Every tegmina of a cockroach has sclerites which are analogous to the bones of humans.

Every abdominal segment of cockroach consists of two lateral sclerite plates called pleura along with a dorsal terga and a ventral sterna. But what will be the case with the last body segment where 10th sternum is absent?

I mean will, there be any pleuron in the tenth segment because, following our textbook, pleura serve for articulation among sterna and terga and also spiracles are present in the first eight abdominal segments but the 10th sternum is absent in Periplaneta americana.

Actually there is no evidence of the presence of any pleurons in the last segment in our text book.

Moreover, there are no abdominal spiracles in the 9th and 10th segments so there is no particular reason to say that pleura are present in the 9th and 10th segments as well.


1 Answer 1


Tergal plates:

There are ten tergal plates. The $8^{th}$ tergum in the male and both $8^{th}$ and $9^{th}$ terga in the female are not visible as they are overlapped by the $7^{th}$ tergum.

The $10^{th}$ tergum extends beyond the posterior end of the body and has a deep groove in the middle of its free end.

Sternal plates:

Only nine sterna are present as the $10^{th}$ sternum is absent. In the male, nine sterna are visible whereas in the female, only seven sterna are visible.

In females, the $7^{th}$, $8^{th}$ and $9^{th}$ sterna together forma brood pouch. The brood pouch has two parts: the anterior – genital chamber or gynatrium and the posterior – gothecal chamber.

(source: lander.edu)

(source: lander.edu)

(source: biologydiscussion.com)




Youtube links for Cockroach dissection:

  • $\begingroup$ my question was about the presence or absence or lateral pleurites in the 8th and 9th body segments of a cockroach and your answers does'nt says anything about those and more over the cockroach species which i am studying about is periplaneta americana $\endgroup$ Jul 19, 2014 at 1:05
  • $\begingroup$ i am asking about the pleurites not about tergites and sternites. i too know about the sternal plates and tergal plates in abdomen but the description of pleurites or pleura is not so elaborate in our textbook $\endgroup$ Jul 21, 2014 at 12:30
  • 2
    $\begingroup$ No, The $10^{th}$ tergum extends beyond the posterior end of the body and has a deep groove in the middle of its free end.. because of this they lack the pleura as the upper structure directly comes down. You can check if you cut a cockroach. $\endgroup$ Jul 21, 2014 at 12:38
  • $\begingroup$ you seem to be right in this context but the ting is that we do not have dissection of a cockroach in our syllabus this year while it was included untill the last 32 years $\endgroup$ Jul 21, 2014 at 12:41
  • $\begingroup$ what would be the case of 9th abdominal segment?? $\endgroup$ Jul 21, 2014 at 12:44

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