I saw a little teenie tiny bug crawling on my dogs stomach.?

When I went to take it off, I couldn't grasp it. It is smaller than an ant, the same size in length, and thin as a hair strand. Then I saw another one. What can these little rascals be. She is utd in all her shots, and has been dewormed. Is there anything to buy that will get rid of pests on your dog?