Extension Communications
Extension 4-H Youth Building
Ames, Iowa 50011-3630
(515) 294-9915
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Extension Communications |
11/1/04
Contacts:
Donald R. Lewis, Extension Entomologist, (515) 294-1101, drlewis@iastate.edu
Del Marks, Continuing Education and Communication Services, (515) 294-9807,
delmarks@iastate.edu
Garden column for the week of Nov. 5, 2004
Garden Recyclers
By Donald R. Lewis
Extension Entomologist
Iowa State University
Quick! Name an animal that is a crustacean.
If you remember your biology class you probably thought of large, edible crustaceans such as lobsters, shrimp, crayfish and crabs. What most of us have forgotten is that there are millions of tiny crustaceans that are important links in the aquatic food chain - animals that are eaten by bigger animals, and so on up the line. The name crustacean, by the way, refers to the crust like exoskeleton or shell on the outside of these animals.
Now, name a terrestrial crustacean.
This one is harder. It was easy to remember lobsters and their relatives that live in both salt and seawater. Less understood is the common and frequently abundant lobster-relative that lives right under our noses in the garden and landscape. Ok, so more accurately they live right under our mulch, but we're getting ahead of the story.
The answer to that second question is - 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. A few occur in fresh water, but the ones you see every year in the garden are perfectly at home on land. I'm sure you've seen this common, garden-variety sowbug. You usually find them under mulch, dead leaves, rocks, boards, grass clippings and other debris on damp ground. They survive only where there is moisture because they function similar to their aquatic cousins. That is they breathe through gills and eat decaying vegetable matter.
Sowbugs are flat, elongate-oval in shape and up to 3/4 inch in length. They vary from brown to slate gray to almost black. Their distinctive appearance comes from the hard, armor-like, overlapping plates on the top of each body segment that make them 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.
Active at night
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. They stay close to the ground, and finally, 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. If they bother you, you might try to thin the herd by removing hiding places such as piles of leaves, grass clippings, fallen fruit, boards, stones and other debris.
Sowbugs can be annoying by crawling indoors and wandering around briefly through the basement, first floor level or garage. Most die quickly because of the dryness. Sowbugs are harmless. They do not bite, sting or carry diseases nor can they damage structures, fabrics or household possessions. They are simply a nuisance because of their presence. Seal cracks and openings in the foundation wall, around doors, and around basement windows to slow invasion. 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.
In the end, sowbugs are more interesting and beneficial than they are harmful. Controls in the home and landscape are not necessary. In fact, reducing pesticide use has among its many benefits, preservation of sowbugs, our terrestrial crustacean.
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ml: isugarden