The Zoologist/4th series, vol 1 (1897)/Issue 676/Earthworm Studies (cont.)

by Hilderic Friend

 

EARTHWORM STUDIES.

By the Rev. Hilderic Friend.
Author of 'Flowers and Flower-Lore.'

IV. A Check-List of British Earthworms.

 

Some years ago I drew up a provisional list of the different species of Earthworms which were then known to exist in the British Isles, and published the same in 'The Naturalist' for January, 1893. Since then Rosa's 'Revisione de Lumbricidi,' Beddard's 'Monograph of the Oligochæta,' Ribaucourt's 'Faune Lombricide de la Suisse,' together with a long series of pamphlets and memoranda, have appeared; in addition to my own special reports on the Earthworm fauna of Ireland, England, Normandy, and other parts. It therefore seems desirable that we should summarize our present knowledge for the guidance of collectors at home and students abroad. In this paper I shall place on record all the species and varieties which have come under observation up till the present time, so that we may see in the first place exactly what British species were known to science in this memorable Jubilee year, and at the same time afford a guide to collectors in the identifying of their captures.

In most cases I have, for the sake of convenience, followed Beddard's 'Monograph,' although I cannot in every instance endorse his conclusions. He has absorbed some good species which I have preferred to keep distinct, but in the present state of our knowledge such little differences are inevitable. Although I have given up the specific use of the term Dendrobæna, I believe the day is coming when the large genus Allolobophora will be divided into sections, of which Dendrobæna will be one. Dr. Ribaucourt, indeed, has submitted a synopsis on these lines, which Rosa and others have also from time to time considered and half adopted.

Our indigenous Earthworms fall under three genera, and number at present twenty-three species, besides a few subspecies or well-marked varieties. When I first took up the study some years ago it was assumed that the total number of species did not exceed ten. I believe that two or three other species might be certainly added to the list if the localities as yet unsearched were to be examined. Special attention should be given to the Earthworms of Shetland, the Scottish Highlands, the extreme south-west of England, the Scilly and other isles, of all of which we at present know practically nothing.

Some years ago I adopted the plan of denoting the girdle-segments, and those carrying the glands known as tubercula pubertatis by means of a fraction. Thus 30–36/31–35 would denote that the species had a girdle in the adult which extended from the 30th to the 36th segment, while the 31st to the 35th segments were marked by tubercula. Sometimes, however, the tubercula are on alternate segments, when they are denoted by the symbol 30–36/31:33:35. I have not seen any better method of denoting these important organs, so shall adopt it in the present list. The genus which is still the least satisfactory is Allurus. I formerly reported five species, but to-day I reckon three, with one well-marked variety. No new light having been thrown on Dugès' Amphisbena, I have dropped it from the list. I omit all aliens known to be imported from abroad, such as the ubiquitous Perichæta.

 

I. Genus Lumbricus.

Lip or prostomium cutting right through the peristomium, or forming a complete mortise and tenon. Girdle of five or six segments. On the four innermost a band formed by the tubercula pubertatis on the ventral surface. Eight setæ in each segment but the first, arranged in four couples, not in equidistant rows. Male pores on the 15th segment with or without papillæ. Colour dark brown, red, or violaceous, with iridescence. Body cylindrical in front, flattened behind to enable the creature to retain its hold in the burrow when the head is exposed. Slime exuded especially when irritated, but no coloured fluid thrown out from dorsal pores as is the case with many species of Allolobophora. The species at present known in the British Isles, with some of the localities, are as follows:—

1. Lumbricus herculeus, Savigny. 32–37/33–36. Generally distributed. Records wanted for islands all round the coasts of England, Scotland, and Ireland, and some few counties of England.

2. L. papillosus, Friend. 33–37/34–37. First described by me in Proc. Roy. Irish Ac. (3), ii. p. 453. Hitherto found only in Ireland. A well-marked species, but very similar to, and easily mistaken for, the foregoing.

3. L. festivus, Savigny. 34–39/35–38. Though first described in 1826, it was for nearly sixty years lost to view. I rediscovered it in 1890, and named it L. rubescens. This year it has been found again in France also. It is widely distributed, my own records including Sussex, Kent, Middlesex, Norfolk, Gloucestershire, Yorkshire, Lanarkshire, Down, Dublin, and other counties.

4. L. rubellus, Hoffmeister. 27–32/28–31. Widely distributed. This species is fortunately free from the bewildering array of synonyms attaching to some others.

5. L. castaneus, Savigny. 28–33/29–32. Mr. Beddard remarks truly that this species, like the last, has almost invisible male pores, owing to the absence of a glandular swelling, such as characterizes so many Lumbricidæ. The prostomium has a transverse furrow. It is apparently only to be distinguished from L. rubellus by the different position of the clitellum and the tubercula pubertatis. I should add, "and, as a rule, by the marked difference in their relative sizes, and the tendency of this species to crawl backwards." By an error in the ciphers, Beddard's 'Monograph' makes castaneus four times as long as rubellus (500 mm. to 120), whereas it should be half the length (50 or 60 mm. to 120); the former being ordinarily two or three inches long, and the later (rubellus) about five.

I may here point out an interesting feature in connection with this genus. In 1896 Dr. Ribaucourt described a new Swiss species (L. studeri), specimens of which reached me from Normandy just after the name had been adopted. This species filled up a gap in the chart which he had previously drawn up, and enabled us to set forth the regular succession of segments bearing the clitellum. The plan now stands as follows:—

1	Rubellus	27	28	29	30	31	32
2	Castaneus		28	29	30	31	32	33
3	Melibœus			29	30	31	32	33
[4	Tyrtæus				30	31	32	33	34	35]
5	Studeri					31	32	33	34	35	36	37
6	Herculeus						32	33	34	35	36	37
7	Papillosus							33	34	35	36	37	(38)
8	Festivus								34	35	36	37	38	39

In October, 1893, I remarked ('Naturalist,' p. 296) that L. tyrtæus was probably the same as Allolobophora profuga, and now Dr. Ribaucourt supports my suspicion, though he does not amalgamate the two. The accompanying table or chart gives a bird's-eye view of the British species of the genus which will be helpful to collectors: —

II. Genus Allolobophora.

The members of this genus fall more or less naturally into groups, of which the Dendrobæna is the best defined. As a whole the species of this genus may be known by the lip being only partially dovetailed into the 1st segment. There is a curious exception to this rule in A. eiseni, which has the head arrangement of a true Lumbricus. There is a greater range in the number of girdle-segments than is found in the former genus. While in the British Lumbrici they number six, with the single exception of L. papillosus, in this genus they cover from four to ten segments. The tubercula are also more variable, being (1) absent, (2) on alternate segments, or (3) on a variable number of segments, either as papillæ or in the form of a band on the ventral surface of the clitellum. The male pores are on segment 15, and with or without papillæ. There are eight setæ on each segment, sometimes geminate as in Lumbricus, at other times more or less irregularly disposed. They are usually cylindrical throughout, and frequently exude a turbid fluid which is sometimes very pungent. The colour range is not limited as in Lumbricus. It varies from blue (in A. profuga) to green, ruddy brown, flesh, clay-colour, and alternate bands as in the Brandling. This is by far the largest genus, and has almost a world-wide distribution. The species, subspecies, and varieties known to science now number nearly one hundred. The following are known in the British Isles:—

6. Allolobophora terrestris, Sav.=longa, Ude. 28–35/32–34. Very widely distributed, and often confused with L. herculeus, though easily distinguished therefrom. A pale variety (lactea) often found. The causes of variation have not yet been fully investigated.

7. A. profuga, Rosa. 30–35/31–34. Well-marked species; usually steel-blue, with yellow tail and light-coloured girdle. Found in Ireland, North Wales, and several English counties.

8. A. turgida, Eisen. 28–34/31:33. Widely distributed, and formerly confused with the next, with which also Mr. Beddard wrongly associates it under the name calignosa. I admit that turgida and calignosa are the same, but trapezoides is quite distinct. Ribaucourt has gone carefully into the whole matter.

9. A. trapezoides, Dugès. 27–34/31–33. Note that in one case the papillæ are on two alternate segments (31:33), while in the other they cover three consecutive segments (31—33). There are other differences which at once appear when a good series is under examination. Beddard's remark that Michaelsen found an intermediate form seems to me to suggest the question of hybridity—a subject which I have discussed in 'The Naturalist' (October, 1892).

10. A. rosea, Savigny. 26–32/29–31. Widely distributed. The fluid discharged on irritation leaves a white sediment behind, which seems to be a form of calcium, the study of which might throw some new light on the use of the calciferous glands.

11. A. chlorotica, Savigny. 29–37/31:33:35. Very variable and ubiquitous. I place here for the present the worm I formerly described as A. cambrica. Until we know more of the limits and extent of variation, and can draw a firmer line between species and subspecies, form and variety, it is better not to multiply terms. Several subspecies and varieties have been named by Rosa, Ribaucourt, and others, and our British forms would well repay careful examination.

12. A. georgii, Michaelsen. 29-35/31–33. Tubercula as in trapezoides, which it nearly approaches. I have received it from Clonmore, Co. Clare, Ireland, which is thus far its only decided British habitat.

13. A. fœtida, Savigny. 27–32/28–30. The well-known Brandling of the angler; at once recognized in England by its characteristic colour-bands. On the Continent more than one closely-allied form occurs. The species which comes nearest to it in our British fauna is the next.

14. A. subrubicunda, Eisen. 26–32/28–30. Appears to be generally distributed in the British Isles, and liable to great variation, the forms of which (and their causes) merit special investigation.

15. A. hibernica, Friend. 27–33/30–31. Probably the same as A. veneta, Rosa. At present known from Dublin and Louth in Ireland, but not found in England. (Proc. Royal Irish Acad. 1893, p. 402.)

16. A. mammalis, Savigny. 30–36/33–34. I have found this worm in many parts of the country, and recorded it under Rosa's name A. celtica.

17. A. arborea, Eisen. 27–31/29–30. Should not be placed under subrubicunda, as it is at least a good subspecies. Collected in or received from different parts of England, Ireland, and Wales.

18. A. eiseni, Levinsen. 24–32/0. A pretty anomaly, owing to its having the cephalization of a true Lumbricus—a connecting link between the two genera.

19. A. boeckii, Eisen. 29–33/31–33. Only two authentic records, earlier records belonging to subrubicunda. Apparently a boreal species, but well marked. Much has been written on it by Rosa, Eisen, Ribaucourt, Beddard, and myself. It is found in Yorkshire and Scotland, and should be sought for elsewhere among old decaying timber or fallen trees in parks, woods, and forests.

20. A. constricta, Rosa. 26–31/0. Another of the dendrobænic group. I have found it in Sussex, and this year have received it from the county of Antrim, together with a new variety, the description of which I append.

 

New Variety of Earthworm.

20a. Allolobophora constricta, Rosa, var. geminata, Friend. Length in alcohol, 1¼ in. or 32 mm. First dorsal pore, ⁵⁄₆. Colour like the dendrobænic group generally. Prostomium pale, scarcely at all cutting into the peristomium. Male pore not seated on papillæ; no swelling on segment 16. Girdle extending over seven segments (25—31). No tubercula pubertatis. Total number of segments 60, those behind the girdle triannulate. Setæ geminate or in pairs, as in the Lumbricus type. Found by Dr. Trumbull in wood, Co. Antrim, Ireland, 1897.

 

III. Genus Allurus.

This small group of worms is semi-aquatic, and maybe readily distinguished by the square tail and the position of the male pores on segment 13 instead of 15, as in the two preceding genera. I reckon three British species and one well-marked variety.

21. Allurus tetraedrus, Savigny. 22–26/23–26. Very widely distributed in the British Isles.

21a. A. tetraedrus var. flavus. A beautiful variety found in a stream near Carlisle, and one specimen in Calverley Woods, Yorkshire. Formerly called A.flavus, Friend.

22. A. tetragonurus, Friend. 18–22/19–21. Described by me in 'Science Gossip,' Nov. 1892, p. 243, from a specimen from Bangor, North Wales. Doubtfully referred to Tetragonurus pupa, Eisen. A well-marked worm, but more specimens are desired.

23. A. macrurus, Friend. 15–22/20–21. Found hitherto only in Dublin. The characters of this species are indisputable, but here again more material is wanted.