The Sub-family Megascolecinae

The sub-family Megascolecinae was established by Michaelsen (1900) as a division of the family Megascolecidae. As defined by Stephenson (1930) it includes all those species of earthworms referable to the family Megascolecidae and having the following characters:

“Chaetae either eight per segment, or numerous, and then either in regular chains or approximated in couples. Clitellum beginning with or in front of xiv. Male pores on xviii. Spermathecal pores, if present, one to seven pairs, in front of the testis segments. Usually one gizzard in front of the testis segments, sometimes two or three, exceptionally none. Mega- or micronephridial. Two pairs of testes and funnels in x and xi, or only one pair. Prostates one pair, tubular or racemose (Pheretima—prostates), each prostatic duct uniting with the vas deferens of the same side and opening in common with it (except in Diplotrema).”

The occurrence of the sub-family Megascolecinae in New Zealand raises some interesting zoogeographical considerations. The “root genus” of the sub-family is taken as Diplotrema, which is found in Queensland and New Caledonia, and from Diplotrema all the other genera have been derived. The genera of the sub-family are now found for the most part in the Indian, Malayan, Oriental and Australasian regions and it is reasonable to assume that any general migration of Megascolecinae into New Zealand must have come from the north. A northern origin for the group is also indicated by its distribution within New Zealand, since nearly all the species are found only in the northern regions of the North Island. The entry of the Megascolecinae into New Zealand would require the postulation of a former land connection of the northern portion of the North Island either directly to Australia or to New Caledonia and the Indo-Malayan islands. Such a land connection need not have been continuous at any one time; it would be sufficient that at times portions of the land connection should have been emergent while other portions remained submerged, and the Megascolecinae were able to progress in stages until they eventually reached New Zealand.

Thirty species, belonging to ten genera of the sub-family, have been identified from the New Zealand region by previous workers and eleven new species, belonging to five of the ten genera, are described in this paper. The following is a list of the ten genera known to occur in the New Zealand region, with notes on their distribution within the region:

None of these genera is peculiar to the New Zealand region. The genera may be identified from the following key:

The relationships of the New Zealand genera are shown in the diagram below, commencing from the “root genus” Diplotrema: