Since most terrestrial insects are uricotelic, I assume that silverfish are, although I don’t know this for certain. Uricotelic organisms release their nitrogenous waste as uric acid. Birds, lizards, and snakes are also uricotelic. The nitrogenous waste is produced chiefly from protein metabolism in the body and also from nucleic acid breakdown.
Humans are ureotelic because the main nitrogenous waste in our urine is urea. Other mammals, adult amphibians, and cartilaginous fish (such as sharks and rays) are additional examples of ureotelic organisms.
Ammonotelic creatures release their nitrogenous waste as ammonia. These include most bony fish, many aquatic invertebrates, and amphibian larvae. Bony fish in the ocean may release urea as well as ammonia, however.
Ammonia is toxic and must be diluted in lots of water while it’s in the body. Urea is less toxic and requires less dilution. Uric acid is the least toxic of the three most common forms of nitrogenous waste and requires the least amount of dilution. The waste is often released as a paste instead of a liquid.
It should be noted that some animals release nitrogenous waste predominantly in one form and to a lesser extent in another one. This observation applies to both humans and fish. Classifying the animal in one of the above categories, as is often done, may give the wrong impression.