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:

1.	Terrestrial a. soil, including leaf mould under forest, scrub, etc. b. under logs and stones c. under the bark of dead trees and in rotting logs d. in decaying plant remains in the axils of branches of forest trees.
2.	Aquatic a. in the mud and under stones of stream, pond and lake bottoms b. in the water of deep lakes c. in swamps d. in the intertidal zone on sea shores and in brackish water adjacent to the sea.

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

The earthworms of New Zealand include a large number of species, mainly native, belonging to the family Megascolecidae and a small number of introduced species, belonging to the family Lumbricidae. (See table below.)

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.

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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

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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

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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

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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 of Maoridrilus: 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:

1.	Pin the killed (and preferably fixed) earthworm to the bottom of a dissecting dish, with a pin placed about 10-20 segments back from the – 24 – clitellum, holding the worm down so that the mid-dorsal line is uppermost.
2.	Put sufficient water in the dissecting dish to cover the specimen.
3.	With a scalpel or a sharp-pointed pair of scissors, make an incision through the body wall in the mid-dorsal line, a few segments posterior to the clitellum. When making this incision, try to cut only the body wall, and not allow the scalpel or scissors to penetrate into the intestine.
4.	Carefully extend the cut forward from the first incision, following along the mid-dorsal line to the anterior end of the worm; take care not to cut through the wall of the intestine and other organs in making this cut.
5.	Lay the two sides of the body wall out flat on the dissecting dish and pin them down.

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.

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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.

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The Key

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