There are actually more species of silverfish than you might expect. Worldwide there are 120 known species. In North America alone there are eighteen silverfish species. These eighteen species can be categorized into five types: Common silverfish, Gray silverfish, Firebrat, Jumping Bristletail, and Four-lined Silverfish.
One thing to keep in mind is that not all silverfish are part of the same order. There is only one Leisma saccharina, or common silverfish, in the country. Other orders silverfish may fall into include Archaeognatha, Ctenolepisma, and Thermobia.