Segments In the abdomen, nine segments are visible In the abdomen, seven segments are visible . Anal styles Present Absent . Terga th tergum covers th tergum th tergum covers th and th terga . Brood pouch Absent Present .
Antenna Longer in length Shorter in length . Wings Extends beyond the tip of abdomen Extends up to the end of abdomen XI Std Biology-Zoology Chapter- Respiratory System The respiratory system of cockroach is well developed compared with other terrestrial insects (Figure . ). Branched tubes known as trachea open through pairs of small holes called spiracles or stigmata, present on the lateral side of the body.
Terminal branches of tracheal tubes are called tracheoles which carry oxygen to the entire body. The spiracles open and close by valves regulated by sphincter or spiracular muscles . Each tracheole is filled with a watery fluid through which exchange of gases takes place. During high muscular activity, a part of the fluid is drawn into the tissues to enable more oxygen intake and rapid diffusion.
The passage of air in the tracheal system is: SPIRACLES TRACHEA TISSUES TRACHEOLES Circulatory System Periplaneta has an open type of circulatory system (Figure . ) Blood vessels are poorly developed and opens into the haemocoel in which the blood or haemolymph flows freely. Visceral organs located in the haemocoel are bathed in blood. The haemolymph is colourless and consists of plasma and haemocytes which are ‘phagocytic’ in nature.
Heart is an elongated tube with muscular wall lying mid dorsally beneath the thorax. The heart consists of chambers with ostia on either side. The blood from the sinuses enters the heart through the ostia and is pumped anteriorly to sinuses again. The triangular muscles that are responsible for blood circulation in the cockroach are called alary muscles ( pairs).
One pair of these muscles is found in each segment on either side of the heart. In cockroach, there is an accessory pulsatile vesicle at the base of each antenna which also pumps blood. Figure . Periplaneta americana