anal styles which are absent in females."
Body color (dark brown/reddish brown) and exoskeletal chitinous plates (sclerites: tergites and sternites) are general morphological features shared identically across both sexes.
Diagnose every choice: Know exactly why the right option works and why distractors fail.
Anal cerci are present on the 10th segment in both sexes; hence cannot distinguish males from females.
Neither body color nor anal cerci are sexually dimorphic.
Verbatim NCERT: unjointed anal styles are present exclusively on the 9th sternum of males and absent in females.
Hardened chitinous sclerites form the exoskeleton of all cockroaches regardless of sex.
Students frequently mix up the two terms: Cerci (found in both, 10th segment) vs. Styles (males only, 9th segment).
"In males, the 9th sternite bears a pair of short, thread-like anal styles which are absent in females. Anal cerci are present in both sexes."
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