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Volume 80, 1952
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[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

“Chaetae eight per segment. Spermathecal pores one to five pairs, the last in furrow 7/8 or 8/9 or on segment ix. One gizzard in the region of segments v and vi. Micronephridial at least in the anterior part of the body, often throughout. Prostates tubular, with a simple unbranched canal.” (Stephenson, 1930.)

The species here included in Megascolides have been referred by various authors to Notoscolex, Tokea (a genus which has now been discarded), Megascolides, and in one case (M. morlensem) to Megascolex. The differences between Megascolides and Notoscolex are slight and for diagnostic purposes the form of the prostatic duct is relied upon. A typical Megascolides has simple tubular prostates, each with an unbranched central canal running right through the gland and opening directly to the exterior through the prostatic duct, while a typical Notoscolex has polylobate prostates, each with a diffuse system of ducts ramifying through it and frequently opening into a cavity which is connected with the external pore by the prostatic duct. If all the species of Megascolides and Notoscolex had one or other of these “typical” arrangements of the prostatic ducts, there would be no difficulty in placing a species in its correct genus, but there is a great deal of variation and the two types of prostates grade into one another. It would seem desirable to fuse the two genera, but this would produce a genus

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with a very large number of species, and for convenience it is better that the two genera should be retained.

Benham (1904) established a genus, Tokea, for several species from the North Island of New Zealand which had all the characters of Megascolides, but differed from that genus in one respect. The prostate had a simple central canal, but when sections of the gland were examined, it was found that the gland cells were grouped into small clusters which discharged their secretion into a slight evagination of the central duct. Benham called these small evaginations of the central duct “canalicules”. It was unfortunate that he chose this term, since it really means a small canal and was taken as such by other workers, who placed Benham's species in Notoscolex. However, reference to the figures in Miss Sweet's paper on the structure of prostatic glands (1900), or to Benham's paper (1941) on Megascolides napierensis, in which he figures a cross-section of the prostate of Megascolides (Tokea) esculenta and details of the “canalicules”, will show what Benham meant by the term. I have examined sections of the prostatic gland of other genera of the family Megascolecidae and have found that these “canalicules” are present in the prostates of other genera which have tubular prostates, e.g. in Neodrilus they are present in large numbers. The position of Tokea in relation to Megascolides and Notoscolex has been a subject of much discussion and confusion. Stephenson (1930) summed up the position as it appeared to him, but his statements are in many respects contradictory. He believes that Tokea should go into Notoscolex, a view also adopted by Michaelsen, yet in one part of his monograph (p. 658) he refers to the edibility of certain species of Tokea (Megascolides).” There is one character of Tokea which all the previous workers seem to have overlooked in their discussion. That character is the presence of meganephridia in association with the micronephridia in the posterior segments of the body (see Benham's original description of the genus, 1904). Now, according to the accepted relationships of the genera of the Megascolecinae (as set out above), Megascolides is derived from Plutellus by a change from the meganephridial to the micronephridial condition. In many cases the change is not complete and meganephridia are found in association with micronephridia in the posterior segments of Megascolides. Notoscolex is derived from Megascolides by the branching of the prostatic duct and there are few records of species of Notoscolex with meganephridia and micronephridia co-existent in any of the segments. In view of this fact and the questionable existence of branches in the central prostatic canal of Tokea there can be little doubt that Tokea should be included in Megascolides.

Megascolides mortenseni was referred by Michaelsen (1923) to the genus Megascolex, but reference to the original description shows that it is actually a species of Megascolides. M. reptans and M. unipapillatus were referred by Ude (1905) to Notoscolex, but reference to his descriptions shows that they belong to Megascolides, since they have unbranched tubular prostates.

Twelve species of Megascolides have been recorded from the New Zealand region by previous workers and the following is a list of them.

  • M. napierensis Benham (1941).

  • M. (Tokea) maorica (Benham, 1904).

  • M. (Tokea) decipiens (Benham, 1905).

  • M. (Tokea) kirki (Benham, 1904).

  • M. (Tokea) huttoni (Benham, 1904).

  • M. (Tokea) urewerae (Benham, 1904).

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  • M. (Tokea) suteri (Benham, 1904).

  • M. (Tokea) sapida (Benham, 1904).

  • M. (Tokea) esculenta (Benham, 1904).

  • M. (Notoscolex) reptans (Ude, 1905).

  • M. (Notoscolex) unipapillatus (Ude, 1905).

  • M. (Megascolex) mortenseni (Michaelsen, 1923).

Seven new species, M. viridis, M. ruber, M. parvus, M. raglani, M. fuscus, M. irregularis and M. alba are described in this paper.

The two species M. maorica and M. decipiens are distinguished by the number and position of the tubercula pubertatis. I have found these structures to be extremely variable in number and position and consequently the distinction cannot be upheld. and M. decipiens must be considered synonymous with M. maorica.

Three species, M. huttoni, M. urewerae, and M. suteri, cannot be separated according to the descriptions given by Benham. I have discovered two species which agree fairly closely with Benham's descriptions of M. urewarae and M. suteri, and further notes on the two species are included in this paper. I have not found any species which can be referred to M. huttoni, although M. parvus n.sp., described in this paper, is very similar to M. huttoni. M. napierensis was founded on a single specimen collected from a nurseryman's glasshouse at Napier. I have collected many hundreds of specimens of endemic earthworms from the district surrounding Napier and have not found M. napierensis or any species of any other Megascolecine genus among them. I conclude that M. napierensis is to be regarded as introduced into that one glasshouse in Napier with soil or plants and that it may have come from any part of the world where Megascolides is known. M. mortenseni (Michaelsen) was founded on a single incomplete specimen from Palmerston North. No details of its environment are given, so it cannot be definitely decided whether it is introduced or endemic. It has not been recorded again from Palmerston North or from the surrounding district and it is possible that it was, like M. napierensis, an isolated introduced specimen.

The species of Megascolides known from New Zealand may be identified from the following key:

a1 Two pairs of hearts, in xii and xiii M. napierensis
a2 Three pairs of hearts, in x, xi and xii
b1 Two pairs of spermathecae, in viii and ix
  c1 Calciferous glands absent
    d1 Three pairs of vesiculae seminales, in x, xi and xii M. maorica
    d2 Four pairs of vesiculae seminales, in ix, x, xi and xii M. viridis
  c2 One pair of calciferous glands, in xiv M. kirki
  c1 Two pairs of calciferous glands, in xii and xiii M. ruber
  c4 Five pairs of calciferous glands
    e1 Four pairs of vesiculae seminales, in ix, x, xi and xii M. reptans
    e2 One pair of vesiculae seminales, in xii M. unipapillatus
b2 Three pairs of spermathecae, in vii, viii and ix*
  f1 Two pairs of vesiculae seminales. in ix and xii
    g1 Gizzard in v M. parvus
    g2 Gizzard in vi M. suteri
  f2 Four pairs of vesiculae semmales, in ix, x, xi and xii M. urewerae
a2 Four pairs of hearts

[Footnote] * M. huttoni cannot be definitely separated from any species under this heading, due to inadequacy of description.

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h1 Hearts in ix, x, xi and xii M. raglani
h2 Hearts in x, xi, xii and xiii
  i1 One pair of spermathecae M. fuscus
  i2 Two pairs of spermathecae M. irregularis
  i3 Three pairs of spermathecae
    J1 Spermatheca with elongate tubular sac and slender, pyriform diverticulum M. mortenseni
    J2 Spermatheca with stout ovoidal sac and ovoidal or globular diverticulum
      k1 No oesophageal glands M. sapida
      k2 Oesophageal glands as lateral dilations of the oesophagus in xv M. esculenta
a4 Five pairs of hearts, in ix, x, xi, xii and xiii M. alba

The following are descriptions of the seven new species M. viridis, M. ruber, M. parvus, M. raglani, M. fuscus, M. irregularis and M. alba. Types in my collection.

Megascolides viridis n.sp. (Plate 10, figs. 1–3)

Several specimens of this small species were collected from native forest on a mountainside seven miles west of Motuhora, inland from Gisborne. The most striking character of the species is its colour. Dorsally it is reddish-brown and ventrally it is pale bluish-green. The chaetae arise each from the centre of a small raised white spot. The clitellum does not differ in colour from the remainder of the body, but completely surrounds xiv to xvii, obliterating the intersegmental furrows between those segments.

The specimen on which this description is based is 54 mm. in length and 4.5 mm. in diameter and has 66 segments.

The prostomium is prolobous. There are eight chaetae on each segment, arranged in pairs. On xxiv the arrangement is as follows: ab = 1.5 mm.; cd = 2 mm.; bc = 2 mm.; aa = 2.25 mm., dd = 3 mm.

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There are two pairs of spermathecal pores, a pair at 7/8 and a pair at 8/9, a pore in line with chaeta a of each side in each intersegmental furrow. The female pores are on xiv, a pore on each side anterior and slightly medial to chaeta a. The male pores open to the exterior on xviii, one on each side, slightly lateral to the line joining the chaetae a of the adjacent segments. Each pore is on the apex of a small, rounded, white papilla. There are two small, oval, unpaired, median ventral tubercula pubertatis, one at 13/14, and the other at 18/19. No nephridiopores nor dorsal pores are visible.

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