Hartz UltraGuard Flea and Tick Drops for Cats 5 lbs and under. An easy to use topical application that Kills flea Eggs and Larvae for 30 days. It also provides relief from flea populations on cats and kittens by controlling and preventing flea eggs and larvae. Adult fleas can live on your pet while also producing vast numbers of eggs which drop off your pet and develop in the surrounding environment. Kills flea eggs and larvae thereby breaking the flea life cycle.