Cockroach Morphology Short Notes | Free Biology 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