Question

The gynovalvular plates in the female are a modification of
A. 7th tergum
B. 7th sternum
C. 8th tergum
D. 8th sternum

Answer 1

The cockroaches belong to the class Insecta and phylum Arthropoda. They are nocturnal omnivores types of insects that live mostly in damp places all over the world.

Complete Answer:
The cockroach has a segmented body that is divided into three different parts- head, thorax, and abdomen. The male reproductive system of Periplaneta consists of a pair of testes, a pair of vasa deferentia, and ejaculatory duct, a pair of seminal vesicles, a mushroom-shaped gland, and a phallic gland.

Let us analyse each option to find out the correct answer.
Option A: The body of an arthropod like a cockroach is covered by an exoskeleton called sclerites. The exoskeleton (sclerites) on the dorsal surface is known as tergum. Therefore, this is an incorrect option.

Option B: Arthropods have segmented bodies. The 7th sternum of a female cockroach encloses a big space, called the oothecal chamber or gynovalvular plates where ootheca is formed. The 7th sternite is produced backwards into two large oval gynovalvular plates or apical lobes. Therefore, this is the correct option.

Option C: The abdomen in a cockroach is narrow and long. Anal styles are present. Brood pouch is present in between 9th and 10th terga and 9th sterna. The 8th tergum is covered by the 7th tergum. Only nine sterna are visible. Nine terga are visible in the male cockroach. Therefore, this is an incorrect option.

Option D: The 7th sternum of a female cockroach encloses a big space, called the oothecal chamber or gynovalvular plates where ootheca is formed. Therefore, this is an incorrect option.

Hence the correct answer is option B.

Note: Each abdominal segment is covered with 4 sclerites: dorsal tergum, ventral sternum and two lateral pleura. Sclerites are nothing but hardened plates which are joined to each other by a flexible and thin arthrodial membrane.