Wormed and flead my dog about 4 weeks ago. I used Frontline. Haven't seen a flea since, no scratching biting then a couple of nights ago one caught my eye on his back end under his tail. So after struggling to get the b@st*rd under the dogs short coat and killing it, found another 2 all adult ones. I thought it was weird the way the 3 where all near the surface at once. Since then haven't seen another. I have got more Frontline here, should I get some more on him? Or should the last lot still be in his system and should kill anyway ?