I tried using a wet cotton bud but it avoided it, I poured water into a small bottle cap but it still would not drink.Then it shrivelled up and died.What could be the cause of it?
We need a little bit more information if anybody is going to have a decent shot at helping you.
How old was your mantid? Did it ever eat? How long had it been since its previous meal?
It sounds like it was too weak to eat at the end there. This might mean that you missed a few feedings and that by the time you noticed it was hungry, it was too late. Mantids are usually pretty voracious eaters!