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EarthwormsLumbricus terrestris
Some scientists estimate that there are approximately 50,000 earthworms per acre of moist soil. Earthworms live in deep, dark, long, and narrow tunnels or burrows under the ground, They cannot tolerate heat and sun and so during the summer they come up to the surface only at night. They also leave their burrows when it rains because it is easier for them to move on the wet surface. After a rain you will notice multitudes of earthworms on the surface. The wet ground allows them to move without drying out.ReproductionAlthough each earthworm is hermaphroditic (having both male and female reproductive systems), it takes two worms to mate and reproduce. The reproductive organs are in the clitellum (the enlarged segments in the middle of an earthworm). The clitellum later forms a cocoon which protects the developing eggs. DietThe brain, hearts, and breathing organs are located in the first few segments of the worm. It has five pairs of hearts! The rest of the inside of an earthworm is filled with the intestines, which digest its food. Earthworms eat soil and the organic material in it - like insect parts and bacteria. The mouth is covered by a flap (called the prostomium) which helps the earthworm sense light and vibrations. Tiny bristles (called setae) are on most segments of the earthworm's body.
Earthworm BurrowsThe tunnels earthworms make beneath the topsoil do a tremendous service to the trees and plants above. Their burrowing aerates the soil, which is why earthworms are called "nature's plough". They not only help bring oxygen down into the soil, but their tunnels allow rainwater carrying organic and inorganic nutrients down deep into the soil where the roots lie. The roots then take up the water and the minerals and recycle them back to the herbaceous plants and woody trees. Life CycleEarthworms are hermaphrodites with both male and female reproductive organs. On warm, moist spring and summer nights, you can often seen hundreds of mating worms coming up out of their burrows. Once they have mated, the girdle like ring around the front of an earthworm, called the clitellum slides along the worm's body, picking up fertilized eggs. When it finally falls off the worm into the soil, it forms a well protected nest or egg case within which the embryo worms develop. PredatorsBecause the body of the earthworm is 70% protein, they are a sought after prey by birds, especially Robins, and by burrowing animals like moles. If you watch a Robin hunting, it pauses, cocks its head, then strikes with its bill, pulling a worm from the ground. The Robin, with its keen eyesight, detects the earthworm's movement in the grass. The earthworm, both sightless and ear-less, can feel the vibrations of the bird on the surface of the ground. HistoryEarthworms were brought to North America by the early European settlers in the 17th and 18th centuries. If earthworms existed in North America prior to this, they were probably wiped out during the last ice age, 10,000 to 50,000 years ago. |
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