There is a popular belief that a large earthworm species has spread and are living in the walls of rice terraces and are the main factors causing their collapse. Corollary to this is the belief that this earthworm species invaded the rice terraces only recently during the last three decades. Local people in the area speculate that they were introduced just like the golden kuhol and million dollar fish which came in the area also only recently. Since they are perceived as the culprit to the collapse of terrace walls, there is the popular desire among the local people that the said giant earthworm should be exterminated and that this will save the local tourism industry. The present investigators however believe that more scientific investigation should be done to confirm whether or not the allegations against the aforementioned giant earthworms are indeed true. In order to establish the truth, the present study is being conducted. Empirical information from the current study will provide the scientific basis for appropriate informed-decisions to save the Ifugao rice terraces on top of a possibility to help farmers increase their rice production. The Philippines is part of the Indo-Australasian region, home of the earthworm Pheretima-species complex (Sims & Easton, 1972), family Megascolecidae. Particularly, for the Philippines and other islands east of the Wallace’s line, the family Megascolecidae is the only native earthworm family. For any earthworm collected from the field, it is easy to pin down its family by dissecting the worm and carefully note its external and internal morphological characters. With the help of Blakemore’s Introductory Key to the Revised Families of Earthworms of the World (Blakemore, 2006), both external and internal morphological characters of the worm should lead to its correct family. Thus, when an earthworm from the field does not conform to the family Megascolecidae, then there is large probability it belongs to an alien earthworm family. The Philippines claims a record of 71 megascolecid species (Blakemore, 2007) spread among the pheretimoid genera Amynthas (12 species), Archipheretima (4 species), Dendropheretima (2 species), Isarogoscolex (2 species), Metaphire (8 species), Pheretima (12 species), Pheretima (Pheretima) (9 species), Pithemera (2 species), Pleionogaster (16 species) and Polypheretima (4 species). The presence of the tropical Asian megascolecid Perionyx 2longate2, common in dung heap of piggeries and livestock is extant in the Cordillera. A family related to megascolecids, family Octochaetidae, is represented by the genus Dichogaster. Dichogaster nr.curgensis has been reported by Barrion and Litsinger (1997) to infest rice plants in the Cordillera highlands. The family Moniligastridae in the Philippines is credited with 1 genus (Drawida) and 3 species and these could have been unwittingly introduced by man. A certain introduced alien is Pontoscolex corethrurus of the South American family Glossoscolecidae. External and internal morphological descriptions of the aforementioned earthworm species are available in the literature (Baguinon, 1981; Beddard, 1900a, 1912; Blakemore et al., 2007; Easton, 1976; Flores, 2007; Gates,1965; Hong and James, 2004, 2008a, b; James, 2004, 2006; Michaelsen,1900b; Sims and Easton, 1972; Stephenson, 1923). A recent publication by James (2009) describes five new species of Archipheretima thus the number of recorded earthworm species in the Philippines is now pegged at 76.