With the rise of subfluvial, Plague, and arboreal isopod lineages, it can be easy to overlook the less-charismatic crustaceans that, despite their often cryptic nature, perform vital functions for Apterra's biosphere. As a non-monophyletic informal grouping, solitary woodlice encompass a range of niches less derived than those of other crustaceans, but in many cases this hasn't stopped them from adopting physical forms very different from typical Earthly isopods. All of them are defined primarily by what they aren't, rather than what they are: any Apterran pill bug that isn't a descendant of the Plague (Pestilarthridae), Armadillidium arborealis, or Armadillidium subfluvius is considered a solitary woodlouse. Aside from the currently declining basal detritivores, there are four major groups within this category. All lead asocial lives (plus a few non-cooperative interactions such as dermestimimid feeding frenzies), and several have independently become tolerant of dry conditions, allowing them to expand far beyond the moist, dark habitats they were once restricted to.

Castlebugs (Thyrearthridae) are the descendants of heavily armored prairie-isopods that developed sharp spines to defend against rats during the Dawn and Early Muricene. This armament has increased with time, and modern castlebugs are even better protected than their predecessors, with shells covered in needle-like protrusions that make them unpalatable to nearly all predators. They can reach over ten centimeters long and five high, and they are most commonly seen in open areas. On the woodlouse-grassland, large-bodied species like kiwizelles and terror kiwis must watch their step or risk vicious puncture wounds. The rodents of the rat-grassland are somewhat protected by their quadrupedal stance, but they aren't immune to the castlebugs' powerful bite. The main threats to Thyrearthrids are pillbirds, who've become adept at battering unsuspecting bugs against rocks or logs to break through their defenses. In fact, pillbirds specializing in eating castlebugs are among the only birds that find success on the rat-grassland. 

The Dermestemimids, already a successful group millions of years ago, have cemented themselves as Apterra's foremost corpse-cleanup service, processing deceased animals with unmatched efficiency. With their strong, serrated mandibles, all members of this family pack a wicked bite, making up for their mediocre body armor. Unlike castlebugs, carrion woodlice are extremely flexible; not only do they retain the ability to curl into a tight ball, but they can also bend backward almost ninety degrees, allowing them to more easily squirm and wedge themselves deep into their food. The Janitor Bugs (genus Sturcopellus), among the largest members of the Dermestemimidae, have begun to use their flexibility for a new purpose: they seek out piles of dung dropped by large birds or rats, which they mold into balls and roll away to a safe location. This is not for the sake of the adult janitor bug, who still feeds on freshly-killed meat, but rather for its offspring, which are born too small and underdeveloped to hold their own against fully-grown congenerics in the fierce competition that occurs around every carcass. By feeding on this hidden stash of excrement, the newly-born mancae can develop in safety. Their food will be depleted around the time they complete their fifth molt, at which point the juveniles emerge and seek out their adult diet.

Hiding among leaf litter, under a rock, or perhaps within a rotting log, Squashroaches are the masters of staying out of sight. Composing the family Pronarthridae, their exoskeletons are elastic and leathery in texture, having abandoned the thick shells of their ancestors. They are more than capable of rolling into a ball, though this is no longer their preferred means of defense; their flat profiles leave gaps along the sides even when completely curled up, and their soft bodies offer little resistance to piercing wounds (though they are incredibly resilient to crushing and blunt-force trauma). Instead, they dart away from danger with surprising velocity, their long legs propelling them at speeds greater than any other animal in their size class. In the blink of an eye, they can squeeze into holes a fraction of a centimeter wide. While normally about four millimeters thick, they can compress themselves to less than half this height when necessary. Additionally, they have impressive flexibility in the side-to-side direction. 

This is taken to extremes by the Dodecipede (Dodecipes), which possesses the normal suite of squashroach features in addition to a thin, elongated body. This permits evasive tactics beyond those possible for any other woodlouse, meaning that catching a dodecipede is nearly impossible for all but the most nimble of insectivores. This genus uses only twelve of its fourteen legs for locomotion; the rearmost pair is short, flat, and held off the ground. Positioned just below the marsupium, these are used by the female when brooding a clutch of eggs, fanning the developing embryos to provide a constant flow of oxygen. This speeds up the growth process and also increases airflow across the mother's gills (in males, the latter is the sole purpose of these limbs). As a result, dodecipede hemolymph is exceptionally well-oxygenated, facilitating their fast-paced lifestyle. Certain docecipedes have even evolved a form of mutualistic prosocial behavior with other highly active isopods like Plague swarms, though they still have no attachments to members of their own species.