Earth Worms
Family: Lumbricidae
Genus: Lumbricus
Species: Lumbricus terrestris or Lumricus rubella
Some of this examples from other families are:
1. The rosy-tipped worm, Aporrectodea rosea, is awidespread and can be found in the topsoil in most habitats. The typical size of an adult is 5cm.
2. The compost worm, Eisenia veneta, is usually found in garden compost but can also occur in wet, decaying leaf litter, organic-rich soil and manure heaps. It eats rotting vegetables.
3. The little tree worm, Satchellius mammalis, is widespread in many habitats, from woodlands and field margins to marshy habitats and river banks, but seldom abundant. It lives in leaf litter.
I believe that earthworms were brought onto Saipan from he Europeans when Ferdinand Magellan came to Saipan looking for Spice Island, since then Europeans had been coming in and out of Saipan for supplies and people.
I honestly can't find any information about where it came from, but for all I know that Europeans are the ones that basically brought the earthworms in every places.
REFERENCES:
http://chowhound.chow.com/topics/897947
http://www.nhm.ac.uk/nature-online/life/other-invertebrates/earthworm-slideshow/index.html?utm_source=youtube-earthworms-short-url&utm_medium=youtube-earthworms-short-url&utm_campaign=youtube-earthworms-short-url
http://www.fcps.edu/islandcreekes/ecology/earthworm.htm
http://www.dnr.state.mn.us/invasives/terrestrialanimals/earthworms/index.html
This is a green worm, has a wide distribution and is often the most numerous earthworm in all, but the most acid habitat.
The first earthworms probably arrived with soils and plants brought from Europe. Ships traveling to North America used rocks and soil as ballast which they dumped on shore as they adjusted the ballast weight of the ship. During the late 1800's and early 1900's many European settlers imported European plants that likely had earthworms or earthworm cocoons (egg cases) in their soils. More recently, the widespread use of earthworms as fishing bait has spread them to more remote areas of the state. All common bait worms are non-native species, including those sold as "night crawlers," "Canadian crawlers," "leaf worms," or "angle worms."
That is basically the whole explanation of where earthworms came from.