described terrestrial isopod species
A 2025 review of the OniscidBase database reports more than 4,100 described terrestrial species.
Source: OniscidBase database review, 2025RYZA Reference
Terrestrial Isopod Statistics
A sourced reference on isopod diversity, classification, and fossil history for keepers, educators, and writers.
Last updated September 3, 2026
A quick reference
Terrestrial isopods are often called woodlice, pillbugs, or roly-polies. They are crustaceans, not insects, and they represent only part of the much larger Isopoda order.
The figures below separate land-dwelling isopods from the broader group where the source does. That distinction matters when comparing a bioactive culture with the diversity found in oceans and freshwater habitats.
Key isopod statistics
Updated September 3, 2026documented terrestrial isopod genera
The same 2025 review counts 568 genera across the terrestrial group commonly called woodlice.
Source: OniscidBase database review, 2025recognized terrestrial families
The family total varies by classification, so current scientific sources report a range rather than one fixed number.
Source: OniscidBase database review, 2025isopod species estimated worldwide
This broader total includes marine, freshwater, and terrestrial isopods, not only the land species kept in terrariums.
Source: NOAA Ocean Exploration, 2014years since marine isopods first appear in the fossil record
The oldest fossil record belongs to marine isopods, showing how much older the group is than its terrestrial relatives.
Source: Marine Biological Association, 2025years old for the earliest terrestrial isopod fossils
Known terrestrial fossils appear much later than the marine record, but still date to more than 100 million years ago.
Source: Marine Biological Association, 2025What the numbers mean for keepers
Isopod describes a broad crustacean group
Terrarium cultures belong to the terrestrial branch of Isopoda, often referred to as Oniscidea. The worldwide estimate includes deep-sea, shoreline, freshwater, and parasitic species too. A number about all isopods should not be used as a count of species suited to a home habitat.
Taxonomy keeps moving
Species counts change as scientists describe new animals, review older names, and refine classifications. The family range on this page is intentional: it reflects the uncertainty reported by the database review instead of pretending one total is settled forever.
Natural history is not a care chart
Broad diversity and fossil data give useful context, but a culture still needs species-specific husbandry. Use RYZA's care guides to check practical requirements for the culture you are considering, including moisture, ventilation, temperature, and feeding.
Sources and method
This page uses named public sources that report their own dates. Counts are presented as the source states them, including approximate values and classification ranges. RYZA does not estimate missing numbers or combine unlike totals.
- Gongalsky, K. B. et al., OniscidBase: A call for contributions to a global database of terrestrial isopods, Soil Organisms, 2025.
- NOAA Ocean Exploration, What is an isopod?, 2014.
- Marine Biological Association, Unfurling isopod evolution, 2025.
Cite this page
RYZA Exotics. Terrestrial Isopod Statistics. Updated September 3, 2026. Accessed from https://ryzaexotics.com/isopod-statistics.
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