The Charming Pill Bug As cute as anything found under a log, pill bugs, or roly-polies, are often the first “bugs” a child invites to play. My brother and I spent many hours in Canarsie poking them into little balls and rolling them around at the bottom of bottles, impatiently waiting for them to unfurl. Pill bugs are gentle, completely harmless creatures, and are often a child’s first invitation to nature in the city.
Terrestrial crustaceans, pill bugs (Armadillidium vulgare) are more closely related to crabs and crayfish than to any of their insect neighbors. They breathe through gills, which must be kept moist. Consequently, the clay pot on your porch — cool and damp with transpiration on the hottest summer days — is the perfect place to begin a search for one. An old wooden board rotting in an abandoned lot is another good starting point; there probably isn’t an abandoned lot in all of New York City that doesn’t have a few boards and bugs in residence.
But if these targets don’t produce, leaving a fragrant fruit rind, like a cantaloupe’s, face down in a shady spot for a day or two usually turns the trick.
With no enlarged eyespots, no claws and no mandibles, pill bugs don’t even pretend to look menacing. Their one defense — “conglobation,” or rolling into an armored little ball — is actually rather endearing. Countless children have learned to handle creepy crawlies through contact with roly-polies. These gentle creatures have some odd physical attributes, and some even stranger habits, that might particularly tickle the interest of a potty-minded child.
For one, pill bugs do not urinate and have a unique tolerance for waste products such as ammonia in their system. Ammonia and other waste fluids are exuded as gas through tiny pores in their shells. Pill bugs also make interesting use of their own solid wastes, practicing “coprophagy” — that is, they eat their own fecal matter. It is thought that this habit evolved to allow retention of hard-to-find copper. Pill bugs do not have iron-based hemoglobin as mammals do; rather, their blood contains hemocyanin, which relies on copper for oxygen transport. The animals are literally blue-bloods — heralding from an ancient lineage, to be sure, but their blood is light blue when oxygenated.
Another oddity for the child in all of us: Though pill bugs can drink water traditionally — that is, through their mouths — they can also absorb water through tubelike structures, called uropods, at their other ends. Pressing these against wet surfaces, the animals can absorb fluids directly into their anus through capillary action.
Female pill bugs carry their fertilized eggs in a marsupium — a brood pouch located on their underside. Their young are entirely independent upon hatching and are relatively long-lived, as arthropods go; they have been known to survive upward of two to three years in captivity, happily feeding on decaying plant and animal matter. They are a very useful (and unpaid) part of New York City’s cleanup crew.