-5 MAV ti Japanese earthworms: a synopsis of the Megadrile species (Oligochaeta) E. G. Easton British Museum (Natural History), London SW7 5BD Contents Introduction 33 Geographical affinities of the Japanese earthworm fauna 34 Classification and Checklist of Japanese earthworms 35 Taxonomy 36 Moniligastridae 37 Biwadrilidae 39 Lumbricidae 40 Ocnerodrilidae 44 Acanthodrilidae 45 Octochaetidae 46 Megascolecidae 46 References 61 Introduction Earthworms play an important part in the soil ecosystem where they participate in organic matter cycles and improve soil structure. They make nitrogen available for plant growth by feeding on organic material in the soil and voiding casts which have a low C/N ratio; in addition the casts contain fragmented litter which is readily broken down by micro-organisms to produce further nitrogen for plant growth. During ingestion the soil particles are ground down in size while the subsequent casts produce a turnover of the soil. Their burrows improve soil aeration and drainage. Although the activities of earthworms are beneficial to man, the worms may be vectors of protozoan, cestode or nematode parasites of mammals and birds which commonly infest pigs and poultry. Earthworms may be very numerous in suitable habitats. One of the highest populations records was that of 845 individuals per square metre (total live weight 245 gm) from an orchard in Europe (Raw, 1959) and populations of 250 per square metre are frequently encountered in grasslands. Over 70 species of earthworms have been recorded from Japan and represent seven of the seventeen currently recognized families of the 'Megadrilacea'. In view of the importance of the group in soil fertility and their common occurrence, it is surprising that no comprehensive study has been published on the rich earthworm fauna of Japan. This situation has compelled the student needing to identify specimens, laboriously to search for matching descriptions scattered throughout the scientific literature beginning with Michaelsen's monograph (1900). A task made all the more difficult by numerous nomenclative changes which have taken place during the last 80 years. It is intended that the present work should go some way to make good this omission and provide a preliminary guide to the many species which have been reported. The Japanese species of the families Biwadrilidae, Lumbricidae, Ocnerodrilidae, Acanthodrilidae and Octochaetidae have been studied extensively but not so the species of the genus Drawida (family Moniligastridae) and of the Pheretima group of genera (Amynthas, Metaphire, Pheretima, Pithemera and Poly-Bull. Br. Mus. nal. Hist. (Zool.) 40 (2) : 33-65 Issued 30 April 1 980
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