The vital question, as to the cause of the permanent increase in field rat populations throughout most tropical and subtropical areas, has been the subject of researchers and fieldmen during the past years, in the hope of finding an answer to this problem. Man has made his way through history wherein he was gradually able to renounce nature and establish his own man-made cultural frame. Unlike other mammals, man has no natural instincts to guide him through life. Brain and spirit have to compensate for lack of physical capabilities and instincts. Man was forced to change his natural surroundings in order to serve his special and ever-growing needs. Survival meant not only using nature but more so changing it in order to develop his culture. The field rat has become man's "cultural treader"! Myomorpha is the largest suborder of the Order Rodentia. Of the 1700 rodents known to man, more than 1100 belong to this group. The greater part of the Myomorpha species are found within two families, which are Cricetidae with about 567 species and Muridae with about 475 species. Most of these rodents live either in trees or under the ground. They rarely collide with man's interest. Only a few rodent species have become "field rats" and seem to dwell in and utilize man's cultural steppe. Some species have even become cosmopolitan and are found in Europe. Asia, Australia, Africa, South, Middle, and North America. leaving only Madagascar and New Zealand without infestation. Field rats are considered the most successful mammals including man. This is due to their fine balance of curiosity and caution, to their instructive behavior and to their well-balanced, often highly developed social structure. The field rat finds, in the man-made or man-modified environment. an almost ideal habitat. Subsistence farming, when looked upon from an ecological viewpoint, has little impact in harming the natural environment. Nature's equilibrium is maintained with this method. Field rats have but a meek chance to dwell within the frame of the traditional farming system.