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Cockroach Morphology Short Notes

In this article we will discuss about the cockroach morphology

Cockroach Morphology

Cockroaches are brown or black bodied animals
Inhabiting the unhygienic and damp places
Cockroaches are nocturnal, omnivorous, cursorial and exhibit cannibalism
Cockroach can run 130 cm/sec
They also transmit various types of bacterial diseases
Adults cockroach are about 34-53 mm long with wings
Body divided into head, thorax and abdomen
Body divisible into segments and some segment fuses in adult stage
Body is covered by hard chitinous exoskeleton
Exoskeleton of chitin plates occurred in each segment
Chitin plate called sclerites
Sclerites joined each other by membrane called arthroidal membrane
- Sclerites of dorsal side – tergum or tergite
- Sclerites of lateral side – pleura or pleurites
- Sclerites of ventral side – sternum or sternite

Head

Head is triangular and hypognathous
Head is formed by fusion of six segments
Sclerites of the head joined fully and form head capsule
The head bears a pair of compound eye, a pair of antennae.
Each compound eye made up of 2000 units called ommatidia
Antennae have sensory receptors
Head bears appendages meant for biting and chewing types of mouth parts
Mouth situated in the anterior side of head which is surrounded by mouth parts

Mouth Parts Of Cockroach

A labrum (upper lip)

Broad and roughly rectangular shaped structure
Bear chemoreceptor on inner side

A pair of mandibles

Pair of hard, strong, large, dark coloured structures found one on either side
They bear pointed teeth like structure and crush the food present in between them

A pair of maxillae

Lie outside and behind the mandibles & made up of five segment
Function: cockroach pickup its food and put it in preoral cavity for chewing.
Maxillary palps also used as brush to clean antenna and wing.

A labium (lower lip)

Labium is formed by the fusion of the second pair of maxillae
It forms the broad median lower lip and has a pair of 3-segmented labial palps on either side which is bear taste receptors

Hypopharynx

A median flexible lobe acting as tongue
It bears several sensory setae

Thorax

Thorax is the middle part of the body
Thorax consists of three segments – prothorax, mesothorax and metathorax.
Each thoracic segment bears a pair of walking legs
Thorax has two pairs of wings on the dorsolateral side.
Each leg is made by 5 segments
- 1st podomere is coxa: broad and attached to the thorax. It is the most swollen segment
- 2nd podomere is trochanter: It gives viability for movement of leg
- 3rd podomere is femur: strongest part of the leg. It shows bristles.
- 4th podomere is tibia: longest part of the leg. It also bears bristles
- 5th podomere is tarsus: tarsus made up of five segments called tarsomeres and the last one is called pretarsus
Each pretarsus bears one pair of claws and large adhesive pads arolium or pulvilus.
Cockroach move on the smooth surface by the help of arolium and on rough surface with the help of claws
Tactile setae are present on each segment of legs.

Two pairs of wings present

Fore wings (tegmina or elytra)

First pair of wings arises from mesothorax
Long, narrow, leathery strong
Its cover full abdomen and cover the hind wings when at rest
In male fore wings projecting out ward from abdomen

Hind wings

Hind wings arises from metathorax
Small, broad, thin and soft
These wings help in flight
They are folded like a fan and covered by elytra while at rest.

Abdomen

Abdomen is broader than thorax and consists of 10 segments while embryo has 11 segments.
All characters of sexual dimorphism in cockroach present in abdomen
10th segment in both sexes bears a pair of small, filamentous and sensory anal cerci
Each anal cercus is made of 15 segments.
In male, in addition of anal cerci, 9th sternum bears anal style (unjointed thread like) which are absent in females
Sternum: In male 9 sternum & In female 7 sternum present
In female 7th,8th,9th sterna form a brood or genital pouch

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