Question

Ocelli or fenestrae of cockroach take part in
A. Sight
B. Perception of temperature
C. Perception of light
D. Perception of humidity

Answer 1

Hint: Cockroaches are known to exist in a variety of habitats ranging from the dark areas to minimal lighting areas. The body of cockroaches bears several receptors which help them to survive in these areas and perceive different types of stimuli such as touch, smell and changes in the environment.

Complete answer:
The cockroaches are sensitive insects and are able to see in dimly lit conditions. The adaptation in the sensation of ranges of light is due to the fact the cockroaches are nocturnal creatures and are active during the night.

The eyes in cockroaches are in the form of compound eyes. The compound eye present on the either side of the head, consists of numerous subunits or eye units. These units are known as the ommatidium. The ommatidium consists of lenses and cells that help to perceive the light. Each ommatidium produces images of the objects as a result the vision in cockroaches appear in the form of mosaic images. The mosaic images are formed by repeated light and dark points.

In cockroaches, other types of eyes are also present in addition to the compound eye. These eyes are known as simple eyes or the ocelli. The ocelli are the type of photoreceptors that are present in the cockroaches and works to perceive the light conditions. The ocelli are neither related to the pictorial vision but they are associated with the sensation of light.

The ocelli consists of only one lens and contains disorderly packed retina. The focal point of the ocular lens is present behind the retina and as a result the ocelli are not able to form an image. The sensation of light functions in many ways such as sensors for ambient light intensity and the related information is conveyed to different parts of the sensory and nervous system. The main function of the ocelli is detection of subtle changes of light intensity and helps in the orientation of the organism.

Hence, The correct answer is option (C).

Note: The ocelli are the simple eyes that are present in cockroaches. The ocelli are not related to formation of images but are responsible for perception of light. They are organs which helps the organism that can focus on the intensity of light on the retina. It is used in the process of navigation by detecting the polarised light.