Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
1/18/99
Contacts:
Donald Lewis, Extension Entomology, (515) 294-1101
Elaine Edwards, Extension Communication Systems, (515)
294-5168
Yard and Garden Column for the Week Beginning Jan. 22
Garden Good Guys
By Donald R. Lewis
Extension Entomologist
Iowa State University Extension
What hides in your garden, looks like a tiny armadillo and is closely related to the lobsters?
Give up? The sowbug.
There are many different species of sowbugs and most of the ones in the world live in the oceans as scavengers among the seaweed or as parasites on fish. The common, garden variety sowbug, however, is at home in the moist environments of your landscape --- under mulch, dead leaves, rocks, boards, grass clippings and other debris on damp ground. In these tiny, moist habitats, the sowbugs can live as they do in the water, breathing through gills and feeding on decaying vegetable matter.
Sowbugs are elongate-oval in shape and up to 3/4 inch in length. They are brownish, slate gray or almost black. Their distinctive appearance comes from the hard, armor-like, overlapping plates on the top of each body segment that make them vaguely resemble little armadillos. Sowbugs have no wings but they do possess well-developed eyes, two pairs of antennae and seven pairs of legs.
Some sowbugs are called pillbugs or 'roly-polies.' These are slate gray in color and owe their name to the ability to roll up into a tight ball when disturbed.
Landlocked, Nocturnal Crustaceans
The closest relatives of the sowbugs are other crustaceans such as lobsters, crayfish, crabs, shrimp and barnacles. Crustaceans are a large and varied group of arthropods, but almost all of them live in the water (oceans or fresh water). Adapting from this group to live on land was a major accomplishment.
Sowbugs use several 'tricks' to obtain and conserve moisture. One is they spend almost all their time in damp, dark cracks and crevices where moisture is abundant and where they will be protected from drying winds and sunshine. They generally cluster in masses to reduce water loss and they are primarily active at night when the humidity is higher and they can move about without desiccating.
Reproducing on dry land takes another special adaptation. The female sowbugs have a water-filled brood pouch on the underside of the body. Eggs are incubated inside the pouch until they hatch. The female then continues to carry the pale white offspring for six to eight weeks until they are able to take care of themselves. When the young leave the pouch, they begin feeding and growing. The young resemble the adults except they are smaller and lighter in color.
Sowbugs are cold-blooded and therefore inactive in the winter. With the arrival of spring, their activity increases and they remain active all summer.
There may be one to two generations of sowbugs each summer. Individuals live up to three years depending on weather conditions.
More Beneficial Than Harmful
Sowbugs eat decaying leaf litter and vegetable matter. Thus they are some of nature's best recyclers. They break up decaying plant matter and help speed the return of the nutrients to the ecosystem.
On occasion, sowbugs may feed on the tender tips of young plants. Such damage is more significant in the greenhouse than in the garden.
Sowbugs are annoying when they crawl indoors and wander briefly through the basement, first floor level or garage. They are harmless, however. They do not bite, sting or carry diseases nor do they damage structures, fabrics or household possessions. They are simply a nuisance because of their presence.
Those unfortunates that do wander into homes usually die in a few days unless they find a moist place near a leaky pipe or in a damp basement, bathroom or laundry room. They are unlikely to ever thrive or reproduce indoors unless a longstanding moisture problem with decaying organic matter is allowed to continue.
Sowbug migration at night or after a heavy rain may bring annoying, large numbers out onto the sidewalk or driveway. And finally, some may crawl into swimming pools and drown, causing complaints.
But in the end, sowbugs are more interesting and beneficial than they are harmful. Controls in the landscape are unnecessary and reducing pesticide use has among its many benefits, preservation of sowbugs.
For household invaders, remove hiding places such as piles of leaves, grass clippings, fallen fruit, pet droppings, boxes, boards, stones and other debris from against the foundation. Repair and seal cracks and openings in the foundation wall and around doors and basement windows. Sprays are not needed indoors. Vacuum or sweep up sowbugs inside the house and discard them back outside where they can do the most good.
ml: isugarden
Extension programs are available to all without regard to race, color, national origin, religion, sex, age, or disability.