Earthworms and the Cluster Fly

Abstract

IN his little book on earthworms and their allies (1912), Beddard expresses the opinion that the northern regions of America possess no indigenous earthworms. This refers to large areas in Canada and the Northern United States. In the mountainous district of Colorado, and the adjacent upland plains, it appears that earthworms were formerly absent. Old settlers assure us that when they first came there were none. This seemed almost incredible, but in recent years Prof. Frank Smith of the University of Illinois has collected earthworms in Colorado, and found only the widespread presumably introduced types. There are indeed a few small native oligochætes in the mountains, but these (Enchytræids) are not pertinent to the present discussion. Beddard infers that the earthworms came from the south, but the Lumbricidæ are evidently of long standing in the Palæarctic region, and as one species (Eisenia nordenskioldi) extends to the Anadyr region in the extreme north-east of Siberia, it is surprising that we find no endemic genera or species in the far north of America. In the more southern parts of North America, apparently including all of the Eastern United States, there is a rather scanty indigenous fauna of Lumbricidæ. These American species are so closely allied to those of the Palæarctic region as to leave no doubt that they are derived from a common source, and we may reasonably assume that their ancestors came by way of Eastern Asia. Thus the present distribution corresponds in a general way with that of certain groups of plants and other organisms which have evidently died out in a large part of North America.