Checking regular couscous is relatively easy, but if you want to check whole wheat couscous, there is so much dark matter you would not be able to spot an insect or an insect part. What is the solution?
It shouldn’t really be an issue, because if the couscous is from a decent company and it wasn’t stored for a long time it is clean and you don’t have to check it. If it is old then when you spread it out on a white surface, if there are worms, or sticky clumps, then you should not use it in any case. Regarding the dark matter , you will have to look at it carefully to tell what it is. See http://dinonline.org/Bedikat/couscous/