This key is intended for the use of students, teachers, ecologists, soil scientists, amateur biologists, and others with no detailed knowledge of earthworms, who may find it useful from time to time to identify New Zealand earthworms. A total of 182 species, of 34 genera, are included. Further information on these species is contained in the author's The Earthworm Fauna of New Zealand (Lee, 1959). Geographical coverage comprises the mainland of New Zealand (including North, South and Stewart Islands, with associated off-shore islands, Kermadec Islands, Chatham Islands, Auckland Islands, Campbell Islands, Macquarie Island and Antipodes Islands. Only external characters which can be identified with the naked eye, or with the aid of a 5x or lOx hand lens, have been used in compiling the key. except in the case of nine species of the genus Maoridrilus, which can be distinguished only by differences of internal anatomy.

Habitats of New Zealand Earthworms

Earthworms, as their name implies, are for the most part soil inhabiting animals, though some species are found in habitats other than soil. The habitats from which New Zealand earthworms have been collected may be classified as follows:

It should be noted that there are a number of kinds of small worms, related to earthworms, which are aquatic; these are not included in the key.

Principal Divisions of the New Zealand Earthworm Fauna

Two types of native megascolecid worms are illustrated in Figs. 1 and 2, and a typical lumbricid (Allolobophora caliginosa) is illustrated in Fig. 3.

Some Notes on the Anatomy of New Zealand Earthworms

The anatomical characters described below are those that have been used in the key for the identification of species. Colour can only be relied upon for living specimens, and should be noted first when examining an earthworm. The remainder of the characters listed are more easily observed on dead than on living specimens. Identifications can only be made with certainty on sexually mature specimens, i.e. on specimens which have a clitellum.

Orientation: Earthworms usually move forwards, but they also move backwards, so the identity of front and rear is not always apparent from the direction of movement. At the front or head end, there is the prostomium (this is a small fleshy lobe which projects forward above the mouth; it is described and figured below). Anterior segments are in general much larger than posterior segments; there is also much variation in size from one segment to the next anteriorly, while posterior segments tend to be small and of rather regular size (see Figs. 1-3). The clitellum is usually much closer to the anterior end than to the posterior end.

Size: Within a species, considerable size variation is common, so size is not always a useful character for identifying species. However, taken in association with other characters it is often useful, and it can occasionally be the principal means of distinguishing species which differ greatly in size.

Colour: Colour is often useful in identification. Only the colour of living specimens is reliable as the common preservatives and fixatives rapidly remove most of the colour. Some worms are pigmented and the body wall is opaque, while others are unpigmented and may be white and opaque or the body wall may be quite transparent and the blood vessels, intestine, etc., may be readily visible. Pigmented species are usually darker in colour dorsally than ventrally— they may often be white and unpigmented ventrally, but pigmented dorsally. Unpigmented species which are semi-transparent often have a pale pink colour which is due to haemoglobin in the blood; this colour disappears very rapidly when the animal is preserved.

Segments: Segments are the rings into which the body of an earthworm is divided by grooves (the grooves are intersegmental furrows). Much of the identification of earthworms depends on counting segments accurately and determining the positions of various structures in relation to the segments. The following points should be remembered when counting segments:

All earthworms have a prostomium, which is a fleshy lobe that projects forward over the mouth (see Figs. 4-11 and further description below). The prostomium is not counted as a segment; segment 1 is the segment that surrounds the mouth.

In some species, some or all of the segments are divided into smaller rings by secondary annulations, similar to intersegmental furrows (see Figs. 29, 30 and 41). The secondary annulations are often shallower than the intersegmental furrows, but sometimes there is no obvious difference. The chaetae may then be used as a check on the number of segments; there are no chaetae on segment 1, but from segment 2 back there is a ring of chaetae on each segment (see further description under ‘chaetae ’ below).

In some species intersegmental furrows are entirely lacking on the clitellum (see Figs. 12, 14 and further description under ‘clitellum’ below). The chaetae may then be used as a guide to the segmentation.

(In one species (Pheretima peregrina) there are neither intersegmental furrows nor chaetae on the clitellum.)

Prostomium: The prostomium is a small fleshy lobe which projects forward from segment 1 above the mouth opening. Viewed from above, the prostomium may be sharply marked off from segment 1 or may extend back to some extent across the dorsal aspect of segment 1. The extent to which the prostomium is dovetailed into segment 1 is often a useful feature for identification. Four arrangements of prostomium and segment 1 are illustrated in Figs. 4-11. The names tanylobous, prolobous and epilobous are used to describe the types of prostomium illustrated.

Chaetae: The chaetae (sometimes called setae) are small spines, used by earthworms to move through the soil. They are arranged around the perimeter of the segments. There are none on segment 1, but they are found on every segment posterior to segment 1. Usually they can be seen with the naked eye. but a hand lens is sometimes necessary. There may be page break

Figs. 1, 2. ‘Typical’ native (megascolecid) earthworms. Those two figures illustrate typical features of the most common kinds of New Zealand megascolecids
Fig. 1: Note— Anterior segments larger than posterior segments. Clitellum covering dorsal, lateral and ventro-lateral surfaces of 13-19. Chaetae arranged in four pairs per segment (except segment 1), a ventro-lateral pair and a dorso-lateral pair on each side. Two pairs of prostatic pores, a pair on 17 and a pair on 19, each pore situated on a prominent papilla. The two prostatic pores of each side joined by a longitudinal seminal groove, passing across 18. Male pores one on each side, on 18, in the seminal grooves. Spermathecal pores ventro-lateral, in intersegmental furrows, a pair in each of furrows 7/8 and 8/9. Tubercula pubertatis on 11, 12, 20 and 21; on 11 there are two small tubercula, symmetrically arranged, one each side of the ventral mid-line. On 12, 20 and 21 the tubercula are unpaired and lie across the ventral mid-line.
Fig. 2: Note— Anterior segments larger than posterior segments. Clitellum covering entire surface of 14-16. Chaetae numerous on each segment except the first, closely spaced on ventro-lateral, lateral and dorso-lateral aspects of the segments, with wide ventral and dorsal spaces. One pair of combined male and prostatic pores, on 18, each pore situated on a prominent papilla. Spermathecal pores ventro-lateral, in intersegmental furrows, a pair in each of furrows 5/6, 6/7, 7/8 and 8/9. No tubercula pubertatis.
Fig 3. ‘Typical’ introduced (lumbricid) earthworm
Note— Anterior segments larger than posterior segments. Clitellum covering dorsal and lateral surfaces of 28-34 (i.e. clitellum much further back than in megascolecids). Tubercula pubertatis on clitellum as swollen lateral or ventro-lateral ridges, in this on 31-33. Chaetae arranged in four pairs on each segment except the first, a ventro-lateral pair and a dorso-lateral pair on each side. Male pores on 15 (in some lumbricids they are on 13 or 14), one on each side, ventro-lateral; the pores have thickened lips which may (as in this figure) overlap the intersegmental furrows and extend on to adjacent segments. There are no prostatic pores. Spermathecal pores in lumbricid species are usually dorso-lateral, sometimes absent.

page 17 page 18 8, 10, 12 or more than 12 chaetae per segment. The number of chaetae per segment and their arrangement on the segments are very useful characters for the identification of species. Various arrangements are illustrated in Figs. 17-26.

The chaetae on each side of each segment are designated in order from the most ventral to the most dorsal, by the letters a, b, c, etc., as shown in the figures. In describing the location of pores and other external features used in identification it is convenient to imagine a number of longitudinal lines, passing through corresponding chaetae on adjacent segments (see Figs. 27, 28), and refer the location of the pores or other features to the lines.

Clitellum: The clitellum is a glandular thickening of the body wall, present in sexually mature individuals, except in Maoridrilus nelsoni, M. transalpinus, Octochaetus brucei, Hoplochaetina robusta, Rhododrilus albidus, R. minimus, in which the clitellum has not been observed, and page 19

Figs. 4-11. Various kinds of prostomium
Figs. 4, 5. Tanylobous prostomium
4: Dorsal aspect. Grooves defining limits of prostomium extend back right across segment 1. 5: Lateral aspect. Prostomium overhangs mouth opening.
Figs. 6, 7. Prolobous prostomium
6: Dorsal aspect. The prostomium appears as a small lobe, marked off by a transverse groove from segment 1. 7: Lateral aspect.
Figs. 8-11. Two varieties of epilobous prostomium
Longitudinal grooves defining limits of prostomium extend back on to segment 1, but not to the posterior margin of the segment. The prostomium may be marked off by a transverse groove at the end of the longitudinal grooves (as in Figs. 10, 11) or there may be no transverse groove (as in Figs. 8, 9).
Figs. 12-16. Clitellum. Various arrangements: all diagrams illustrate lateral aspect of body.
Figs. 12, 13: Clitellum completely surrounding segments. In Fig. 12 the intersegmental furrows are entirely obliterated; in Fig. 13 intersegmental furrows are still visibe, but slightly suppressed. Nephridiopores in line with chaeta c in Fig. 12, in line with chaeta d in Fig. 13. Figs. 14, 15: Clitellum developed only on dorsal and lateral aspects of segments. Nephridiopores in line with chaeta d in Fig. 14. Fig. 16: Clitellum developed only as a darker pigmented patch on the body wall; dorsal and lateral only. Nephridiopores in line with chaeta d.
Figs. 17-20. Various arrangements of chaetae; diagrammatic representations of chaetal arrangements as seen in a cross-section of the body
Fig. 17: Eight chaetae per segment, arranged in pairs; this the most common chaetal arrangement. Fig. 18: Eight chaetae per segment, arranged in pairs; the body is more or less square in section and the pairs of chaetae are located on the corners of the square. This arrangement of chaetae is found in a number of species of Maoridrilus and Neodrilus. Fig. 19: Eight chaetae per segment; the chaetae are not in pairs, but are fairly evenly spaced on each side of the body. Fig. 20: Eight chaetae per segment; the chaetae are irregularly spaced.

page 20 page 21

Figs. 21-26. Various arrangements of chaetae; diagrammatic representations of chaetal arrangements as seen in a cross-section of the body.
Fig. 21: Ten chaetae per segment: this arrangement is known only in the two species of Decachaetus. Fig. 22: Twelve chaetae per segment, arranged in pairs.
Fig. 23: Twelve chaetae per segment, fairly evenly spaced on each side of the body. Fig. 24: Twelve chaetae per segment, a ventro-lateral pair and a dorso-lateral group of four closely spaced chaetae on each side of the body; this arrangement is known only in Diporochaeta caswelli. Fig. 25: More than twelve chaetae per segment, fairly evenly spaced on each side of the body.
Fig. 26: More than twelve chaetae per segment, arranged in pairs.
Figs. 27, 28. Diagrams showing the lines of chaetae, to which various pores and structures are referred.
Figs. 29-38. Various arrangements of male and prostatic pores and associated structures in megascolecid earthworms.
Figs. 29, 30: Two pairs of prostatic pores, on IT and 19, in line with chaeta f, each pore on a prominent conical papilla; longitudinal seminal groove joins the two prostatic pores on each side, curving slightly laterally and passing between chaetae f and g on 18. Male pores in seminal grooves on 18, between chaetae f and g. The species illustrated is Hoplochaetina polycystis. Figs. 31, 32: Two pairs of prostatic pores, on 17 and 19. in line with chaeta a, each pore on a prominent rounded papilla; a broad longitudinal ridge joins the two prostatic papillae of each side, curving slightly laterally across 18, and passing between chaetae a and b. Seminal grooves run along the ridges, and male pores-are in these grooves, on 18, between chaetae a and b. The species illustrated is Octochaetus sylvestris. Fig. 33: Two pairs of prostatic pores, on 17 and 19, in line with chaeta a, each pore in the centre of a small pale area, not on a papilla. Seminal grooves running longitudinally across 18, close to chaeta a; male pores in seminal grooves on 18, beside chaeta a. The species illustrated is Maoridrilus gravus. Figs. 34, 35: Two pairs of prostatic pores, on 17 and 19, each pore on an elongate, nipple-shaped papilla, the two papillae of each side overhanging 18. A prominent longitudinal ridge joins the two papillae of each side, curving slightly laterally across 18, and seminal grooves follow the crest of the ridge; male pores are on 18, one on each side, in the seminal grooves. The species illustrated is Deinodrilus kanieriensis; in this species the prostatic papillae are exceptionally elongated. Figs. 36, 37: One pair of prostatic pores, on 17, each pore on a small rounded papilla, slightly medial to line of chaeta b. Short seminal groove runs back down each papilla from the prostatic pore to the anterior edge of 18; male pores on 18, one on each side, close to anterior margin, at end of seminal grooves. The species illustrated is Rhododrilus agathis. Fig. 38: One pair of prostatic pores, on 17, occupying the position of the pairs of chaetae a b; pores not on papillae. Seminal grooves running back to the anterior edge of 18; male pores ac end of seminal grooves. The prostatic pores, seminal grooves and male pores are all located in a median ventral depression extending across 17 and overlapping slightly on to 16 and 18. The species illustrated is Neochaeta forsteri.

page 22 extending over several segments between segments 11 and 21 (in native species) or between segments 22 and 37 (in introduced species). It may cover the entire surface of the segments (as in Figs. 12, 13), in which case it is said to be complete, or it may be developed only on dorsal and lateral aspects of the segments (as in Figs. 14, 15, 16); it may cover over and entirely obliterate the intersegmental furrows (as in Figs. 12, 14) or the furrows may be visible but not so well developed (as in Figs. 13, 15), or it may differ only in colour from the surrounding body surface (as in Fig. 16).

Genital Pores: Earthworms are hermaphrodites (i.e. they have both male and female reproductive organs), but they are not self fertilising. During mating, sperm cells are transferred from the male organs of one worm to the spermathecae of the other worm. The sperm cells are then retained in the spermathecae until the female cells (eggs) are produced, when fertilisation is completed.

The external openings of the male and female organs and spermathecae are paired pores.

In the introduced lumbricid worms the male pores are ventro-lateral, on segment 13 or 15 (in all the most common species they are on 15). Each pore is situated in a slit-like depression; in some species the slit is bordered by white lips, narrow in a few species and wide, overlapping on to the adjacent segments in others (see Fig. 3).

In the native megascolecid worms the arrangement of the male pores is more complicated than in lumbricids. Associated with the male reproductive organs are one or two pairs of prostates, which have ducts that open to the exterior close to the male pores, at the prostatic pores, or open at combined male and prostatic pores. The pores are situated on any one, two or three of the segments 16, 17, 18, 19. Fig. 1 shows a megascolecid with male pores opening to the exterior on 18 and prostatic pores opening to the exterior on papillae on 17 and 19. Fig. 2 shows a megascolecid with combined male and prostatic pores on 18. The male and prostatic pores may be on papillae, on longitudinal ridges or transverse ridges, each in a small depression or one on each side of a mid-ventral depression, or they may simply open at the surface without any obvious papillae or depression. Where there are separate male and prostatic pores they are usually connected by longitudinal seminal grooves, one one each side of the body. Various arrangements of the male and prostatic pores and seminal grooves are illustrated in Figs. 29-42.

The spermathecae open to the exterior at paired spermathecal pores. There may be from one to five pairs of spermathecal pores, or, (in Bimastus tenuis and Bimastus eiseni only) there may be no spermathecal pores.

In the introduced lumbricids there are two or three pairs of spermathecal pores, a pair in each of the intersegmental furrows 9/10 and 10/11 (usually) or 8/9, 9/10 and 10/11 (in Allolobophora chlorotica only) or 9/10, 10/11 and 11/12 (in Dendrobaena rubida only), or there may be none (in Bimastus eiseni and Bimastus tenuis). The spermathecal pores are located page 23 in the intersegmental furrows in line with chatea c or chaeta d (i.e. they are lateral or dorso-lateral).

In the native megascolecids there may be one to five pairs of spermathecal pores, in one or more of the intersegmental furrows 4/5, 5/6, 6/7, 7/8 and 8/9, or on the anterior or posterior margins of one or more of the segments 4-9, or occasionally between chaetae a and b on each side of one or more of these segments. Various arrangements of spermathecal pores are illustrated in Figs. 43-46.

Tubercula pubertatis: Tubercula pubertatis are raised, white, glandular pads, ventral or ventro-lateral, and are associated with the genital pores and the clitellum. They are found on segments bearing genital pores or on segments adjacent to those bearing genital pores, or on clitellar segments.

In lumbricids they are ventro-lateral raised pads, symmetrically located on the clitellum (see Fig. 3).

In megascolecids they are more variable in form; they may extend across the ventral mid-line as transverse ridges (as on segments 12, 20 and 21 in Fig.1) or they may be small, paired pads (as on segment 11 in Fig. 1), symmetrically disposed about the ventral mid-line (occasionally they may be asymmetric). They may be on the clitellar segments or on segments bearing genital pores, or on segments adjacent to those bearing genital pores. Not all species have tubercula pubertatis.

The number and disposition of these organs are reliable characters for the identification of lumbricids, but they are rather variable in megascolecids, and although they are often useful in identification, they are not generally used as a sole criterion for the distinction of species.

Nephidiopores: The excretory organs of earthworms are nephridia. Nephridia are of two main types— meganephridia and micronephridia. Meganephridia are paired organs, a pair in every segment except the first, opening to the exterior at nephridiopores. The nephridiopores are placed on each side of each segment, close to the anterior margin of the segment. Micronephridia have no external pores.

The position of the nephridiopores in species with meganephridia is a useful character for identification. They are sometimes easily seen with the naked eye, but frequently a hand lens must be used. They may be ventro-lateral, lateral or dorso-lateral, and their position is always referred to the lines of chaetae. In most earthworms they are in a regular line on each side of the body, as in Fig. 47, where they are in line with chatea c, but in some species they alternate between ventro-lateral and lateral or dorso-lateral positions in successive segments, as in Fig. 48, where they are alternately in line with chaeta b and chaeta c.

Internal Anatomy ofMaoridrilus: The features of internal anatomy necessary for the identification of the nine species of Maoridrilus referred to above are illustrated in Figs. 49 and 50.

To dissect an earthworm, proceed as follows:

How to Use This Key

Earthworms are not easy animals to identify. The key has been made as simple as possible, but some practice will be necessary before it can be used quickly and species can be identified with certainty.

Commence at number 1. Three alternative sets of anatomical features are listed under 1. At the end of each alternative is another number. page 25

Figs 39-42. Various arrangements of male and prostatic pores and associated structures in megascolecid earthworms.
Fig. 39: Prostatic pores on 19, in position of chaeta b on small rounded papillae. Seminal groove runs forward from each prostatic pore to the male pore which is on a small flattish papilla, near the posterior margin of 18. The species illustrated is Sylvodrilus gravus; this is the only New Zealand species with prostatic pores only on 19. Fig. 40: One pair of combined male and prostatic pores, on 18, one on each side of a narrow median ventral depression which extends from the anterior edge of 17 to the posterior edge of 19. The species illustrated is Megascolex animae. Fig. 41: One pair of combined male and prostatic pores, on 18. one on each side of a small median ventral depression; each pore situated on a small round papilla, about in line with chaeta a. The species illustrated is Spenceriella pallida. Fig. 42: One pair of combined male and prostatic pores, on 18, one at each end of a prominent, transverse, ‘dumbbell’-shaped ridge, the pores in line with chaeta b. A number of small tubercula pubertatis surround the ridge bearing the pores. The species illustrated is Diporochaeta obtusa.
Figs. 43-46. Various arrangements of spermathecal pores.
Fig. 43: Pores in intersegmental furrows. Fig. 44: Pores at anterior margins of segments. Fig. 45: Pores at posterior margins of segments. Fig. 46: Pores between chaeta a and b.
Figs. 47, 48. Arrangements of nephridiopores.
Fig. 47: In a single series along the side of the body (in this case, lateral, in line with chaeta c). Fig. 48: Alternating between lateral and ventro-lateral positions in successive segments.

Having decided which of the alternatives under 1 suits your specimen, turn to the number indicated at the end of the alternative, e.g., if the specimen has characters which fit the first alternative, turn to number 2, if it fits the second, turn to number 15, if it fits the third, turn to number 77. Supposing the specimen fits the second alternative, and you have turned to number 15 (on p. 30). under number 15 you will find two further, alternatives, one referring you to number 16 and the other to number 55. Select the alternative which fits your specimen, turn to the number indicated, and further alternatives will be presented. This will be continued for one or more further steps until, by a process of elimination, the species is identified. Sufficient additional detail has been included for each species to check the identification from features which have not been included in the alternatives by which the species was first identified.

Equipment Necessary

For all but nine species the only equipment required for identification is a hand lens (5x or 10x) and considerable patience. Dissection is necessary for the identification of nine species of Maoridrilus. The following equipment is needed for satisfactory dissection of earthworms:

• A dissecting dish— this should have a layer of paraffin wax in the bottom so that the animal can be pinned down.
• Scalpel— preferably with a blade with a sharp point.
• Forceps with fine points.
• Pins.
• A pair of small scissors with sharp points is also useful.

Preservation of Specimens

Specimens may be put straight into 70% ethyl alcohol, and will keep satisfactorily, provided the quantity of earthworms in a container is not so great as to dilute the alcohol below about 50%. Specimens preserved in ethyl alcohol are reasonably easy to dissect, but for class dissection it is worth taking a little more trouble. The worms should first be narcotised4 by putting them in water and adding ethyl alcohol slowly until they cease to react to touch. The narcotised specimens should then be laid out straight (against an edge of a rectangular dish, or a glass plate in a dish) and immersed for 24 hours in a fixative consisting of 70% ethyl alcohol, 40% formalin and glacial acetic acid, mixed in the proportion of 25: 25: 1. Specimens should be stored in 4% formalin and kept straight. page 27

Figs. 49. 50. Some features of the internal anatomy of a ‘typical’ Maoridrilus.
Fig. 49: Dissection from dorsal aspect, segments 1-21. Fig. 50: Lateral view of spermatheca, removed from body.

The Key