Question

Which one of the following is the correct statement about cockroach? (a) Anal style is present only in male cockroach. (b) Anal cerci are present only in female cockroach. (c) Each eye consists of about 1000 hexagonal ommatidia. (d) Each oothecae contain 12 to 14 eggs.

Short answer

The correct statement is: (c) Each eye consists of about 1000 hexagonal ommatidia.

Step-by-step solution

Systematically Evaluate Each Statement

Now that the characteristics mentioned in each statement are understood, the next step is to go through each option systematically and evaluate the truth of the statements. (a) Anal styles are present in both male and female cockroaches, so this statement is false. (b) Anal cerci are likewise present in both genders of cockroach, so this statement is also false. (d) A cockroach ootheca usually contains more than 14 eggs - often around 40, so this statement is false.

Identify the Correct Statement

Having evaluated all the other statements as false, it would follow that (c) Each eye consists of about 1000 hexagonal ommatidia is the remaining and true statement about cockroaches. The ommatidia are the numerous, simple eyes that make up a cockroach's compound eyes and there are about 2000 in each, though some species have only half of that number, making the statement approximately correct.

Key concepts

Ommatidia

Have you ever wondered how a cockroach sees the world around it? The answer lies in a sophisticated part of its anatomy known as ommatidia. Ommatidia are the tiny, numerous visual units that make up a cockroach's compound eyes. Imagine a mosaic of tiny lenses, each one collecting light from its own distinct portion of the visual space. With about 2000 of these hexagonally arranged lenses, the compound eye of a cockroach provides a wide angle of view and helps to detect even the smallest movements around it. This is crucial for survival, as it allows these insects to quickly evade threats.

While the human eye uses a single lens to focus light onto the retina, cockroaches and other insects with compound eyes use their ommatidia to gather visual information from a complex array of angles simultaneously. However, this type of vision does not focus on fine details but rather excels in perceiving changes and movements in the surrounding environment. This multi-lens system is not unique to cockroaches; it's shared by many insects, crustaceans, and even some types of polychaete worms.

Insect Morphology

Insect morphology is the study of the structure and form of insects. It's an essential field in understanding not only how these creatures look but also how they function and adapt to their environments. Insects like cockroaches are masterpieces of evolutionary design, with bodies that are segmented into three primary regions: the head, thorax, and abdomen.

The head houses the sensory organs and brain, while the thorax is equipped with appendages such as legs and wings. The abdomen, on the other hand, contains important components of the digestive, excretory, and reproductive systems. Additionally, details such as the presence of anal cerci, which are sensory appendages found in both male and female cockroaches, are critical for balance and environmental awareness. Insect morphology also includes the study of insect exoskeletons, which are made of a tough substance called chitin. This exoskeleton serves not only as a protective casing but also as a structure to which muscles are attached, enabling movement.

Reproductive System of Cockroach

Reproduction is a pivotal aspect of any species' survival, and in cockroaches, this process is facilitated by a complex reproductive system. Male cockroaches have a pair of testes where sperm production occurs. From these testes, the sperm travel through the vas deferens to seminal vesicles, where they are stored until mating. During copulation, males transfer a sperm packet, or spermatophore, to females.

The female reproductive system includes a pair of ovaries, where the eggs are produced. These eggs are then encased in a protective capsule known as an ootheca, which the female often carries externally until the eggs are ready to hatch. This capsule can contain a significant number of eggs; typically more than 14, debunking a common misconception. After the formation of an ootheca, it is either dropped or glued to a suitable surface where the eggs continue to develop until nymphs emerge. In understanding the reproductive system of cockroaches, we gain insight into how they can proliferate rapidly and thrive in various environments, making them resilient pests.