Hint: Sexual dimorphism is the condition having different characteristics in male and female sex. The characteristics which are found in male cockroaches should be noticed carefully for distinguishing male cockroaches from female cockroaches.
> Option A - The forewings are also known as tegmina. They are darker in colour. Tegmina are used to cover the hind wings during resting conditions. Forewings are found in both male and females. Which is an incorrect option.
> Option B - The boat shaped sternum is present on 7th abdominal segments in male and female cockroaches. Which is an incorrect option.
> Option C - Anal cerci are found at the 10th segment in male and female cockroaches. These are two in number and detect vibrations. Which is an incorrect option.
Option D - Male cockroaches are distinguished from female cockroaches via anal styles. Anal styles are also known as caudal styles. The anal styles are present at the 9th sternites. Anal styles are found in male cockroaches only. These are essential for motion detectors in males. Which is the correct option.
Hence, The correct answer is option (D).
Note: The following features can used to distinguish male cockroaches from female cockroaches:
- Male cockroaches are smaller than female cockroaches.
- Male cockroaches have slender abdomens as compared to females.
- Anal styles are found in males. Whereas female don’t have anal styles.
- The sternum of mesothorax is not bifurcated in males, and in females the sternum of mesothorax is bifid.
- The antennae of male cockroaches are smaller than those of the females.