All insects has three main body region, namely: the head, thorax and the abdomen. These main parts of an insect body functions differently from each other.
The insect head was designed primarily for sensory purposes because of the fact that the eyes and the antenna of an insect is situated on the head.
The thorax on the other hand plays a very important role in insect movement and locomotion. Appendages like legs and wing are attached to the thoracic region which enables an insect to fly and disperse.
The insect abdomen is considered to be the receptacle of the casing of the visceral organs of an insect. This is also essential in carrying out vital physiological processes such as respiration, circulation, thermoregulation, excretion, and reproduction.
Let us now examine these insect main body regions in detail.
The Insect Head
It is mentioned above that the insect head is where we find the sensory organs of the insect. Yes that’s correct. Insect’s eyes are located at the insects head.
We have two types of insect eyes namely:
Ocellus (plural: Ocelli)
The ocelli of an insect are also known as the simple eyes. The main function of the simple eye is to perceive the difference between light and darkness. The stimulation of the ocelli prompts the other receptors or sense organs to facilitate reflex response. This type of insect eyes can also perceive ultra violet lights and infrared.
The insect’s compound eyes are made up of many hexagonal honey-comb shaped structures called facets; which enable an insect to see the details of its environment such as color, depth, height and etc. Each of these facets is a cornea of a distinct eye or ommatidium which separately functions; proposed by Johannes Mueller in 1829; apposition eye for diurnal insects and superposition eyes for nocturnal insects.
The antenna of an insect serves as phonoreceptor, meaning this body part is well capable of perceiving sound waves. It can also function olfactory perceiving smell of chemicals around them. The antennae has three major parts.
- Scape – The scape is the basal segment of the insect antenna. It connects and pivot the the antennae on the head.
- Pedicel – It is situated at the middle portion of the antenna. It contains the Johnston’s organ, which is capable of perception.
- Flagellum – The flagellum is a series of smaller segments of equal size also called the clavola.
The pedicel and the flagellum are regions containing sense hairs and sensilla and special organ for olfaction and phonoreception.
Types of antenna:
Filiform - threadlike
Setaceous - setalike
(dragonflies, damselflies, cicada, leafhoppers)
Moniliform - beadlike
Serrate - sawlike
(female click beetle)
Pectinate - comblike
(male click beetle)
Lamellate - lamella like
(toy beetle, scarabaied)
(ants and bees)
Plumose- featherlike (mosquitoes)
Capitate – head like
Aristate - arista like