Fleas

    Fleas are small (1/8 of an inch), laterally flattened, brown bugs that jump and move rapidly, so they can't be seen or caught. But even though you can't see a flea on your dog, you can tell one is there by the dried blood excreted from the flea, and the black, cinder-like excreta that the flea deposits. You can also tell if your dog is scratching and biting a certain spot. 
    They are mostly found in grassy lawns, wooden areas, or any other place that inhabits lots of animals. And once the flea is on your dog and your dog moves to the house, it will start laying eggs  in the bedding, floor cracks, and dirt/sandy spots of your house. Some people have tried removing their dog from the house, thinking the fleas would go away. But there would still be larvae, eggs, and fleas hidden about the house, and although they prefer to suck animal blood, they will start going after human blood. 
    A Corgi's reaction to flea bites is usually very mild, but be careful, because some Corgis are hypersensitive to flea saliva and can suffer severe skin reactions, resulting in hot spots. But whichever reaction your dog has to fleas, remember, the flea could be transmitting Tape Worm, so check your dog to see if it has the initial symptoms (and go to the vet). 
    To prevent your dog from getting fleas, you could give your dog flea collars, flea powders, or more recommended, daily/monthly flea medication. You could also use Vapona pesticide resin strips to hang around a kennel, if there are many dogs.
    To get rid of fleas, give your dog a nice long wash-shampoo-scrub, then comb your dog out (this is especially easy for the straight-haired Corgis) until you think you've got all the fleas.  You could dust your dog with gammexane powder or pulvex to get rid of fleas. If you do so, make sure to apply around the head, neck, ears, and down the back of your dog. But remember, your dog isn't rid of fleas until your house is. You should vacuum your house thoroughly, and use flea bombs or sprays. You could also pour on diatomaceous earth that would destroy the fleas' exoskeleton.