I come from a family that celebrated wet weather. When rains were intense, the local grammar school held a "rainy day schedule", which meant an abbreviated day, and I and my siblings would pray that rains would come and linger. Perhaps even more revealing, we would go outside when it rained to splash in the puddles and play in the curbside streams that our hilly suburban streets would form, much to the amazement of our neighbors. For what it's worth, they said the neighborhood was very quiet when we moved away.

Any normal child shares some of this enthusiasm, especially when the rain brings out earthworms. The child in most of us canÕt help but notice the emergence of these sentinels of the dirt, slipping out from their world and undulating onto our sidewalks and streets. A little information about them proves them worthy of following another childhood impulse to not step on them, and perhaps to help them when we can.

There are over 2000 species of earthworms identified. Over 20 are in California, about half of which are native. The most common earthworms here now are exotic. These arrived from Europe with colonists and their plants and soil. A New England settler described the arrival of these earthworms in her area as devastating, that the wells and springs became polluted by the number of dead worms in them. When robins arrived and began to eat them, the exotic earthworms were limited again.

Worms are hermaphroditic, that is, they have both male and female organs. A parent worm will both fertilize another worm's eggs and make its own eggs, which it typically deposits in an "ovate sack" in a soil cavity. Eggs hatch in about 3 to 4 weeks. Hatchlings then mature in about 5 to 6 months, depending on temperature and soil moisture.

Moisture and moderate temperature are essential to earthworm survival. An earthworm is between 65 and 90 percent water, and can easily lose 10 percent of this water in normal activity, enough to immobilize the worm if that water is not replenished. It must have a moist body surface in order to exchange gasses (breathe), and it must have the right amount moisture beside the soil's moisture, the right "hydrostatic pressure", to allow it to burrow into the soil. When it is in the sun or on a dry surface for any length of time, it quickly loses moisture, becomes immobile and will eventually die. Worms can hibernate in the ground to avoid extreme temperatures and drought.

Perhaps no other organism so easily illustrates the web of life for us. Earthworms are "decomposers", one of the many organisms that break down other organisms for food, and in turn, leave behind "waste" material that is eventually food or nutrients for those organisms. As they rise to the surface to eat organic matter, typically decaying plants or manure, different worms use different feeding strategies. All ingest this organic matter, and excrete it in a form that has a remarkable effect on the soil. What they leave behind is considered the gold of any garden--"castings". Earthworm castings contain 5 times the nitrogen, 7 times the available phosphorus, 11 times the potash, and 40 percent more humus than is usually found in the top six inches of topsoil. All these are vital ingredients to the microbes in the soil that help plants grow, and in turn help feed animals that feed on plants. Though blind, earthworms move around a lot, literally eating their way through the earth, and in doing so move great volumes of soil. As many as one half million earthworms move five tons of soil each year and create as many as six million channels per acre, reducing soil compaction and improving soil permeability. As they tunnel they create as much as fifty percent of the air space existing in the top four inches of soil--air space that is once again vital to support plant life.They can move deep into the soil near, though above, the water table, and they can likewise move near to the surface when conditions are right.

Perhaps the most amazing thing about earthworms is that we really don't know much about them. Apparently, we are just learning their basic biological features. We know little about their relationship to soil and to plants. We know less about how they exist in our climate, where there are months of drought each year, and fires are normal events in certain habitats where they are found. I could find no information on how long they typically live in the wild here. It is humbling to know that for all we know, the creatures that drift out into the rainy streets of this season are still unknown, yet vital to the health of so much that is around us.