1) The abdomen is the third tegma of the body of periplaneta.
2) It consists of ten segments.
3) Each segment is covered by four chitinous scleirites. They are the dorsal-tergum, the ventral sternum and the two lateral pleura.
4) Tergal plates:–
- There are ten tergalplates. The eigth tergum in the male and both eigth and ninth terga in the female are not visible as they are overlapped by the seventh tergum.
- The tenth tergum extends beyond the posterior end of the body and has a deep groove in the middle of its free end.
5) Sternal plates :-
- Only nine sterna are present as the tenth sternumis absent.
- In the male nine sterna are visible whereas in the female , only seven sterna are visible.
- In female the seventh, eigth and ninth sterna together forma brood pouch. The broodpouchhas two parts the anterior – genital chamber or gynatrium and the posterior – oothecal chamber.
6) Anal cerci:-
- A pair of anal cerci are present in both males and females, at the posterior end of the abdomen.
- Anal cerci are jointed and are arise from the lateral sides of the tenth tergum.
7) Anal styles :-
- A pair of anal styles are present only in males.
- Anal styles are without joins and arise from the ninth sternum.
8) Gonapophyses :-
- The gonapophyses are small chitinous processes arising from the ninth sternum in the males and eigth and ninth sterna in the females.
- Gonapophyses are the external genital organs.
- The males have three gonapophyses. These are formed from the ninth sternum.They help in copulation. In males gonapophyses are also called as phallomeres. The three phallomeres are the ventral , left and right phallomeres.
- Females have three pairs of gonapophyses. The eighth sternum bears one pair called first basi volvulae. The ninth sternum bears two pairs called valvifers and second basivalvulae respectively.They guide the ova into ootheca . in females they also called ovipositors.
9) Genital aperture :- The genital aperture in male is present just below the anus on one of the gonapophyses and in females it is located on the eigth sternum.
10) TheAnus :– The anus is present at the posterior end of the abdomen.