Earthworms and Their Allies

by Frank E. Beddard

Thus we may fairly say that the genera Anteoides, Opisthodrilus, Andiodrilus, Holoscolex, Glossoscolex, Rhinodrilus, Andiorrhinus, Fimoscolex, Enantiodrilus, Notiodrilus, Chilota, Yagansia and Kerria are at least very distinctive of S. America and that they are represented by the large majority of species found in that continent, the total being 120 or slightly more.

Leaving the American Continent and adjacent islands and archipelagos, the next great land-mass to receive attention will be the Continent of Africa. In giving a census of the species and genera of earthworms which inhabit this quarter of the globe it must be premised that the facts relate only to Africa south of the Sahara. But little is known of the genera which occur in Algeria and Morocco, but from what little is known it is clear that they should come into consideration in connection with the fauna of Europe and not with that of tropical and south temperate Africa.

We have in the first place to consider an entirely peculiar family, of fair extent in genera and species, which is limited to this region of the world; that is to say with one apparent exception which is clearly only apparent. The genus Eudrilus is one of the few kinds of worms that turns up in collections from every tropical part of the world and even at times from more temperate countries. It is one of those 'peregrine' forms, as Dr Michaelsen has termed them, which possess unusual facilities for extending their range. Presumably its real home is Africa. This family is known as the Eudrilidae though by some it is only regarded as a sub-family of the Megascolecidae. In this family we have the following genera: Eudriloides with 11 species, Platydrilus with 11 species, Megachaetina with two species, Reithrodrilus with one, Stuhlmannia with five species, Notykus and Bogertia with one species each, Metadrilus also with but one species, Pareudrilus with perhaps five, Libyodrilus with one and Nemertodrilus with two species, Metschaina with two species, Eudrilus with two (or possibly more?) species, Parascolex with four species, Preussiella with two, Buttneriodrilus with two, Eminoscolex with 16 species, Hyperiodrilus, Heliodrilus, Alvania, Rosadrilus, Kaffania, Euscolex, Metascolex, Beddardiella, Gardullaria with only one species to each genus, Bettonia with three species, Teleudrilus with 15 species, Polytoreutus with 22 species, Iridodrilus with two, Malodrilus also with two, Neumanniella with eight, Eupolytoreutus with two and Teleutoreutus with only one species.

This completes the list of the Eudrilidae. We will take the huge family Megascolecidae next; and we find in tropical Africa that the genus Dichogaster alone contains at least 93 species confined to Africa, as well as a few which it shares in common with America, and the common and widely spread D. bolavi which has even made its way to Europe. Of the sub-family Ocnerodrilinae we have the genus Gordiodrilus with seven species, a genus which also occurs in Madagascar and the West Indies: Nannodrilus with three species, Diaphorodrilus with one species and a few examples of Ocnerodrilus and its sub-genera, some of which are also forms that occur elsewhere in the world, for example Nematogenia panamensis. Of Pygmæodrilus there are eight or nine species.

Of the sub-family Acanthodrilinae the Cape region of South Africa harbours some seven species of the genus Notiodrilus, of which one however is a West African form. The allied Chilota has 13 species, and there is a peculiar genus Holoscolex near to Yagansia with one species. We next have to deal with the Geoscolecidae, of which a sub-family, Microchaetinae, is mainly found in Africa, the rest being found in the neighbouring Madagascar and some few in the East. Microchaetus contains about 14 species, Tritogenia perhaps three, Callidrilus two, and the genus Glyphidrilus, mainly found in Asia, has one species in the region now under consideration. In addition to these Geoscolecids there is the peculiar and largely aquatic Alma with six or seven species in East, West, and Central, Africa, and in the Nile region.

Summing up the genera which are found in tropical and South Africa we find that there are 44 which are abundant in, or entirely confined to, the region. In addition to these four or so occur in Africa but are either more abundant elsewhere or (as in the case of Chilota and Notiodrilus) are equally distinctive of other parts of the world. The number of species may be estimated at 270, possibly rather more. Clearly therefore this part of the world is much richer than South America, both in numbers of genera actually found, and peculiar to the country, and numbers of species.

Passing from Africa the next definite quarter of the globe which will detain us here is the island of Madagascar, so remarkable for the Mammalian fauna which characterises it, for its lemurs, peculiar Insectivora and Carnivora, and above all by reason of the absence of the prevalent African types such as antelopes, zebras, rhinoceros etc. It is probable that a good deal still remains for discovery among the earthworms of this island; but a considerable number are already known and they are as follows:

The Eudrilidae are completely absent, a state of affairs which is paralleled by the absence of antelopes among mammals.

The sub-family Acanthodrilinae of the family Megascolecidae are represented by four species of the genus Notiodrilus, with which perhaps Maheina braueri from the Seychelles should be included as it presents small differences from Notiodrilus.

Among the Megascolecinae a good many species of Pheretima have been collected both on Madagascar and on certain adjacent islands; but these, with one possible exception, are forms which occur elsewhere and are often indeed very widely distributed 'peregrines,' so that it is hardly permissible to place them among the real inhabitants of Madagascar. The same arguments hold in the case of Lampito mauritii and the ubiquitous Eudrilus and Pontoscolex. But there is the peculiar Howascolex.