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NatureSpeak Articles

Sowbugs — bugs, boats, and ballast

The creepy crawly critters that chose to spend the winter under my woodpile got a real bonus this year. What with the balmy El Nino February and the pineapple express that turned March and April into a sodden spring, the fireplace didn't get much use. It was early May before I gathered up the bottom logs and forced the sowbugs and other many-legged seasonal squatters to find other accommodation.

Sowbugs (sometimes called woodlice) are not really bugs at all but crustaceans, or more specifically isopods. They are more closely related to lobsters and crabs than to anything in the insect world.

About the size and shape of half a pistachio shell, their grey, segmented carapace conceals everything but a pair of tiny antenna, the only obvious distinction between front and back. From above they seem to glide haphazardly about without benefit of legs – like tiny slow-moving robots on hidden wheels. Turn one over and their seven pairs of hidden legs appear to fill the entire carapace. There hardly seems room for anything else, but hidden among their other vital organs is a set of gills.

The common B.C. sowbug ( Oniscus asellus ) is truly a marine organism that has adapted to life on shore. Unlike insects which breathe through trachae along the sides of their bodies, O. asellushas no breathing apparatus other than gills which must be kept perpetually moist in order to absorb oxygen from the air. Hence their chosen habitat, under dank, mouldering pieces of wood in the ever-sodden rainforest. So important is water to their very breath of life that they have perfected the facility to drink from either end of their bodies, or if the need is urgent, to sip simultaneously with both mouth and anus.

Their chosen food is decaying plant and animal debris. And since this is not in great demand by anything else sowbugs are pretty much free to go about their dank lives without competition from other creatures or interference from human gardeners.

The females carry their eggs in a brood pouch underneath their bodies and, after hatching, the young remain in the pouch for several weeks before striking out on their own. They require about a year to become fully grown and have a life span of up to three years.

As though all this was not enough to distinguish the sowbug as a truly adaptable pioneer it actually migrated to North America from Europe long before the age of air travel or even steamships. Back in the days of wooden sailing ships, when the Europeans were busy carting off the riches of the "New World" to their side of the pond, the empty west-bound ships were stabilized with ballast of rock and dirt. Among the living things that were inadvertently scooped up in Europe and dumped over here, the first North American sowbugs obviously went forth and multiplied.

They're not a problem. They keep to themselves. Shrews find them tasty. Kids like to play with them. All in all pretty good immigrants.

Upcoming Events:

• Arbour Day: Saturday May 10th, between 9 a.m. and noon. The Whistler Naturalists will be planting in the Emerald Forest as part of the ongoing restoration of the north gravel pit. The Resort Municipality is supplying the trees and shrubs. Please bring gloves and, if possible, a shovel.

• Stars: May 10 at Spruce Grove Fieldhouse. Local astronomers John Nemy and Carol Legate kick off the stargazing season, rain or stars. 7-11:30 p.m. with indoor and outdoor activities. Free.

• Weekly Nature Walks. Each Wednesday at 6:30 p.m. May 14 walk meets at Lorimer Road, by the Catholic church.

• Bats: The Good, a wee bit of the Bad, and there are none who are Ugly! Thursday May 22nd at 7:30 p.m. The Whistler Naturalists present Dr. Mark Brigham, from the University of Regina, at MY Place. Admission by donation. Doors open at 7 p.m. Followed by a guided outdoor bat search.

Written by: Jack Souther


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