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Isopod Pill Bug and Sow Bug Care

You can buy a variety of live pill bugs and sow bugs through our online store. Pillbugs and sowbugs are terrestrial (land) crustaceans in the taxonomic order called isopods (isopoda). Many of the species that live in backyards in the United States are originally from Europe. They are considered moderately beneficial in the sense they help break down leaves and other plant and animal remains into soil. They can occasionally become pests of greenhouses (which are unnaturally plant-rich and predator-free).

Care: Unlike many other pet bugs, isopods mature before they reach their maximum or ultimate size. They are capable of producing offspring by the time they are half grown. Cultures can easily balloon with minimal care. Keep their habitat relatively moist or humid. They enjoy having a piece of bark to hide in during the day. Many keepers provide them with egg cartons as these wick up a bit of moisture in the cage and remain moist. As omnivores they will eat bits of dog or cat food, bits of fruit and vegetable, or simply dried leaves and mosses from your backyard.

Isopods are often employed as decomposers within the pet bug, frog or reptile terrarium. Many hobbyists, from tarantula keepers, to roach and stick-insect keepers stock their cages with isopods which conveniently feed on frass (poop), leftover bits of feeder or prey insects, and pretty much anything else on or in the substrate. In this way they are often referred to as janitors. Through these clean up crew duties they go a long way to prevent the establishment of many other cage "pests" like mites and fungus gnats, as well as mold. Like a rainforest with various tiers from the upper canopy to the ground level and even slightly below it, the captive habitat can become a multi-storied, natural display with the simple introduction of these beneficial cohabitants to the cages of our other pets. 

When isopods molt, they split their exoskeleton down the middle, shedding half at a time, rather than in a single piece like other familiar arthropods. The video below documents this event.

What are the differences between pill bugs and sow bugs? The most obvious difference is that pill bugs (Armadillidium spp.) can roll themselves up into tightly closed balls. Their plated segments are thick and fit together to make a perfect sphere, thereby protecting their softer underside. Sowbugs, on the other hand, are unable to roll themselves into balls. They look very similar to pill bugs, but tend to have a flatter, less hemispherical, appearance.

We have two familiar species of pills bugs in the US. Armadillidium vulgare is the larger of the two, and the dorsal segments tend to be glossy. Larger individuals of A. vulgare (older) often exhibit yellow or greenish spotting which occurs mainly down the middle of the segments. The other species we usually encounter is Armadillidium nasatum. These are smaller and tend to have a pattern of very pale green to gray spots running through the middle and along the sides of the segments. A. nasatum is also less glossy, if at all.

Sow bugs are more diverse, including several different taxonomic genera.
Porcellio species sowbugs are the most familiar. Porcellio scaber is the most common and describes our most common species referred to as the gray sow bug. This same species comes in several color forms. In much the same way that different breeds of dog or cat are available in the mammalian pet trades, Porcellio scaber have been isolated into orange and other color forms. A good article that discusses some of the genetics at play can be found here.

Another common sow bug available in the hobby is Oniscus asellus. These are sometimes called skirted isopods because their segments have little extensions protruding along the perimeter of the body. Mature O. asellus have much thicker cuticles (shells) than Porcellio spp. do. This thickness, along with the rigid "skirting" makes them difficult mouthfuls for predators. Oniscus asellus are widespread in US metropolitan areas, as are the other species mentioned so far on this page. This particular species has more of a salt and pepper coloration and a glossy sheen. Occasionally, older individuals will exhibit beautiful, metallic flecks of green and yellow in sunlight or other bright light. Oniscus asellus is about 33% larger than Porcellio scaber.

A few other species proliferate in the hobby including some known as dwarf isopods or dwarf sowbugs. These other species are exotics which have not managed to establish in the US (they don't live here), like the aforementioned species. The reason for this is probably as simple as "they can't". These species originate in the amphibian hobby as feeder bugs. Sometimes called white isopods or dwarf white isopods, or even dwarf white sowbugs, Trichorhina tomentosa are an increasingly popular feeder species. The details of their anatomy are microscopic at first, and even the largest individuals barely reach 3mm. Similarly, jungle micropods, a cute name for micro isopods, reach 2mm at most. Both of these species, and a few others, are common feeders for poison arrow dart frogs and other young or even mature amphibians and reptiles. In a pinch they are also accepted by young tarantulas and mantises, especially the softer-bodied isopods.

Jungle Micropod Dwarf IsopodDwarf White Micropod (Isopod)
(digital microscope photos courtesy of Ryan Eide)