Art. XII.—Notes on New Zealand Earth-worms.
[Read before the Wellington Philosophical Society, 4th August, 1886.]
The habits of New Zealand earth-worms receive the smallest share of attention from naturalists of any group of our native fauna. This is to be expected, as the study of worms requires much time and patience, and the attractions in a young country among the higher groups is greater, especially one like New Zealand where so many anomalous forms exist, that little time is given to some of the lower orders. Some notes, therefore, on earth-worms, made during eleven years of almost daily experience with them in several localities in the South Island, will contribute a little towards a knowledge of their habits.
As the habits of some of our earth-worms differ considerably from others, I propose to give notes on each species separately, of all I am acquainted with, and the locality where I have collected them. This will enable other workers who may be studying earth-worms in various parts of the country to compare their own observations. This appears to me a sound method of working out perfectly the habits and distribution of all species.
Like other groups of animals, earth-worms vary in their habits, size, and colour, according to the nature of the soil or situation they inhabit; but, so far as I have ascertained, our worms differ, distinctly in some respects, from the British species, so ably treated by Mr. Darwin, in the construction and form of their burrows. I think I will be able to show that New Zealand earth-worms, whether kept in pots in confinement or
in their natural state, differ much in their economy from the British Lumbricus; but more especially in the peculiar semicircular and distinctly branching burrows they construct. This, however, does not apply to all species, as there are others which cannot be said to construct any particular form of burrow: those species, for instance, which live and bore, or burrow, in every direction in loose decaying vegetable matter, or rotten wood, in the bush. The habit of lining their burrows with leaves or other materials is absent with worms in Canterbury and Otago. Mr. A. T. Urquhart, in an excellent paper “On the Habits of Earth-worms in New Zealand,” * has shown that the habit obtains with worms inhabiting the Auckland District. He has also shown that they are content with drawing in leaves to the mouths of their burrows; but he thinks they are chiefly for food. The same habit prevails with worms in Canterbury and Otago; but here in the South, where they live beneath gravel-walks, they draw small stones over to conceal the mouth of the burrows, when not protected by the usual covering of viscid castings. My notes have been gathered in the country between the Rivers Rakaia and Kakanui, and I do not venture to treat of worms beyond the limits of these rivers, although no doubt they will be found to vary little.
Between the two rivers, a distance of 115 miles, worms abound in all the forests, hills, downs, and plains; in some districts they are abundant, in others they occur sparingly. Wherever a clearing is made in the forests they are very active in favourable weather, and throw up immense quantities of castings on the surface. Worms increase in numbers more rapidly in forest clearings than in open pastures; it is due to the mould containing much decayed matter, which they so much relish. They are plentiful beneath dense beds of ferns, or any undergrowth in the forest, and occur sparingly on all the diverging spurs of Mount Peel, Rangitata, up to 4,000 feet. If a prostrate log in the bush be rolled over, large numbers of worms of several species will sometimes be found secreted beneath it; the same may be said of flat stones, and slabs of wood. About farm homesteads, where old bags are left lying on the ground, worms gather beneath them in great numbers, especially during moist or wet weather. They appear to prefer the shelter of rotten bags lying on the surface; it is probably for warmth, as they do not generally burrow beneath them.
In old forests, where small streams flow through them, sections of considerable thickness are often exposed in their banks; at depths varying from 10 to 40 inches a distinct layer
[Footnote] * “Trans. N.Z. Inst.,” vol. xvi., pp. 266–275.
of black mould is visible. These layers appear to have been once the open land inhabited by worms, before the forest spread over it. As the vegetation flourished, the decaying matter from it in the form of leaves, bark, and rotten wood, assisted by the actions of worms, made up in time the superficial mould as we find it to-day in forests. The Canterbury Plains, near the north terrace of the Rangitata River, is covered in some parts with 2 ½ to 4 inches of brown friable mould. It is doubtful whether worms ever existed there in any numbers, as the greater number of various-sized stones lying on the surface exhibit few signs of sinking, and must have remained on the surface for many ages. A few are slightly embedded, while others show a slight impression as if produced by their own weight; the same will be noticed by many on other parts of the Plains, in passing over in the train. These portions of the Plain are exposed to fierce north-west winds, which blow during the spring and early in the summer with terrific force, down the gorges of the Rangitata and Rakaia Rivers, carrying away the finer mould, and depositing it over the Plains along the eastern or lower side.
Worms greatly dislike wind, and, so far as I have ascertained, do not rise to the surface to change quarters, to feed or pair, during dry or cold windy nights, unless accompanied by heavy rains, when they are sometimes flooded out of their burrows. It is during the spring and summer that worms are most active; on mild nights they rise to the surface and pair, and can often be seen lying long after sunrise. I am, therefore, inclined to believe that their absence from those parts of the Plains is chiefly due to their exposure to the dry and fierce “nor'-wester.” On some parts slight depressions occur. After heavy rains small lakes are formed for a time, but generally disappear in a few weeks. The mould in such places is much deeper, and worms more numerous, than on the more stony parts. Although in a few places stones are not seen on the surface, they have sunk through the action of worms, and lie only a few inches below the scanty covering of turf.
Near the banks of the River Hinds, nine miles north of the Rangitata River, where the thick tussock grass breaks—or a few years ago broke—the fury of the wind, worms begin to be more numerous, and along the sea-board for miles inland the land is deep and strong. It is also comparatively free from stones, and worms are abundant. The common Acanthodrilus uliginosus was a few years ago the more numerous. Another larger and undescribed species, of very sluggish habits, is found near the edges of permanent swamps. The other species occurring on the Plains are Endrilus annulatus, E. campestris and E. levis, the first-named of the three being the commones. Beneath the great terrace on the north side of
the Rangitata, there is some excellent land, where worms exist plentifully, and at all seasons, when the weather is favourable, throw up large quantities of castings. The soil, excepting in the swampy parts, is slightly sandy, and probably has been blown on to it from the river-bed by the strong wind. I have no doubt that the great depth of rich mould along the sea-board of Canterbury has been added to considerably by the storms of fine mould blown by the “nor'-westers” from the hills and western portions of the Plains. Some of the stony parts that have been ploughed within the last eight years, and sown down in grass, show signs of worms increasing, by the greater number of castings thrown up annually. When cutting the crops of grain, farmers put little value on the straw, and set the knives of the reapers to clear the stones on the surface. When the grain is threshed out, the straw is sometimes left to rot in large heaps. When trodden down by cattle or sheep, the ground around the mass soon becomes inhabited by Endrilus levis.
Agriculture is favourable to the increase of worms. It is due to the land being loosened by the plough and sweetened by the atmosphere. Worms are the natural fertilizers of the soil, and in favourable weather are constantly replenishing it by the addition of fresh castings. The enormous area of land in New Zealand at present sown down in English grass, will be greatly enriched in a few years for future cropping, through the action of worms. In mild weather, and at all seasons, worms eject more castings on bare patches free from grass, sheep tracks, or well-beaten paths across fields, than on ordinary pasture land, even when many years in grass, but no more than on old lawns that are kept well-mown and rolled. I think this can be explained by the paths and lawns being firm and compact, and having no interstices where they can eject their castings. If burrowing afresh in solid ground, they are compelled to void all the mould they swallow on the surface.
During heavy rains, pools of water are sometimes formed on bare paths; as the weather becomes fine, and the water drains away, a fine sediment or “film of mud” settles on the surface; worms are then very active, and in a few days almost cover the site of the pool with dark mould. As the worms work vigourously, and appear especially to relish the mould, it is probable that many nutritious particles accumulate in the pools, and sink into the earth with the water as it drains away.
Worms throw up castings abundantly in corn-fields, between the stalks of grain, but not for some time after the land settles down; heavy rain settles the ground in a few days. While it remains loose, the worms eject their castings in any crevice. They delight in moist but not wet land, and in dull mild days throw up castings as well as during the night. I first observed this by castings appearing on a tennis lawn through the day,
that had been well rolled in the morning. Some days more are thrown up than others. On those days they are ejecting mould, birds can often be seen flying on to lawns and drawing worms from their burrows.
Some curious sections can be seen on some of the low flats of some Canterbury rivers, notably at the Rakaia, Hakatere, and Tungawai. They consist of thin alternate layers of fine sand and mould. After the deposition of the thin layer of sand, the worms appear to have thrown up a few inches of mould, when another layer of sand was again and again deposited over it. Heavy rains also wash down quantities of fine silt and clay from the clay-banks or “facings” at Albury, and deposit them over the flats below. The worms in a short time throw up abundance of castings; the clay soon becomes perfectly mixed with the mould, and forms land of great depth and good quality.
The cold and wet season of 1884 was specially suited to the actions of earth-worms. Many English grass paddocks adjoining the Haketere or Ashburton River, and broken up eleven years, were daily closely covered with fresh castings. In some parts the whole surface had the appearance of having been covered with a thin covering of dark mould. Many of the castings were of considerable size, and measured in height from ¼ to 1 ½ inches. Owing to the continuous wet weather, it was impossible to collect and weigh them accurately from a measured space, but the amount of mould thrown up must have been considerable, compared to other seasons. On the low undisturbed land, elevated only a few feet above the river, fresh castings were numerous, some portions covered with a fine layer of sand had also a sprinkling of them on the surface.
Worms living in gardens, in cold weather, often cluster together into any piece of rank, loose, or half-decayed manure buried in the soil. Such no doubt is warmer and more pleasant to their bodies; it is also more porous, and allows the wet to percolate through. In rich well—worked gardens, Endrilus annulatus and E. campestris attain their largest size: both species often assume a blackish hue; the former in colour, when inhabiting pastures, is whitish-pink; the latter is generally brownish-red. Both species, with Endrilus levis, are often found between the outer leaves of cabbages and lettuce, and consume much of the softer parts. They cling in great numbers around the stems of blanched celery, and nibble at the more tender parts, often proving very destructive. Although A. uliginosus is found in gardens, they prefer the shelter of large trees in the orchard, or strawberry-beds, to the more cultivated parts, and are not so numerous as the three last-named species, which certainly are the commonest garden worms. They do much injury in flower-pots, and impede the growth of plants by boring or burrowing through the mould,
disturbing and consuming the tender roots, and absorbing all nutritious particles from the soil. If pots are thus infected, and the plants carefully turned out, it will be seen that they keep chiefly to the sides of the pots. The burrow or track against the side is generally open. The tender feeding-roots can be seen “pressed into the walls,” and their actions choked in the viscid lining of the burrow. They deposit their castings among the drainage cracks beneath the mould, and, if not removed, will sometimes effectually choke the drainage. Worms, especially half-grown specimens of Endrilus annulatus, occasionally hibernate in pots, even when the conditions are favourable for their actions.
Some of our worms present some problems, which, as yet, I have not been able to solve. I have already mentioned a large undescribed species existing in a few swampy places on the Plains. Here, near Oamaru, it exists as a more diminutive species, although the conditions appear equally favourable for its development. In one particular swamp, on the south side of the Rangitata Gorge, it attains its maximum size, some specimens measuring 13 and 14 inches, and varies much in colour from each locality, from yellowish-white to dark reddish-pink.
The diseases of earth-worms are little known; yet they are subject to some of a virulent type. I have seen a few individuals of A. uliginosus with hard excrescences on different parts of their bodies. They appear to be painful to the animals, as the slightest touch on one of them causes the worm to shrink. The disease first appears as a small hard pimple, and increases gradually in size. It sometimes almost surrounds the worm's body. At this stage the swelling softens and opens, and the intestines protrude, tinged with blood, when the miserable creature finally rots away.
Mr. Darwin, in his “Vegetable Mould,” page 14, remarks: “After heavy rain succeeding dry weather, an astonishing number of worms may sometimes be seen lying on the surface.” He believed that they were “already sick,” and that their deaths were “merely hastened by the ground being flooded.” He thought if they had been drowned “they would have perished in their burrows.” After many years experience with worms, under all circumstances, I am fully convinced that severe and protracted droughts are both distressing and destructive to them. When drought sets in they are compelled to hibernate, excepting those affecting the edges of permanent swamps. If it be severe, the mould becomes so intensely hard that they are unable to escape, and many perish with exhaustion. If the drought be succeeded by heavy rains, many survive; while some appear to have only sufficient strength to struggle to the surface and die from the same cause, probably accelerated in their weak state by a little cold or exposure. I think this is borne
out by the appearance of their limp and emaciated bodies; but, whatever may be the cause of their deaths, I am of opinion that they die more from the lack of the necessary moisture in the mould they inhabit, than from actual disease.* Mr Urquhart, who has paid some attention to this subject, and who collected worms roaming about after heavy rains, says that they were certainly not all sick, as he obtained healthy as well as sickly and dead worms; but in the case of the healthy ones they were no doubt flooded out of their burrows, and searching for drier ground when picked up. However, that worms are sometimes drowned there is no doubt, as any one can observe after heavy rains. When the water sometimes forms large pools in paddocks, numbers of dead worms are seen lying on the bottom. If it occurs in the spring or summer, the little grey Tern (Sterna antarctica) soon detects them, and small flocks hover and circle about the pools, dipping into the water every few minutes and picking up the dead worms.
Protracted droughts do incalculable injury to the land, not only in destroying worms, but in preventing their actions from replenishing it. The summer and autumn of 1885 and 1886 have been the driest on record, and the most disastrous to earth-worms, that of 1884 the coldest and wettest, but well suited to their actions and the most beneficial to the land.
Mr. Urquhart states that the greatest enemies of worms in the district of Auckland are the Limosa baueri (Var. Redrumped Godwit) and Larmus scopulinus (Mackerel Gull). Here in the South, undoubtedly their strongest enemies, excepting in the more settled districts, are the Weka (Ocydromus australis) and Swamp Hen (Porphyrio melanotus). Both species, being of nocturnal habits, come in for the lion's share. Both the introduced blackbirds and thrushes consume immense numbers. The old adage, “The early bird catches the worm,” is most appropriate when applied to both species. The abundance of worms in settled districts, combined with their habit of lying paired, or roaming about on the surface after daybreak, may be said to be one of the chief causes favouring the great increase of both these English songsters. They, however, do not lose their finer relish for strawberries and other fruits, as they have already gained the same ominous name in this
[Footnote] * Mr. Darwin has fully discussed the effects of an English winter on earth-worms. After observing their movements on the surface, he remarks: “On these occasions, very few dead worms could anywhere be seen,” and continues, “on January 31st, 1881, after a long-continued and unusually severe frost, with much snow, as soon as a thaw set in the walks were marked with innumerable tracks;” but no further mention is made of dead worms
respect as in England.* In the springtime, when lands are ploughed, millions of sea birds, coming inland to breed, follow the plough, and subsist for weeks and months on worms. Several species of birds come a long distance from their nesting-place to follow the plough, and obtain food for their young. When mild weather, with sunshine, succeeds heavy rain, worms often lie in loose mould near the surface. The weka is then very busy, and digs them out with its powerful bill, and consumes great quantities. I have dug up a number of worms, from time to time, minus their tails. I think that during the process of ejecting their castings they are sometimes attacked by birds, which with a quick snap of their beaks tear away a portion of the worm's body. If the tail of a worm be seized with the fingers, when protruding from its burrow, it has great power, and it would be almost impossible to extract it without injury. If only a few segments of the tail are removed, the worms apparently suffer little or no inconvenience, and, if placed in pots, continue active and throw up castings.
The burrows of New Zealand earth-worms form a curious and striking contrast to the British species, described by Mr. Darwin in his valuable work on “Vegetable Mould.” He says, “they run down perpendicularly, or, more commonly, a little obliquely.” He doubted if they branched in solid ground, and adds: “As far as I have seen this does not occur, except in recently-dug ground, and near the surface.” Mr. Urquhart, in his paper already mentioned, states that he “met with instances in which the burrows branched in solid ground, but the branching merely consisted of two short lateral passages at the termination of the burrow, leading into two distinctly separate chambers,” and adds, further, “it is not unusual for two separate burrows to terminate in the same chamber.” Mr. Urquhart, however, does not name the species inhabiting these forms of burrows.
I have already stated that our worms construct semicircular and distinctly-branching burrows. I will select those of A. uliginosus, as it is a common species, and its burrows large. They can be more easily examined than those worked by the smaller forms. In order to examine them perfectly, I have been in the habit of stripping off the turf or covering of
[Footnote] * Probably the best introduced bird is the English starling (Sturnus vulgaris), which is increasing at an unprecedented rate. In settled districts it can be seen in troops of many thousands, busily picking over the ground infested by the larvæ of Odontria striata. Besides consuming great numbers of worms, it bids well at present to exterminate the native Locustina, as they have almost disappeared from districts where the birds are numerous. It would, therefore, be well for collectors to secure abundance of specimens in all districts where the starling is likely to increase.
dead grass with a sharp spade until the mouths were exposed. I then pour a small quantity of a weak saturated solution of corrosive sublimate into the burrow. No sooner does it come in contact with the animal's body than it starts to the surface. Sometimes they rise 12 or 15 inches from the mouth of the burrow where the solution is poured in, but invariably at the mouth to which the worm's head is directed. I never saw one leave its burrow tail first, except when it was a new one in course of making.
Another method of testing the form of these burrows is to insert a fine pliable twig (a weeping-willow answers well) into them, passing it through from one mouth to the other. It is at times difficult to do this, unless the solution be used, as the worms will often refuse to leave the burrow, or when both mouths are close together on the surface, or branches in other directions. When the twig is passed through, it is then easy to dig away the mould or clay on one side and examine the burrow. The two or more mouths vary from 2 to 18 inches apart. When they meet close together on the surface, the worms often lie in the morning with portions of their bodies exposed, with head and tail down each mouth of the burrow, as if enjoying the sun's warmth; but the habit causes the death of many, as the keen eyes of the weka and swamp-hen detect them, and the birds snatch them from their burrows.
When they are working in a considerable depth of rich mould they do not always line their burrows, especially in mild weather. Others, again, are partially lined, being dotted over sparingly with “small globular pellets adhering to the walls.” When living in clay or clayey land the walls of the burrows are thickly lined with viscid earth, and can be examined perfectly, as the dark lining of the burrow contrasts well with the clay. The latter being colder, accounts for the greater thickness of lining. In depth, the burrows vary from 4 to 20 inches; those of the young worms are generally about 3 or 4 inches. It is difficult to dig up whole burrows without fracturing them, yet I have succeeded in raising some perfect ones, which I will forward to the Colonial Museum. When frosts or droughts set in, many of them hibernate for a time; the chambers in which they hibernate are sometimes excavated on one side of the burrow, or a few inches from its walls, but commonly in the middle, and form an enlargement. The chambers are always lined with viscid earth; in addition to this they are often saturated with slime from the animal's body, this forms a cool and slimy bed; they then roll themselves up in the form of a ball, or lie coiled in a circle, with the head in the centre. I have dug them out tied in a perfect knot, or in the form of a running noose, with head and tail placed together. After hibernating for some time, especially in
dry weather, many of them become pale and almost transparent; their bodies also become limp, compared to those that remain active in moister places.
Where two or more worms are found in one burrow, or in separate chambers attached to or leading from it, it can only be explained by some finding their way into them during the night, when roaming about on the surface, and when the mouths of the burrows are open. I have observed that when worms are numerous in solid ground, their burrows often enter or run into each other; they then have the appearance of branching burrows, but the difference can be detected, as a perfect one is either semicircular, or branches gradually like railway points, usually but not always at the bottom, or turn, and rises again to the surface. If worms are about to hibernate, they sometimes descend perpendicularly to a considerable depth, and turn a few inches horizontally before they excavate their chambers; the mould is generally voided in the channel leading from the main burrow, and effectually shuts off the worm from any contact with the cold or dry air.
In some of the branching burrows may often be seen quantities of fresh castings packed tightly into them. The difference between dark mould washed in from the surface, or from the broken walls of a burrow, can be distinguished from castings voided intact, as the latter retain their perfect vermiform shape for a considerable time. There is no doubt whatever that the New Zealand earth-worms “use old burrows for the purpose of voiding their castings in,” as abundance of them can be found in clay, or clayey lands, perfectly packed with them, both fresh and old. The habit of voiding castings, or pairing in their burrows, must tend to the preservation of worms in districts where their enemies are numerous.
During the last summer, undoubtedly the hottest and driest on record in this province, the sun cracked the land which these worms inhabit to a great depth. In order to ascertain the depth they burrowed under the circumstances, we dug several holes, and found them chambered at from 20 to 49 inches from the surface.
Early in September of last year one of the ploughmen informed me that he was ploughing a piece of land on the banks of the Waiareka Creek which contained great numbers of large worms. I went out next day, and followed in the wake of the plough, collecting specimens and examining the burrows. The land was the same peculiar adhesive mould already mentioned, and the worms were numerous and large. Previous to this the weather had been mild, and suited to their actions. The burrows were very perfect, nearly all being of the semicircular form. The air echoed with the delighted cries of gulls, stilts, and terns, all eagerly devouring the large worms.
In regard to the number of worms living in gardens, cultivated fields, and undisturbed Native land, I have made many tests. Worms like naturally rich and even strongly-manured land, but occur plentifully in some districts in poor soils. In an old kitchen-garden on the Rangitata they averaged 7 per square foot; in a similar one at Albury they averaged 8 per square foot; and in another in North Otago, cultivated seventeen years, the average was 7 per square foot. Worms are more numerous in old pastures than in gardens; in some paddocks in the Waiareka Valley they vary from 5 to 16; at Ashburton, on the Plains, paddocks broken up ten years had an average of 8 to each square foot, but they are often found twice more numerous in some parts of the same paddock than in others. In the winter of 1884 we were planting some pines on a piece of Native land, where A. uliginosus was plentiful; at six different places on the slope we dug out a square yard, and counted the worms, which numbered in each as follows: 11, 8, 7, 13, 9, 6; but in some places, lower in the valley, they are more numerous.
The habit of worms rising to the surface and leaving their burrows, caused by beating the soil or other disturbance, is peculiar to two species, Endrilus campestris and E. annulatus. As far as I know, this only occurs on loose ground, particularly in gardens or swampy land that trembles when treading on it. Occasionally, though rarely, they do so in pasture, when the land is soaked after heavy rains; but no manner of beating, or treading, will drive them to the surface in fine weather, either in pastures or on lawns, when they are a few years old, and the ground solid and favourable for their actions. The reverse is the case in loose garden mould: almost any piece not dug for several months, if trod on, or beaten with a spade, will bring some to the surface. This instinct is a subject for speculation; and after experimenting with a view to ascertain the cause, I have no doubt that the sudden breaking or crushing of the burrows causes the worms to extricate themselves and rise to the surface. Both are very sensitive and timid species, and the sense of fear highly developed in both. This considered, I think that any sudden shaking of the mould, or collapse of the burrows, would cause the animals instantly to free themselves, by rising to the surface; but possibly the habit may be acquired from living in loose mould.
I have never lived long enough in one locality to experiment with the sinking of large stones or other bodies, through the actions of worms; but Mr. Urquhart, from experiments made in the Manukau District, has shown that they sink sooner in New Zealand than in England; the gravel on garden walks also sinks much earlier in this country, but the greater number of worms will account for this. There is no doubt that the
accumulation of mould increases more rapidly in our climate than in countries where the winters are long and severe.
The habits of our earth-worms kept in pots differ also from the British species, and are the same highly sensitive animals. If the pots are placed in the open air, they plug the mouths of the burrows with castings, but never plug them or line the burrows with leaves or other materials. They consume fresh or tainted meat; they especially relish the small soft leaves of the common chickweed (Stellaria media). As many as four and five are often drawn into one burrow in a single night. They nibble at almost every variety of mixed fruits or vegetables placed on the pots, and swallow quantities of pounded glass, brick, oyster-shells, and small stones, to aid in the trituration of their food. They are greatly benefited by a change of fresh mould occasionally, and burrow vigorously through it for days after, as if searching for the more nutritious particles it contains. When worms are kept in a limited quantity of mould they become weak and sluggish in their habits. If experiments are tried with worms in penetrating hard compressed soil, or sand, specimens of the same species fresh from the pasture will penetrate it much quicker than those which have been previously kept in confinement. When the mould in pots is pressed down hard, the worms construct the most perfect semicircular and branching burrows, and line them perfectly with viscid castings. The best results are obtained by putting one worm in each pot, according to the size of the animal, but the larger the pot the better, if obtainable.
The following is some account of six species, the other two recorded species (Megalosolex antarctica and M. lineatus,) I have had no experience with:—
Acanthodrilus (?) uliginosus.
Lumbricus uliginosus, Hutton, “Trans. N.Z. Inst.,” vol. ix., p. 351.
Acanthodrilus (?) uliginosus, Hutton, “N.Z. Journ. of Science,” vol. i., p. 586.
Professor Hutton gives this species as 9 inches in length. This is about the average size, although it attains the length of 12 inches. It appears to be distributed over the whole length of the islands, as Mr. Urquhart mentions it occurring in the Auckland District; and I bear from a correspondent that it is plentiful at Riverton, in Southland. In some districts, in suitable soils, it is exceedingly abundant. It attains its greatest size on low-lying, moist flats, or near the margin of sluggish streams, where it is not much disturbed by the plough. It is sparingly found in poor and stony soils, but does not thrive so well as or attain the size of those living where the land is richer and moist. It is a more active species than its larger congener, and during dark damp nights in spring and summer they leave
their burrows in prodigious numbers, and move about on the surface; some are in search of food; some to pair; while others seek new ground to burrow afresh. The nights they appear on the surface, the weka and swamp-hen commit great havoc among them. In some parts of the Waiareka Valley, near Oamaru, the land is intensely adhesive; if ploughed when a little wet, it adheres to the plates of the plough and causes it to stick fast in the furrow. In this particular mould this large species exists in enormous numbers, and attains a great size. From the adhesive nature of the mould, the castings they eject retain their size and form for a long time, and are not so easily defaced or washed away by heavy rains as those thrown up on friable loam. Some thrown up by the larger worms resemble the one figured by Mr. Darwin,* but not so large or perfect. I have not seen an analysis of this mould, but after experimenting with a number of the worms, by handling the animals with the bare hand, and mixing the secretions with the other soils, I am of opinion that its tenacity is chiefly owing to its being saturated with the intestinal secretions of these animals. The same result is obtained by placing a number in a large flower-pot containing friable loam; in a few months it is changed to a rich adhesive mould. The land, however, is well suited for growing wheat, a yield of 70 to 80 bushels per acre being commonly obtained on it. As winter approaches, any castings standing up are soon pulverized by frost, and form small heaps of fine mould on the surface.
Acanthodrilus, sp. nov.
This undescribed species is the largest yet discovered, and although I have stated that it varies in size and colour in different localities, individuals are met with much larger than the largest forms of A. uliginosus. It is found living chiefly in clay, or clayey soils, and its habits are more sluggish than the last-named species. It is limited in its range, being confined to a few places in the districts I have examined. In one spot, a few miles below the Rangitata Gorge, the largest forms are found. Its colour in this locality is reddish-pink. It also occurs in a few places on the Canterbury Plains. At Oamaru I find it in one place, a small swampy patch of Native land; but here it exists as a more diminutive species, and never attains the size of those living in the two other localities. Its burrows are peculiar, as they are more commonly found running horizontally, than perpendicularly or obliquely. They appear to burrow in this manner when inhabiting solid clay. The burrows are of no particular form, but wind in all directions, generally, horizontally, and near the surface, especially if the clay be wet.
[Footnote] * “Vegetable Mould,” p. 129.
When living in deep clayey land, as at the Rangitata Gorge, their burrows have often two distinct mouths, and frequently resemble the letter Y. They work deeper in the mould, usually preferring the clayey subsoil. The dark superficial mould is intermixed with clay, voided in old chambers by the worms. Sometimes the burrows run a few inches horizontally at the bottom. I have never observed this species hibernating, but the habit of living in damp clay may account for it not doing so.
Endrilus (?) levis, Hutton.
Lumbricus levis, Hutton, “Trans. N.Z. Inst.,” vol. ix., p. 351.
Dygaster (?) levis, Hutton, “N.Z. Journ. of Science,” vol. i., p. 586.
This species abounds plentifully in heaps of rotten dung, or any decayed vegetable matter. It attains its greatest size in the bush, among moist beds of dead leaves, or leaf-mould, when its colour is paler and very distinct. It is also found, as Professor Hutton states, “in gardens and fields,” and is “a variable species, sometimes of a greenish hue.” If seized with the fingers, or touched in any way, it secretes a yellow fluid having a fetid odour, which is most distasteful to birds. Caged birds will generally reject it if any other food is obtainable. It is common in Peel Forest, in parts where the mould is deepest and moist. It is somewhat sluggish in habit; and numbers can often be found lying paired beneath slabs of wood, or rotten logs, in which it sometimes bores between the bark and decaying wood, generally on the under surface. It delights most in wet decomposing manure. I have observed it in a matted mass, in the bottom of an open drain leading from a gentleman's kitchen, living in the slimy, soapy pulp. After much wet weather, which causes celery to rot in the trenches, they cling to and nibble at the tender or rotting parts. Where numerous, the rotten celery occasionally partakes of their offensive odour.
Endrilus (?) annulatus, Hutton.
Lumbricus annulatus, Hutton, “Trans. N.Z. Inst.,” vol. ix., p. 352.
This species is the commonest form in all the localities where I have examined; it abounds in gardens and pastures, and is met with in almost every quality of land, from peaty soil on low flats to dry friable loam several thousand feet up the slopes of the ranges; it increases rapidly as the land becomes broken up. It is a very variable species in colour and size, being met with from pale-pink to brownish-black. When living in peaty soil they are pale, and never attain the size of some specimens living in well-manured gardens. When heavy rains fall on newly-dug ground, they often leave their burrows and move about on the surface, leaving a distinct track behind them. This species has the habit of lying closer to the mouth of its
burrow than any other, and is more consumed by birds. It is about 5 to 1 more numerous than any other species. In the summer, during damp mornings, it may be seen moving about on the surface of lawns or pastures, moving its head to and fro, searching for food among the short grass. It has the habit of lying or working close beneath the surface of the mould; this occurs in fine weather after heavy rains, it then falls an easy prey to the weka, which roots them out with its strong bill, and consumes vast numbers. Hundreds can sometimes be seen dead in ditches, or in paddocks where water lodges on the land, after storms of rain.
Endrilus (?) campestris, Hutton.
Lumbricus campestris, Hutton, “Trans. N.Z. Inst.,” vol. ix., p. 352,
Dygaster (?) campestris, Hutton, “N.Z. Journ. of Science,” vol. i., p. 586.
This species is found plentifully in gardens; more so in old ones cultivated some years, than in gardens recently made. A very variable species: Professor Hutton gives its colour as “reddish or olivaceous-green.” In good garden soil it is sometimes almost black, with the clitellum “reddish-brown” and very distinct; I have collected specimens on poor soil clear red. If held before the light of a lamp at night, it is almost transparent. It is a very sensitive and active form; it prefers medium dry to wet land; in gardens in summer it collects into strawberry-beds or under the shade of trees in the orchard: it appears to have a strong liking for both cos or cabbage lettuce, as I find it often between the inner leaves, nibbling at the tender edges. It delights to live in the rot-heap of kitchen gardens, where the refuse of all vegetables is thrown to form manure; it climbs through the heap in all directions, subsisting on the decaying matter. Common in some districts in the open land.
Megalosolex sylvestris, Hutton, “Trans. N.Z. Inst.” vol. ix., p. 351.
This species is plentiful in some places in Peel Forest, It lives in the rotten centres of prostrate trunks, or in the bark. It appears to prefer the dampest parts of the forest. It occurs in the fine mould which often accumulates around the bottom of the stems of tree-ferns. Colour, “dark red-brown.” The young is generally lighter in colour. If placed on level ground, it has a curious habit of wriggling or twisting itself violently about.
The actions of earth-worms on the Canterbury Plains in former times is of much interest, as a little reflection will show that the accumulation of the mantle of mould now covering them must have proceeded at an exceedingly slow rate. The
enormous mass of shingle and sand which underlies the mould would, after their deposition, on account of their great power of absorbing moisture, naturally retard the action of worms for many ages. I have no doubt that worms, or their seed capsules, were transported across the plains by floods in the great rivers, and some probably lodged in the fine silt or sand often deposited on the edges of the streams, leaving them to effect a footing at many places. Some of the best land in the Colony is found on parts of the Plains. The plantations and fences now planted will in a few years serve to break the wind in the more exposed parts affected by the dry north-west gales, and naturally assist the actions of earth-worms. It is well known that some of the heaviest yields of grain are grown in New Zealand, and no one who has examined a heavy crop of wheat growing in this country could fail to observe the astonishing height and thickness of the stalks. This applies to land broken up and in crop for the first time. Mr. Darwin has said that archæologists in England “ought to be grateful” to earth-worms for the preservation of many antiquities of the Roman period. In New Zealand, naturalists are indebted to them for the preservation of many valuable bones of the moa and other extinct birds, and for ethnological relics, buried beneath their castings.
Although earth-worms are “lowly organized” forms of life, any time given to observing their habits is well spent, and only by patient observation can their fertilizing actions on the land be realized.
Note.—Since the foregoing was written, the great drought of the past season has broken up, and been succeeded by the greatest rainfall recorded in New Zealand in a short space of time, and destructive floods, equalled only by those in the memorable year 1868. To show, however, the disastrous effects of droughts on earth-worms, when followed by heavy rains and floods, I will add a few facts which will tend to strengthen my theory of accounting for the death of large numbers of worms. From the 10th to the 24th of July, rain fell sufficient to moisten the land to the depth of 2 inches, but no worms were observed moving on the surface during this time. At Christchurch, heavy rains fell almost continuously from July 28th to August 11th, and the Canterbury Times of August 13th had the following note on worms:—
“An extraordinary number of worms were observed on August 9th, in the side-channels in Gloucester Street. The little creatures, who had evidently been washed out of the earth at various points, seemed to have called meetings of the homeless poor at various points along the road. Just below the
Public School, there must have been a barrow-load of wrigglers in a heap—a large and excited meeting. Further on, by Latimer Square, there was a more thinly-attended meeting, at which those present seemed to have given it up as a bad job, and decided to take no action.”
At Oamaru, heavy rains fell from 10th August to the 22nd. During the afternoon of the 17th, the rain abated for several hours. Large numbers of weakly and apparently healthy worms were then observed moving in all directions on the surface, while some parts of the fields and public roads were literally strewn with the dead bodies of others; but all were of the three smaller species which inhabit open lands. The intestines of nearly all I examined were quite empty. A few only contained minute quantities of clay, which showed that they had burrowed into the clayey subsoil. At the end of the month many of the lakes and pools formed by the heavy rains had subsided. The bottoms of some were covered thickly with the dead bodies of earth-worms in a putrifying state. The drift weeds clinging to wire fences and gorse hedges through which the floods had passed also contained numbers of dead worms. On the hills and downs where they rose to surface they were instantly swept down the slopes, or scoured out of the earth by the numerous small streams formed by the heavy and incessant rains. The weather during the whole period being exceedingly mild, I think their deaths were not in any way accelerated by cold, although vast numbers of both weakly and healthy worms perished by drowning.
I am not sufficiently versed in the anatomy of earth-worms to discuss the subject fully; but I think that, were a number of them collected under the circumstances I have described, and forwarded to some specialist to report on them, it would doubtless settle the question, and explain the cause of their death. Although severe droughts or excessive moisture may generate disease among some species of worms, I am of opinion that more perish from exhaustion during droughts, or from the effects of it, than any other known cause. At Dunedin and other parts of Otago the rainfall for the month of August varied from 16·12 inches to 19·52 inches, and the destruction of worms during the same period was prodigious. These facts are of great interest in illustrating the effects of extremes in seasons on the actions and mortality of earth-worms.