can anyone give me some hints for sexing rhino roaches?

[NecroNeko]

i am a newbie for roaches and recently i got a pair of rhino around 8cm. The seller said they were couples but i want to know exactly whether they are:}
can u guys kindly show me the picture of matured couples' bottom? thx:worship:

 

[Matt K]

Not to state the obvious, but:

Male rhinos have a curved protrusion on thier pronotum hence the name "rhino" roach. Females do not have this. At 8cm it should be obvious.

 

[OldHag]

http://www.arachnoboards.com/ab/showthread.php?t=54406
That thread shows differences pretty good.
You can also tell by the last segment on their undersides. They are pretty much the same as other roaches. Large last segment=female. Smaller last segment=male.