Tiny, about 1/12 to 1/6 inches in length, dark reddish brown, flattened appearance (which allows them to pass easily between animal hairs). They have 4 life stages: egg, larva, pupa and biting adult. Fleas are parasites, they live on warm-blooded animals and can bite up to 400 times a day (consuming 15x their own body weight in blood). Their saliva is an allergen that can cause allergic reactions in pets and humans. Flea bites cause painful, itchy red bumps. They can jump as high as 8 inches (150 times their own height) in either direction. Female fleas can lay up to 50 eggs per day, quickly resulting in a full blown flea infestation. Protecting your pets with a monthly flea treatment is essential in flea control especially since fleas can transfer tapeworms, spread bacterial disease and cause anemia in your pets. The good news is, new veterinary-grade products not only kill adult fleas but prevent young fleas from maturing, therfore resulting in no more eggs. Additinal prevention tips include: 1) Wash pet bedding often or replace. 2) Vacuume frequently and always remember to throw the vacuum bag away, seal in tightly. 3) If your pet lives ouside where fleas are plentiful, you will need to treat the yard as well. 4) in severe infestations, contact a professional Pest Control company for treatment options.