Hello, Melissa and welcome to Just Answer.
I'm sorry you found these bugs on Pywacket.
From your description, these sound like flea larvae, and even if Pywacket doesn't spend any time outside, fleas can be brought into the house on humans' pantlegs or shoes. It's also possible that these are some type of mite, so an evaluation by a vet in person, would be advisable at this time. Also try to put some of these bugs into a ziploc bag to bring to the vet for analysis. If Pywacket is not acting itchy, that's great, but not all cats act itchy with certain types of external parasites. Cats who are allergic to the fleas' saliva will have this itching reaction. http://www.cat-world.com.au/common-cat-parasites
For the moment, comb Pywacket with a fine-toothed stainless steel flea comb and have a cup prepared (tall plastic disposable drinking cup) filled with warm water and a drop or two of regular blue Dawn dishwashing liquid (or any brand you have in the house that cuts grease); comb him and dip the comb immediately into the cup. See if any fleas come out and whatever gets caught in the comb will be immediately killed by the water/dishwashing liquid. Dip the comb into another tall cup with only warm water--no dishwashing liquid, then comb again; continue this until nothing more comes out on the comb.
Also, part his fur and check Pywacket's skin for any redness or irritation so you can report this to the vet.
Once he's seen in person, the vet will advise if he can be started on a monthly flea treatment like Advantage, Frontline or Revolution (only ones sold by the vet are recommended--the ones sold in grocery stores or pet supply stores, like Hartz, are very dangerous (sometimes fatal) to a cat's health, so please don't ever use those). Depending on your location, sometimes Frontline is sold in pet supply stores, but make sure you use the correct dosage, according to Pywacket's weight.
Because he's a senior cat, it's necessary to check with the vet to make sure he doesn't have a weakened immune system or any underlying medical conditions which would make it difficult for him to tolerate a flea or mite treatment.
It's also important to treat your home and outside areas for fleas. Vacuum thoroughly and dispose of the vacuum bag, wrapped in plastic, outside, immediately. Wash any bedding in hot water with detergent, and throw out anything not washable. Hiring a professional exterminator who specializes in fleas, like Fleabusters, is a good idea; they will treat your home and the outside areas. http://fleabusters.com/
I hope all will be well with Pywacket! (Btw, LOVE his name--I'm also a Bell, Book and Candle fan!
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