producing sperm plugs question

"producing sperm plugs"~~`saw this in an ad,what does it mean?

It means he is ready to breed... once they are sexually mature they start to produce sperm plugs... basically, old sperm that is pushed out when you pop them.

Bruce

Thank you!

Ok, i would like to add to this, i only breed corns so far but have plans for a couple of royals next year.
Will the male only show the plugs if someone attempts to pop him?, or will you see the 'plugs' lose in the box for instance?.
if so, what would they look like?
sorry if its a silly question, but sometimes these are the sort that bug people lol.