first stocked with vegetable forms. _When_ it was so stocked (generally
speaking), is equally clear. For as the peculiar coleopterous fauna, of
which an important fragment remains, is mainly composed of species which
are specially attached to certain groups of plants, we may be sure that the
plants were there long before the insects could establish themselves.
However ancient then is the insect fauna the flora must be more ancient
still. It must also be remembered that plants, when once established in a
suitable climate and soil, soon take possession of a country and occupy it
almost to the complete exclusion of later immigrants. The fact of so many
European weeds having overrun New Zealand and temperate North America may
seem opposed to this statement, but it really is not so. For in both these
cases the native vegetation has first been artificially removed by man and
the ground cultivated; and there is no reason to believe that any similar
effect would be produced by the scattering of any amount of foreign seed on
ground already completely clothed with an indigenous vegetation. We might
therefore conclude _a priori_, that the flora of such an island as St.
Helena would be of an excessively ancient type, preserving for us in a
slightly modified form examples of the vegetation of the globe at the time
when the island first rose above the ocean. Let us see then what botanists
tell us of its character and affinities.
The truly indigenous flowering plants are about fifty in number, besides
twenty-six ferns. Forty of the former and ten of the latter are absolutely
peculiar to the island, and, as Sir Joseph Hooker tells us, "with scarcely
an exception, cannot be regarded as very close specific allies of any other
plants at all. Seventeen of them belong to peculiar genera, and of the
others, all differ so markedly as species from their congeners, that not
one comes under the category of being an insular form of a continental
species." The affinities of this flora are, Sir Joseph Hooker thinks, {307}
mainly African and especially South African, as indicated by the presence
of the genera Phylica, Pelargonium, Mesembryanthemum, Oteospermum, and
Wahlenbergia, which are eminently characteristic of southern extra-tropical
Africa. The sixteen ferns which are not peculiar are common either to
Africa, India, or America, a wide range sufficiently explained by the
dust-like spores of ferns, capable of being carried to unknown distances by
the wind, and the great stability of their generic and specific forms, many
of those found in the Miocene deposits of Switzerland, being hardly
distinguishable from living species. This shows, that identity of _species_
of ferns between St. Helena and distant countries does not necessarily
imply a recent origin.
_The Relation of the St. Helena Compositae._--In an elaborate paper on the
Compositae,[71] Mr. Bentham gives us some valuable remarks on the
affinities of the seven endemic species belonging to the genera
Commidendron, Melanodendron, Petrobium, and Pisiadia, which forms so
important a portion of the existing flora of St. Helena. He says: "Although
nearer to Africa than to any other continent, those composite denizens
which bear evidence of the greatest antiquity have their affinities for the
most part in South America, while the colonists of a more recent character
are South African." ... "Commidendron and Melanodendron are among the woody
Asteroid forms exemplified in the Andine Diplostephium, and in the
Australian Olearia. Petrobium is one of three genera, remains of a group
probably of great antiquity, of which the two others are Podanthus in Chile
and Astemma in the Andes. The Pisiadia is an endemic species of a genus
otherwise Mascarene or of Eastern Africa, presenting a geographical
connection analogous to that of the St. Helena Melhaniae,[72] with the
Mascarene Trochetia."
Whenever such remote and singular cases of geographical affinity as the
above are pointed out, the first {308} impression is to imagine some mode
by which a communication between the distant countries implicated might be
effected; and this way of viewing the problem is almost universally
adopted, even by naturalists. But if the principles laid down in this work
and in my _Geographical Distribution of Animals_ are sound, such a course
is very unphilosophical. For, on the theory of evolution, nothing can be
more certain than that groups now broken up and detached were once
continuous, and that fragmentary groups and isolated forms are but the
relics of once widespread types, which have been preserved in a few
localities where the physical conditions were especially favourable, or
where organic competition was less severe. The true explanation of all such
remote geographical affinities is, that they date back to a time when the
ancestral group of which they are the common descendants had a wider or a
different distribution; and they no more imply any closer connection
between the distant countries the allied forms now inhabit, than does the
existence of living Equidae in South Africa and extinct Equidae in the
Pliocene deposits of the Pampas, imply a continent bridging the South
Atlantic to allow of their easy communication.
_Concluding Remarks on St. Helena._--The sketch we have now given of the
chief members of the indigenous fauna and flora of St. Helena shows, that
by means of the knowledge we have obtained of past changes in the physical
history of the earth, and of the various modes by which organisms are
conveyed across the ocean, all the more important facts become readily
intelligible. We have here an island of small size and great antiquity,
very distant from every other land, and probably at no time very much less
distant from surrounding continents, which became stocked by chance
immigrants from other countries at some remote epoch, and which has
preserved many of their more or less modified descendants to the present
time. When first visited by civilised man it was in all probability far
more richly stocked with plants and animals, forming a kind of natural
museum or vivarium in which ancient types, perhaps dating back to the
Miocene {309} period, or even earlier, had been saved from the destruction
which has overtaken their allies on the great continents. Unfortunately
many, we do not know how many, of these forms have been exterminated by the
carelessness and improvidence of its civilised but ignorant rulers; and it
is only by the extreme ruggedness and inaccessibility of its peaks and
crater-ridges that the scanty fragments have escaped by which alone we are
able to obtain a glimpse of this interesting chapter in the life-history of
our earth.
* * * * *
{310}
CHAPTER XV
THE SANDWICH ISLANDS
Position and Physical Features--Zoology of the Sandwich
Islands--Birds--Reptiles--Land-shells--Insects--Vegetation of the
Sandwich Islands--Peculiar Features of the Hawaiian Flora--Antiquity of
the Hawaiian Fauna and Flora--Concluding Observations on the Fauna and
Flora of the Sandwich Islands--General Remarks on Oceanic Islands.
The Sandwich Islands are an extensive group of large islands situated in
the centre of the North Pacific, being 2,350 miles from the nearest part of
the American coast--the bay of San Francisco, and about the same distance
from the Marquesas and the Samoa Islands to the south, and the Aleutian
Islands a little west of north. They are, therefore, wonderfully isolated
in mid-ocean, and are only connected with the other Pacific Islands by
widely scattered coral reefs and atolls, the nearest of which, however, are
six or seven hundred miles distant, and are all nearly destitute of animal
or vegetable life. The group consists of seven large inhabited islands
besides four rocky islets; the largest, Hawaii, being seventy miles across
and having an area 3,800 square miles--being somewhat larger than all the
other islands together. A better conception of this large island will be
formed by comparing it with Devonshire, with which it closely agrees both
in size and shape, though its enormous volcanic mountains rise to nearly
14,000 feet high. {311} Three of the smaller islands are each about the
size of Hertfordshire or Bedfordshire, and the whole group stretches from
north-west to south-east for a distance of about 350 miles. Though so
extensive, the entire archipelago is volcanic, and the largest island is
rendered sterile and comparatively uninhabitable by its three active
volcanoes and their widespread deposits of lava.
[Illustration: MAP OF THE SANDWICH ISLANDS.]
The light tint shows where the sea is less than 1,000 fathoms deep.
The figures show the depth in fathoms.
The ocean depths by which these islands are separated from the nearest
continents are enormous. North, east, and south, soundings have been
obtained a little over or under three thousand fathoms, and these profound
deeps extend over a large part of the North Pacific. We may {312} be quite
sure, therefore, that the Sandwich Islands have, during their whole
existence, been as completely severed from the great continents as they are
now; but on the west and south there is a possibility of more extensive
islands having existed, serving as stepping-stones to the island groups of
the Mid-Pacific. This is indicated by a few widely-scattered coral islets,
around which extend {313} considerable areas of less depth, varying from
two hundred to a thousand fathoms, and which _may_ therefore indicate the
sites of submerged islands of considerable extent. When we consider that
east of New Zealand and New Caledonia, all the larger and loftier islands
are of volcanic origin, with no trace of any ancient stratified rocks
(except, perhaps, in the Marquesas, where, according to Jules Marcou,
granite and gneiss are said to occur) it seems probable that the
innumerable coral-reefs and atolls, which occur in groups on deeply
submerged banks, mark the sites of bygone volcanic islands, similar to
those which now exist, but which, after becoming extinct, have been lowered
or destroyed by denudation, and finally have altogether disappeared except
where their sites are indicated by the upward-growing coral-reefs. If this
view is correct we should give up all idea of there ever having been a
Pacific continent, but should look upon that vast ocean as having from the
remotest geological epochs been the seat of volcanic forces, which from its
profound depths have gradually built up the islands which now dot its
surface, as well as many others which have sunk beneath its waves. The
number of islands, as well as the total quantity of land-surface, may
sometimes have been greater than it is now, and may thus have facilitated
the transfer of organisms from one group to another, and more rarely even
from the American, Asiatic, or Australian continents. Keeping these various
facts and considerations in view, we may now proceed to examine the fauna
and flora of the Sandwich Islands, and discuss the special phenomena they
present.
[Illustration: MAP OF THE NORTH PACIFIC WITH ITS SUBMERGED BANKS.]
The light tint shows where the sea is less than 1,000 fathoms deep.
The dark tint ,, ,, ,, more than 1,000 fathoms deep.
The figures show the depths in fathoms.
_Zoology of the Sandwich Islands: Birds._--It need hardly be said that
indigenous mammalia are quite unknown in the Sandwich Islands, the most
interesting of the higher animals being the birds, which are tolerably
numerous and highly peculiar. Many aquatic and wading birds which range
over the whole Pacific visit these islands, twenty-five species having been
observed, but even of these six are peculiar--a coot, _Fulica alai_; a
moorhen, _Gallinula galeata_ var _sandvichensis_; a rail with rudimentary
wings, _Pennula millei_; a stilt-plover, _Himantopus knudseni_; and {314}
two ducks, _Anas Wyvilliana_ and _Bernicla sandvichensis_. The birds of
prey are also great wanderers. Four have been found in the islands--the
short-eared owl, _Otus brachyotus_, which ranges over the greater part of
the globe, but is here said to resemble the variety found in Chile and the
Galapagos; the barn owl, _Strix flammea_, of a variety common in the
Pacific; a peculiar sparrow-hawk, _Accipiter hawaii_; and _Buteo
solitarius_, a buzzard of a peculiar species, and coloured so as to
resemble a hawk of the American subfamily Polyborinae. It is to be noted
that the genus Buteo abounds in America, but is not found in the Pacific;
and this fact, combined with the remarkable colouration, renders it almost
certain that this peculiar species is of American origin.
The Passeres, or true perching birds, are especially interesting, being all
of peculiar species, and, all but one, belonging to peculiar genera. Their
numbers have been greatly increased since the first edition of this work
appeared, partly by the exertions of American naturalists, and very largely
by the researches of Mr. Scott B. Wilson, who visited the Sandwich Islands
for the purpose of investigating their ornithology, and collected
assiduously in the various islands of the group for a year and a half. This
gentleman is now publishing a finely illustrated work on Hawaiian birds,
and he has kindly furnished me with the following list.
PASSERES OF THE SANDWICH ISLANDS.
MUSCICAPIDAE (Flycatchers).
1. _Chasiempis ridgwayi_ Hawaii.
2. ,, _sclateri_ Kauai.
3. ,, _dolei_ Kauai.
4. ,, _gayi_ Oahu.
5. ,, _ibidis_ Oahu.
6. _Phaeornis obscura_ Hawaii.
7. ,, _myadestina_ Kauai.
MELIPHAGIDAE (Honeysuckers).
8. _Acrulocercus nobilis_ Hawaii.
9. ,, _braccalus_ Kauai.
10. ,, _apicalis_ (extinct) Oahu or Maui.
11. _Chaetoptila angustipluma_ (extinct) Hawaii.
{315}
DREPANIDIDAE.
12. _Drepanis pacifica_ (extinct) Hawaii.
13. _Vastiaria coccinea_ All the Islands.
14. _Hiniatione vireus_ Hawaii.
15. ,, _dolii_ Maui.
16. ,, _sanguinea_ All the Islands.
17. ,, _montana_ Lanai.
18. ,, _chloris_ Oahu.
19. ,, _maculata_ Oahu.
20. ,, _parva_ Kauai.
21. ,, _stejnegeri_ Kauai.
22. _Oreomyza bairdi_ Kauai.
23. _Hemignathus obscurus_ Hawaii.
24. ,, _olivaceus_ Hawaii.
25. ,, _lichtensteini_ Oahu.
26. ,, _lucidus_ Oahu.
27. ,, _stejnegeri_ Kauai.
28. ,, _hanapepe_ Kauai.
29. _Loxops coccinea_ Hawaii.
30. ,, _flammea_ Molokai.
31. ,, _aurea_ Maui.
32. _Chrysomitridops coeruleorostris_ Kaui.
33. ,, _anna_ (extinct)
FRINGILLIDAE (Finches).
34. _Loxioides bailleni_ Hawaii.
35. _Psittirostra psittacea_ All the Islands.
36. _Chloridops kona_ Hawaii.
CORVIDAE (Crows).
37. _Corvus hawaiiensis_ Hawaii.
Many of the birds recently described are representative forms found in the
several islands of the group.
Taking the above in the order here given, we have, first, two peculiar
genera of true flycatchers, a family confined to the Old World, but
extending over the Pacific as far as the Marquesas Islands. Next we have
two peculiar genera (with four species) of honeysuckers, a family confined
to the Australian region, and also ranging over all the Pacific Islands to
the Marquesas. We now come to the most important group of birds in the
Sandwich Islands, comprising seven or eight peculiar genera, and twenty-two
species which are believed to form a peculiar family allied to the Oriental
flower-peckers (Diceidae), and perhaps remotely to the American greenlets
(Vireonidae), or {316} tanagers (Tanagridae). They possess singularly
varied beaks, some having this organ much thickened like those of finches,
to which family some of them have been supposed to belong. In any case they
form a most peculiar group, and cannot be associated with any other known
birds. The last species, and the only one not belonging to a peculiar
genus, is the Hawaiian crow, belonging to the almost universally
distributed genus Corvus.
On the whole, the affinities of these birds are, as might be expected,
chiefly with Australia and the Pacific Islands; but they exhibit in the
buzzard, one of the owls, and perhaps in some of the Drepanididae, slight
indications of very rare or very remote communication with America. The
amount of speciality is, however, wonderful, far exceeding that of any
other islands; the only approach to it being made by New Zealand and
Madagascar, which have a much more varied bird fauna and a smaller
_proportionate_ number of peculiar genera. The Galapagos, among the true
oceanic islands, while presenting many peculiarities have only four out of
the ten genera of Passeres peculiar. These facts undoubtedly indicate an
immense antiquity for this group of islands, or the vicinity of some very
ancient land (now submerged), from which some portion of their peculiar
fauna might be derived. For further details as to the affinities and
geographical distribution of the genera and species, the reader must
consult Mr. Scott Wilson's work _The Birds of the Sandwich Islands_,
already alluded to.
_Reptiles._--The only other vertebrate animals are two lizards. One of
these is a very widespread species, _Ablepharus poecilopleurus_, ranging
from the Pacific Islands to West Africa. The other is said to form a
peculiar genus of geckoes, but both its locality and affinities appear to
be somewhat doubtful.
_Land-shells._--The only other group of animals which has been carefully
studied, and which presents features of especial interest, are the
land-shells. These are very numerous, about thirty genera, and between
three and four hundred species having been described; and it is remarkable
that this single group contains as many species of {317} land-shells as all
the other Polynesian Islands from the Pelew Islands and Samoa to the
Marquesas. All the species are peculiar, and about three-fourths of the
whole belong to peculiar genera, fourteen of which constitute the subfamily
Achatinellinae, entirely confined to this group of islands and constituting
its most distinguishing feature. Thirteen genera (comprising sixty-four
species) are found also in the other Polynesian Islands, but three genera
of Auriculidae (Plecotrema, Pedipes, and Blauneria) are not found in the
Pacific, but inhabit--the former genus Australia, China, Bourbon, and Cuba,
the two latter the West Indian Islands. Another remarkable peculiarity of
these islands is the small number of Operculata, which are represented by
only one genus and five species, while the other Pacific Islands have
twenty genera and 115 species, or more than half the number of the
Inoperculata. This difference is so remarkable that it is worth stating in
a comparative form:--
Inoperculata. Operculata. Auriculidae.
Sandwich Islands 332 5 9
Rest of Pacific Islands 200 115 16
When we remember that in the West Indian Islands the Operculata abound in a
greater proportion than even in the Pacific Islands generally, we are led
to the conclusion that limestone, which is plentiful in both these areas,
is especially favourable to them, while the purely volcanic rocks are
especially unfavourable. The other peculiarities of the Sandwich Islands,
however, such as the enormous preponderance of the strictly endemic
Achatinellinae, and the presence of genera which occur elsewhere only
beyond the Pacific area in various parts of the great continents,
undoubtedly point to a very remote origin, at a time when the distribution
of many of the groups of mollusca was very different from that which now
prevails.
A very interesting feature of the Sandwich group is the extent to which the
species and even the genera are confined to separate islands. Thus the
genera Carelia and Catinella with eight species are peculiar to the island
of Kaui; Bulimella, Apex, Frickella, and Blauneria, to Oahu; Perdicella to
Maui; and Eburnella to Lanai. {318} The Rev. John T. Gulick, who has made a
special study of the Achatinellinae, informs us that the average range of
the species in this sub-family is five or six miles, while some are
restricted to but one or two square miles, and only very few have the range
of a whole island. Each valley, and often each side of a valley, and
sometimes even every ridge and peak possesses its peculiar species.[73] The
island of Oahu, in which the capital is situated, has furnished about half
the species already known. This is partly due to its being more
forest-clad, but also, no doubt, in part to its being better explored, so
that notwithstanding the exceptional riches of the group, we have no reason
to suppose that there are not many more species to be found in the less
explored islands. Mr. Gulick tells us that the forest region that covers
one of the mountain ranges of Oahu is about forty miles in length, and five
or six miles in width, yet this small territory furnishes about 175 species
of Achatinellidae, represented by 700 or 800 varieties. The most important
peculiar genus, not belonging to the Achatinella group, is Carelia, with
six species and several named varieties, all peculiar to Kaui, the most
westerly of the large islands. This would seem to show that the small
islets stretching westward, and situated on an extensive bank with less
than a thousand fathoms of water over it, may indicate the position of a
large submerged island whence some portion of the Sandwich Island fauna was
derived.
_Insects._--Owing to the researches of the Rev. T. Blackburn we have now a
fair knowledge of the Coleopterous fauna of these islands. Unfortunately
some of the most productive islands in plants--Kaui and Maui--were very
little explored, but during a residence of six years the equally rich Oahu
was well worked, and the general character of the beetle fauna must
therefore be considered to be pretty accurately determined. Out of 428
species collected, many being obviously recent introductions, no {319} less
than 352 species and 99 of the genera appear to be quite peculiar to the
archipelago. Sixty of these species are Carabidae, forty-two are
Staphylinidae, forty are Nitidulidae, twenty are Ptinidae, twenty are
Ciodidae, thirty are Aglycyderidae, forty-five are Curculionidae, and
fourteen are Cerambycidae, the remainder being distributed among twenty-two
other families. Many important families, such as Cicindelidae,
Scaraboeidae, Buprestidae, and the whole of the enormous series of the
Phytophaga are either entirely absent or are only represented by a few
introduced species. In the eight families enumerated above most of the
species belong to peculiar genera which usually contain numerous distinct
species; and we may therefore consider these to represent the descendants
of the most ancient immigrants into the islands.
Two important characteristics of the Coleopterous fauna are, the small size
of the species, and the great scarcity of individuals. Dr. Sharp, who has
described many of them,[74] says they are "mostly small or very minute
insects," and that "there are few--probably it would be correct to say
absolutely none--that would strike an ordinary observer as being
beautiful." Mr. Blackburn says that it was not an uncommon thing for him to
pass a morning on the mountains and to return home with perhaps two or
three specimens, having seen literally nothing else except the few species
that are generally abundant. He states that he "has frequently spent an
hour sweeping flower-covered herbage, or beating branches of trees over an
inverted white umbrella without seeing the sign of a beetle of any kind."
To those who have collected in any tropical or even temperate country on or
near a continent, this poverty of insect life must seem almost incredible;
and it affords us a striking proof of how erroneous are those now almost
obsolete views which imputed the abundance, variety, size, and colour of
insects to the warmth and sunlight and luxuriant vegetation of the tropics.
The facts become quite intelligible, however, if we consider that only
{320} minute insects of certain groups could ever reach the islands by
natural means, and that these, already highly specialised for certain
defined modes of life, could only develop slowly into slightly modified
forms of the original types. Some of the groups, however, are considered by
Dr. Sharp to be very ancient generalised forms, especially the peculiar
family Aglycyderidae, which he looks upon as being "absolutely the most
primitive of all the known forms of Coleoptera, it being a synthetic form
linking the isolated Rhynchophagous series of families with the Clavicorn
series. About thirty species are known in the Hawaiian Islands, and they
exhibit much difference _inter se_." A few remarks on each of the more
important of the families will serve to indicate their probable mode and
period of introduction into the islands.
The Carabidae consist chiefly of seven peculiar genera of Anchomenini
comprising fifty-one species, and several endemic species of Bembidiinae.
They are highly peculiar and are all of small size, and may have originally
reached the islands in the crevices of the drift wood from N.W. America
which is still thrown on their shores, or, more rarely, by means of a
similar drift from the N.-Western islands of the Pacific.[75] It is
interesting to note that peculiar species of the same groups of Carabidae
are found in the Azores, Canaries, and St. Helena, indicating that they
possess some special facilities for transmission across wide oceans and for
establishing themselves upon oceanic islands. The Staphylinidae present
many peculiar species of known genera. Being still more minute and usually
more ubiquitous than the Carabidae, there is no difficulty in accounting
for their presence in the islands by the same means of dispersal. The
Nitidulidae, Ptinidae, and Ciodidae being very small and of varied habits,
either the perfect insects, their eggs or larvae, may have been introduced
either by water or wind carriage, or through the agency of birds. The
Curculionidae, being wood bark or nut borers, would have considerable
facilities for transmission by floating timber, fruits, or nuts; and the
eggs or larvae of the {321} peculiar Cerambycidae must have been introduced
by the same means. The absence of so many important and cosmopolitan groups
whose size or constitution render them incapable of being thus transmitted
over the sea, as well as of many which seem equally well adapted as those
which are found in the islands, indicate how rare have been the conditions
for successful immigration; and this is still further emphasized by the
extreme specialisation of the fauna, indicating that there has been no
repeated immigration of the same species which would tend, as in the case
of Bermuda, to preserve the originally introduced forms unchanged by the
effects of repeated intercrossing.
_Vegetation of the Sandwich Islands._--The flora of these islands is in
many respects so peculiar and remarkable, and so well supplements the
information derived from its interesting but scanty fauna, that a brief
account of its more striking features will not be out of place; and we
fortunately have a pretty full knowledge of it, owing to the researches of
the German botanist Dr. W. Hildebrand.[76]
Considering their extreme isolation, their uniform volcanic soil, and the
large proportion of the chief island which consists of barren lava-fields,
the flora of the Sandwich Islands is extremely rich, consisting, so far as
at present known, of 844 species of flowering plants and 155 ferns. This is
considerably richer than the Azores (439 Phanerogams and 39 ferns), which
though less extensive are perhaps better known, or than the Galapagos (332
Phanerogams), which are more strictly comparable, being equally volcanic,
while their somewhat smaller area may perhaps be compensated by their
proximity to the American continent. Even New Zealand with more than twenty
times the area of the Sandwich group, whose soil and climate are much more
varied and whose botany has been thoroughly explored, has not a very much
larger number of flowering plants (935 species), while in ferns it is
barely equal.
{322}
The following list gives the number of indigenous species in each natural
order.
_Number of Species in each Natural Order in the Hawaiian Flora, excluding
the introduced Plants._
DICOTYLEDONS. 48. Gentianaceae (Erythraea) 1
49. Loganiaceae 7
1. Ranunculaceae 2 50. Apocynaceae 4
2. Menispermaceae 4 51. Hydrophyllaceae (Nama ...
3. Papaveraceae 1 allies Andes) 1
4. Cruciferae 3 52. Oleaceae 1
5. Capparidaceae 2 53. Solanaceae 12
6. Violaceae 8 54. Convolvulaceae 14
7. Bixaceae 2 55. Boraginaceae 3
8. Pittosporaceae 10 56. Scrophulariaceae 2
9. Caryophyllaceae 23 57. Gesneriaceae 24
10. Portulaceae 3 58. Myoporaceae 1
11. Guttiferae 1 59. Verbenaceae 1
12. Ternstraemiaceae 1 60. Labiatae 39
13. Malvaceae 14 61. Plantaginaceae 2
14. Sterculiaceae 2 62. Nyctaginaceae 5
15. Tiliaceae 1 63. Amarantaceae 9
16. Geraniaceae 6 64. Phytolaccaceae 1
17. Zygophyllaceae 1 65. Polygonaceae 3
18. Oxalidaceae 1 66. Chenopodiaceae 2
19. Rutaceae 30 67. Lauraceae 2
20. Ilicineae 1 68. Thymelaeaceae 7
21. Celastraceae 1 69. Santalaceae 5
22. Rhamnaceae 7 70. Loranthaceae 1
23. Sapindaceae 6 71. Euphorbiaceae 12
24. Anacardiaceae 1 72. Urticaceae 15
25. Leguminosae 21 73. Piperaceae 20
26. Rosaceae 6
27. Saxifragaceae (trees) 2 MONOCOTYLEDONS.
28. Droseraceae 1
29. Halorageae 1 74. Orchidaceae 3
30. Myrtaceae 6 75. Scitaminaceae 4
31. Lythraceae 1 76. Iridaceae 1
32. Onagraceae 1 77. Taccaceae 1
33. Cucurbitaceae 8 78. Dioscoreaceae 2
34. Ficoideae 1 79. Liliaceae 7
35. Begoniaceae 1 80. Commelinaceae 1
36. Umbelliferae 5 81. Flagellariaceae 1
37. Araliaceae 12 82. Juncaceae 1
38. Rubiaceae 49 83. Palmaceae 3
39. Compositae 70 84. Pandanaceae 2
40. Lobeliaceae 58 85. Araceae 2
41. Goodeniaceae 8 86. Naiadaceae 4
42. Vaccinaceae 2 87. Cyperaceae 47
43. Epacridaceae 2 88. Graminaceae 57
44. Sapotaceae 3
45. Myrsinaceae 5 VASCULAR CRYPTOGAMS.
46. Primulaceae (Lysimachia)
shrubs 6 Ferns 136
47. Plumbaginaceae 1 Lycopodiaceae 17
Rhizocarpeae 2
{323}
_Peculiar Features of the Flora._--This rich insular flora is wonderfully
peculiar, for if we deduct 115 species, which are believed to have been
introduced by man, there remain 705 species of flowering plants of which
574, or more than four-fifths, are quite peculiar to the islands. There are
no less than 38 peculiar genera out of a total of 265 and these 38 genera
comprise 254 species, so that the most isolated forms are those which most
abound and thus give a special character to the flora. Besides these
peculiar types, several genera of wide range are here represented by highly
peculiar species. Such are the Hawaiian species of Lobelia which are woody
shrubs either creeping or six feet high, while a species of one of the
peculiar genera of Lobeliaceae is a tree reaching a height of forty feet.
Shrubby geraniums grow twelve or fifteen feet high, and some vacciniums
grow as epiphytes on the trunks of trees. Violets and plantains also form
tall shrubby plants, and there are many strange arborescent compositae, as
in other oceanic islands.
The affinities of the flora generally are very wide. Although there are
many Polynesian groups, yet Australian, New Zealand, and American forms are
equally represented. Dr. Pickering notes the total absence of a large
number of families found in Southern Polynesia, such as Dilleniceaea,
Anonaceae, Olacaceae, Aurantiaceae, Guttiferae, Malpighiaceae, Meliaceae,
Combretaceae, Rhizophoraceae, Melastomaceae, Passifloraceae, Cunoniaceae,
Jasminaceae, Acanthaceae, Myristicaceae, and Casuaraceae, as well as the
genera Clerodendron, Ficus, and epidendric orchids. Australian affinities
are shown by the genera Exocarpus, Cyathodes, Melicope, Pittosporum, and by
a phyllodinous Acacia. New Zealand is represented by Ascarina, Coprosma,
Acaena, and several Cyperaceae; while America is represented by the genera
Nama, Gunnera, Phyllostegia, Sisyrinchium, and by a red-flowered Rubus and
a yellow-flowered Sanicula allied to Oregon species.
There is no true alpine flora on the higher summits, but several of the
temperate forms extend to a great elevation. Thus Mr. Pickering records
Vaccinium, Ranunculus, Silene, Gnaphalium and Geranium, as occurring above
ten {324} thousand feet elevation; while Viola, Drosera, Acaena, Lobelia,
Edwardsia, Dodonaea, Lycopodium, and many Compositae, range above six
thousand feet. Vaccinium and Silene are very interesting, as they are
almost peculiar to the North Temperate zone; while many plants allied to
Antarctic species are found in the bogs of the high plateaux.
The proportionate abundance of the different families in this interesting
flora is as follows:--
1. Compositae 70 species, 12. Urticaceae 15 species,
2. Lobeliaceae 58 ,, 13. Malvaceae 14 ,,
3. Graminaceae 57 ,, 14. Convolvulaceae 14 ,,
4. Rubiaceae 49 ,, 15. Araliaceae 12 ,,
5. Cyperaceae 47 ,, 16. Solanaceae 12 ,,
6. Labiatae 39 ,, 17. Euphorbiaceae 12 ,,
7. Rutaceae 30 ,, 18. Pittosporaceae 10 ,,
8. Gesneriaceae 24 ,, 19. Amarantaceae 9 ,,
9. Caryophyllaceae 23 ,, 20. Violaceae 8 ,,
10. Leguminosae 21 ,, 21. Goodeniaceae 8 ,,
11. Piperaceae 20 ,,
Nine other orders, Geraniaceae, Rhamnaceae, Rosaceae, Myrtaceae,
Primulaceae, Loganiaceae, Liliaceae, Thymelaceae, and Cucurbitaceae, have
six or seven species each; and among the more important orders which have
less than five species each are Ranunculaceae, Cruciferae, Vaccinacae,
Apocynaceae, Boraginaceae, Scrophulariaceae, Polygonaceae, Orchidaceae, and
Juncaceae. The most remarkable feature here is the great abundance of
Lobeliaceae, a character of the flora which is probably unique; while the
superiority of Labiatae to Leguminosae and the scarcity of Rosaceae and
Orchidaceae are also very unusual. Composites, as in most temperate floras,
stand at the head of the list, and it will be interesting to note the
affinities which they indicate. Omitting eleven species which are
cosmopolitan, and have no doubt entered with civilised man, there remain
nineteen genera and seventy species of Compositae in the islands. Sixty-one
of the species are peculiar, as are eight of the genera; while the genus
Lipochaeta with eleven species is only known elsewhere in the Galapagos,
where a single species occurs. We may therefore consider that nine out of
the nineteen genera of Hawaiian {325} Compositae are really confined to the
Archipelago. The relations of the peculiar genera and species are indicated
in the following table.[77]
_Affinities of Hawaiian Composites._
No. of
Peculiar Genera. Species. External Affinities of the Genus.
Remya 2 Very peculiar. Allied to the North American
genus Grindelia.
Tetramolobium 7 South Temperate America and Australia.
Lipochaeta 11 Allied to American genera.
Campylothaeca 12 With Tropical American species of Bidens and
Coreopsis.
Argyroxiphium 2 With the Mexican Madieae.
Wilkesia 2 Same affinities.
Dubantia 6 With the Mexican Raillardella.
Raillardia 12 Same affinities.
Hesperomannia 2 Allied to Stifftia and Wunderlichia of Brazil.
Peculiar Species.
Lagenophora 1 Australia, New Zealand, Antarctic America,
Fiji Islands.
Senecio 2 Universally distributed.
Artemisia 2 North Temperate Regions.
The great preponderance of American relations in the Compositae, as above
indicated, is very interesting and suggestive, since the Compositae of
Tahiti and the other Pacific Islands are allied to Malaysian types. It is
here that we meet with some of the most isolated and remarkable forms,
implying great antiquity; and when we consider the enormous extent and
world-wide distribution of this order (comprising about ten thousand
species), its distinctness from all others, the great specialisation of its
flowers to attract insects, and of its seeds for dispersal by wind and
other means, we can hardly doubt that its origin dates back to a very
remote epoch. We may therefore look upon the Compositae as representing the
most ancient portion of the existing flora of the Sandwich Islands,
carrying us back to a very remote period when the facilities for
communication with America were greater than they are now. This may be
indicated by the two deep submarine banks in the North Pacific, between the
Sandwich Islands and San Francisco, which, from an ocean floor {326} nearly
3,000 fathoms deep, rise up to within a few hundred fathoms of the surface,
and seem to indicate the subsidence of two islands, each about as large as
Hawaii. The plants of North Temperate affinity may be nearly as old, but
these may have been derived from Northern Asia by way of Japan and the
extensive line of shoals which run north-westward from the Sandwich
Islands, as shown on our map. Those which exhibit Polynesian or Australian
affinities, consisting for the most part of less highly modified species,
usually of the same genera, may have had their origin at a later, though
still somewhat remote period, when large islands, indicated by the
extensive shoals to the south and south-west, offered facilities for the
transmission of plants from the tropical portions of the Pacific Ocean.
It is in the smaller and most woody islands in the westerly portion of the
group, especially in Kauai and Oahu, that the greatest number and variety
of plants are found and the largest proportion of peculiar species and
genera. These are believed to form the oldest portion of the group, the
volcanic activity having ceased and allowed a luxuriant vegetation more
completely to cover the islands, while in the larger and much newer islands
of Hawaii and Maui the surface is more barren and the vegetation
comparatively monotonous. Thus while twelve of the arborescent Lobeliaceae
have been found on Hawaii no less than seventeen occur on the much smaller
Oahu, which has even a genus of these plants confined to it.
It is interesting to note that while the non-peculiar genera of flowering
plants have little more than two species to a genus, the endemic genera
average six and three-quarter species to a genus. These may be considered
to represent the earliest immigrants which became firmly established in the
comparatively unoccupied islands, and have gradually become modified into
such complete harmony with their new conditions that they have developed
into many diverging forms adapting them to different _habitats_. The
following is a list of the peculiar genera with the number of species in
each. {327}
_Peculiar Hawaiian Genera of Flowering Plants._
Genus. No. of Species. Natural Order.
1. Isodendrion 3 Violaceae.
2. Schiedea (seeds rugose or muricate) 17 Caryophyllaceae.
3. Alsinidendron 1 ,,
4. Pelea 20 Rutaceae.
5. Platydesma 4 ,,
6. Mahoe 1 Sapindaceae.
7. Broussaisia 2 Saxifragaceae.
8. Hildebrandia 1 Begoniaceae.
9. Cheirodendron (fleshy fruit) 2 Araliaceae.
10. Pterotropia (succulent) 3 ,,
11. Triplasandra (drupe) 4 ,,
12. Kadua (small, flat, winged seeds) 16 Rubiaceae.
13. Gouldia (berry) 5 ,,
14. Bobea (drupe) 5 ,,
15. Straussia (drupe) 5 ,,
16. Remya 2 Compositae.
17. Tetramolobium 7 ,,
18. Lipochaeta 11 ,,
19. Campylotheca 12 ,,
20. Argyroxiphium 2 ,,
21. Wilkesia 2 ,,
22. Dubautia 6 ,,
23. Raillardia 12 ,,
24. Hesperomannia 2 ,,
25. Brighamia 1 Lobeliaceae.
26. Clermontia (berry) 11 ,,
27. Rollandia 6 ,,
28. Delissea 7 ,,
29. Cyanea 28 ,,
30. Labordea 9 Loganiaceae.
31. Nothocestrum 4 Solanaceae.
32. Haplostachys (nucules dry) 3 Labiatae.
33. Phyllostegia (nucules fleshy) 16 ,,
34. Stenogyne (nucules fleshy) 16 ,,
35. Nototrichium 3 Amarantaceae.
36. Charpentiera 2 ,,
37. Touchardia 1 Urticaceae.
38. Neraudia 2 ,,
----
Total 254 species.
The great preponderance of the two orders Compositae and Lobeliaceae are
what first strike us in this list. In the former case the facilities for
wind-dispersal afforded by the structure of so many of the seeds render it
comparatively easy to account for their having reached the islands at an
early period. The Lobelias, judging from Hildebrand's descriptions, may
have been transported in several {328} different ways. Most of the endemic
genera are berry-bearers and thus offer the means of dispersal by
fruit-eating birds. The endemic species of the genus Lobelia have sometimes
very minute seeds, which might be carried long distances by wind, while
other species, especially Lobelia gaudichaudii, have a "hard, almost woody
capsule which opens late," apparently well adapted for floating long
distances. Afterwards "the calycine covering withers away, leaving a
fenestrate woody network" enclosing the capsule, and the seeds themselves
are "compressed, reniform, or orbicular, and margined," and thus of a form
well adapted to be carried to great heights and distances by gales or
hurricanes.
In the other orders which present several endemic genera indications of the
mode of transit to the islands are afforded us. The Araliaceae are said to
have fleshy fruits or drupes more or less succulent. The Rubiaceae have
usually berries or drupes, while one genus, Kadua, has "small, flat, winged
seeds." The two largest genera of the Labiatae are said to have "fleshy
nucules," which would no doubt be swallowed by birds.[78]
_Antiquity of the Hawaiian Fauna and Flora._--The great antiquity implied
by the peculiarities of the fauna and flora, no less than by the
geographical conditions and surroundings, of this group, will enable us to
account for another peculiarity of its flora--the absence of so many
families found in other Pacific Islands. For the earliest immigrants would
soon occupy much of the surface, and become specially modified in
accordance with the conditions of the locality, and these would serve as a
barrier against the intrusion of many forms which at a later {329} period
spread over Polynesia. The extreme remoteness of the islands, and the
probability that they have always been more isolated than those of the
Central Pacific, would also necessarily result in an imperfect and
fragmentary representation of the flora of surrounding lands.
_Concluding Observations on the Fauna and Flora of the Sandwich
Islands._--The indications thus afforded by a study of the flora seem to
accord well with what we know of the fauna of the islands. Plants having so
much greater facilities for dispersal than animals, and also having greater
specific longevity and greater powers of endurance under adverse
conditions, exhibit in a considerable degree the influence of the primitive
state of the islands and their surroundings; while members of the animal
world, passing across the sea with greater difficulty and subject to
extermination by a variety of adverse conditions, retain much more of the
impress of a recent state of things, with perhaps here and there an
indication of that ancient approach to America so clearly shown in the
Compositae and some other portions of the flora.
GENERAL REMARKS ON OCEANIC ISLANDS.
We have now reviewed the main features presented by the assemblages of
organic forms which characterise the more important and best known of the
Oceanic Islands. They all agree in the total absence of indigenous mammalia
and amphibia, while their reptiles, when they possess any, do not exhibit
indications of extreme isolation and antiquity. Their birds and insects
present just that amount of specialisation and diversity from continental
forms which may be well explained by the known means of dispersal acting
through long periods; their land shells indicate greater isolation, owing
to their admittedly less effective means of conveyance across the ocean;
while their plants show most clearly the effects of those changes of
conditions which we have reason to believe have occurred during the
Tertiary epoch, and preserve to us in highly specialised and archaic forms
some record of the primeval immigration by which the islands were
originally {330} clothed with vegetation. But in every case the series of
forms of life in these islands is scanty and imperfect as compared with far
less favourable continental areas, and no one of them presents such an
assemblage of animals or plants as we always find in an island which we
know has once formed part of a continent.
It is still more important to note that none of these oceanic archipelagoes
present us with a single type which we may suppose to have been preserved
from Mesozoic times; and this fact, taken in connection with the volcanic
or coralline origin of all of them, powerfully enforces the conclusion at
which we have arrived in the earlier portion of this volume, that during
the whole period of geologic time as indicated by the fossiliferous rocks,
our continents and oceans have, speaking broadly, been permanent features
of our earth's surface. For had it been otherwise--had sea and land changed
place repeatedly as was once supposed--had our deepest oceans been the seat
of great continents while the site of our present continents was occupied
by an oceanic abyss--is it possible to imagine that no fragments of such
continents would remain in the present oceans, bringing down to us some of
their ancient forms of life preserved with but little change? The
correlative facts, that the islands of our great oceans are all volcanic
(or coralline built probably upon degraded volcanic islands or extinct
submarine volcanoes), and that their productions are all more or less
clearly related to the existing inhabitants of the nearest continents, are
hardly consistent with any other theory than the permanence of our oceanic
and continental areas.
We may here refer to the one apparent exception, which, however, lends
additional force to the argument. New Zealand is sometimes classed as an
oceanic island, but it is not so really; and we shall discuss its
peculiarities and probable origin further on.
* * * * *
{331}
CHAPTER XVI
CONTINENTAL ISLANDS OF RECENT ORIGIN: GREAT BRITAIN
Characteristic Features of Recent Continental Islands--Recent Physical
Changes of the British Isles--Proofs of Former Elevation--Submerged
Forests--Buried River Channels--Time of Last Union with the
Continent--Why Britain is poor in Species--Peculiar British
Birds--Freshwater Fishes--Cause of Great Speciality in Fishes--Peculiar
British Insects--Lepidoptera Confined to the British
Isles--Peculiarities of the Isle of Man--Lepidoptera--Coleoptera
confined to the British Isles--Trichoptera Peculiar to the British
Isles--Land and Freshwater Shells--Peculiarities of the British
Flora--Peculiarities of the Irish Flora--Peculiar British Mosses and
Hepaticae--Concluding Remarks on the Peculiarities of the British Fauna
and Flora.
We now proceed to examine those islands which are the very reverse of the
"oceanic" class, being fragments of continents or of larger islands from
which they have been separated, by subsidence of the intervening land at a
period which, geologically, must be considered recent. Such islands are
always still connected with their parent land by a shallow sea, usually
indeed not exceeding a hundred fathoms deep; they always possess mammalia
and reptiles either wholly or in large proportion identical with those of
the mainland; while their entire flora and fauna is characterised either by
the total absence or comparative scarcity of those endemic or peculiar
species and genera which are so striking a feature of almost all oceanic
islands. Such islands will, of course, differ from each {332} other in
size, in antiquity, and in the richness of their respective faunas, as well
as in their distance from the parent land and the facilities for
intercommunication with it; and these diversities of conditions will
manifest themselves in the greater or less amount of speciality of their
animal productions.
This speciality, when it exists, may have been brought about in two ways. A
species or even a genus may on a continent have had a very limited area of
distribution, and this area may be wholly or almost wholly contained in the
separated portion or island, to which it will henceforth be peculiar. Even
when the area occupied by a species is pretty equally divided at the time
of separation between the island and the continent, it may happen that it
will become extinct on the latter, while it may survive on the former,
because the limited number of individuals after division may be unable to
maintain themselves against the severer competition or more contrasted
climate of the continent, while they may flourish, under the more
favourable insular conditions. On the other hand, when a species continues
to exist in both areas, it may on the island be subjected to some
modifications by the altered conditions, and may thus come to present
characters which differentiate it from its continental allies and
constitute it a new species. We shall in the course of our survey meet with
cases illustrative of both these processes.
The best examples of recent continental islands are Great Britain and
Ireland, Japan, Formosa, and the larger Malay Islands, especially Borneo,
Java, and Celebes; and as each of these presents special features of
interest, we will give a short outline of their zoology and past history in
relation to that of the continents from which they have recently been
separated, commencing with our own islands, to which the present chapter
will be devoted.
_Recent Physical Changes in the British Isles._--Great Britain is perhaps
the most typical example of a large and recent continental island now to be
found upon the globe. It is joined to the Continent by a shallow bank which
extends from Denmark to the Bay of Biscay, the 100 fathom line from these
extreme points receding from the {333} coasts so as to include the whole of
the British Isles and about fifty miles beyond them to the westward. (_See_
Map.)
[Illustration: MAP SHOWING THE SHALLOW BANK CONNECTING THE BRITISH ISLES
WITH THE CONTINENT.]
The light tint indicates a depth of less than 100 fathoms.
The figures show the depth in fathoms.
The narrow channel between Norway and Denmark is 2,580 feet deep.
Beyond this line the sea deepens rapidly to the 500 and 1,000 fathom lines,
the distance between 100 and 1,000 {334} fathoms being from twenty to fifty
miles, except where there is a great outward curve to include the Porcupine
Bank 170 miles west of Galway, and to the north-west of Caithness where a
narrow ridge less than 500 fathoms below the surface joins the extensive
bank under 300 fathoms, on which are situated the Faroe Islands and
Iceland, and which stretches across to Greenland. In the North Channel
between Ireland and Scotland, and in the Minch between the outer Hebrides
and Skye, are a series of hollows in the sea-bottom from 100 to 150 fathoms
deep. These correspond exactly to the points between the opposing highlands
where the greatest accumulations of ice would necessarily occur during the
glacial epoch, and they may well be termed submarine lakes, of exactly the
same nature as those which occur in similar positions on land.
_Proofs of Former Elevation--Submerged Forests._--What renders Britain
particularly instructive as an example of a recent continental island is
the amount of direct evidence that exists, of several distinct kinds,
showing that the land has been sufficiently elevated (or the sea depressed)
to unite it with the Continent,--and this at a very recent period. The
first class of evidence is the existence, all round our coasts, of the
remains of submarine forests often extending far below the present
low-water mark. Such are the submerged forests near Torquay in Devonshire,
and near Falmouth in Cornwall, both containing stumps of trees in their
natural position rooted in the soil, with deposits of peat, branches, and
nuts, and often with remains of insects and other land animals. These occur
in very different conditions and situations, and some have been explained
by changes in the height of the tide, or by pebble banks shutting out the
tidal waters from estuaries; but there are numerous examples to which such
hypotheses cannot apply, and which can only be explained by an actual
subsidence of the land (or rise of the sea-level) since the trees grew.
We cannot give a better idea of these forests than by quoting the following
account by Mr. Pengelly of a visit to one which had been exposed by a
violent storm on the coast of Devonshire, at Blackpool near Dartmouth:--
{335}
"We were so fortunate as to reach the beach at spring-tide low-water, and
to find, admirably exposed, by far the finest example of a submerged forest
which I have ever seen. It occupied a rectangular area, extending from the
small river or stream at the western end of the inlet, about one furlong
eastward; and from the low-water line thirty yards up the strand. The lower
or seaward portion of the forest area, occupying about two-thirds of its
entire breadth, consisted of a brownish drab-coloured clay, which was
crowded with vegetable _debris_, such as small twigs, leaves, and nuts.
There were also numerous prostrate trunks and branches of trees, lying
partly imbedded in the clay, without anything like a prevalent direction.
The trunks varied from six inches to upwards of two feet in diameter. Much
of the wood was found to have a reddish or bright pink hue, when fresh
surfaces were exposed. Some of it, as well as many of the twigs, had almost
become a sort of ligneous pulp, while other examples were firm, and gave a
sharp crackling sound on being broken. Several large stumps projected above
the clay in a vertical direction, and sent roots and rootlets into the soil
in all directions and to considerable distances. It was obvious that the
movement by which the submergence was effected had been so uniform as not
to destroy the approximate horizontality of the old forest ground. One fine
example was noted of a large prostrate trunk having its roots still
attached, some of them sticking up above the clay, while others were buried
in it. Hazelnuts were extremely abundant--some entire, others broken, and
some obviously gnawed.... It has been stated that the forest area reached
the spring-tide low-water line; hence as the greatest tidal range on this
coast amounts to eighteen feet, we are warranted in inferring that the
subsidence amounted to eighteen feet as a minimum, even if we suppose that
some of the trees grew in a soil the surface of which was not above the
level of high water. There is satisfactory evidence that in Torbay it was
not less than forty feet, and that in Falmouth Harbour it amounted to at
least sixty-seven feet."[79]
{336}
On the coast of the Bristol Channel similar deposits occur, as well as
along much of the coast of Wales and in Holyhead Harbour. It is believed by
geologists that the whole Bristol Channel was, at a comparatively recent
period, an extensive plain, through which flowed the River Severn; for in
addition to the evidence of submerged forests there are on the coast of
Glamorganshire numerous caves and fissures in the face of high sea cliffs,
in one of which no less than a thousand antlers of the reindeer were found,
the remains of animals which had been devoured there by bears and hyaenas;
facts which can only be explained by the existence of some extent of dry
land stretching seaward from the present cliffs, but since submerged and
washed away. This plain may have continued down to very recent times, since
the whole of the Bristol Channel to beyond Lundy Island is under
twenty-five fathoms deep. In the east of England we have a similar
forest-bed at Cromer in Norfolk; and in the north of Holland an old land
surface has been found fifty-six feet below high-water mark.
_Buried River Channels._--Still more remarkable are the buried river
channels which have been traced on many parts of our coasts. In order to
facilitate the study of the glacial deposits of Scotland, Dr. James Croll
obtained the details of about 250 bores put down in all parts of the mining
districts of Scotland for the purpose of discovering minerals.[80] These
revealed the interesting fact that there are ancient valleys and river
channels at depths of from 100 to 260 feet below the present sea-level.
These old rivers sometimes run in quite different directions from the
present lines of drainage, connecting what are now distinct valleys; and
they are so completely filled up and hidden by boulder clay, drift, and
sands, that there is no indication of their presence on the surface, which
often consists of mounds or low hills more than 100 feet high. One of these
old valleys connects the Clyde near Dumbarton with the Forth at
Grangemouth, and appears to have contained two streams flowing in opposite
directions from a watershed about midway at Kilsith. At {337} Grangemouth
the old channel is 260 feet below the sea-level. The watershed at Kilsith
is now 160 feet above the sea, the old valley bottom being 120 feet deep or
forty feet above the sea. In some places the old valley was a ravine with
precipitous rocky walls, which have been found in mining excavations. Sir
A. Geikie, who has himself discovered many similar buried valleys, is of
opinion that "they unquestionably belong to the period of the boulder
clay."
We have here a clear proof that, when these rivers were formed, the land
must have stood in relation to the sea _at least_ 260 feet higher than it
does now, and probably much more; and this is sufficient to join England to
the continent. Supporting this evidence, we have freshwater or littoral
shells found at great depths off our coasts. Mr. Godwin Austen records the
dredging up of a freshwater shell (_Unio pictorum_) off the mouth of the
English Channel between the fifty fathom and 100 fathom lines, while in the
same locality gravel banks with littoral shells now lie under sixty or
seventy fathoms water.[81] More recently Mr. Gwyn Jeffreys has recorded the
discovery of eight species of fossil arctic shells off the Shetland Isles
in about ninety fathoms water, all being characteristic shallow water
species, so that their association at this great depth is a distinct
indication of considerable subsidence.[82]
_Time of Last Union with the Continent._--The period when this last union
with the continent took place was comparatively recent, as shown by the
identity of the shells with living species, and the fact that the buried
river channels are all covered with clays and gravels of the glacial
period, of such a character as to indicate that most of them were deposited
above the sea-level. From these and various other indications geologists
are all agreed that the last continental period, as it is called, was
subsequent to the greatest development of the ice, but probably before the
cold epoch had wholly passed away. But if so recent, we should naturally
expect our land still {338} to show an almost perfect community with the
adjacent parts of the continent in its natural productions; and such is
found to be the case. All the higher and more perfectly organised animals
are, with but few exceptions, identical with those of France and Germany;
while the few species still considered to be peculiar may be accounted for
either by an original local distribution, by preservation here owing to
favourable insular conditions, or by slight modifications having been
caused by these conditions resulting in a local race, sub-species, or
species.
_Why Britain is Poor in Species._--The former union of our islands with the
continent, is not, however, the only recent change they have undergone.
There have been partial submergences to the depth of from one hundred to
perhaps three hundred feet over a large part of our country; while during
the period of maximum glaciation the whole area north of the Thames was
buried in snow and ice. Even the south of England must have suffered the
rigour of an almost arctic climate, since Mr. Clement Reid has shown that
floating ice brought granite blocks from the Channel Islands to the coast
of Sussex. Such conditions must have almost exterminated our preexisting
fauna and flora, and it was only during the subsequent union of Britain
with the continent that the bulk of existing animals and plants could have
entered our islands. We know that just before and during the glacial period
we possessed a fauna almost or quite identical with that of adjacent parts
of the continent and equally rich in species. The glaciation and
submergence destroyed much of this fauna; and the permanent change of
climate on the passing away of the glacial conditions appears to have led
to the extinction or migration of many species in the adjacent continental
areas, where they were succeeded by the assemblage of animals now occupying
Central Europe. When England became continental, these entered our country;
but sufficient time does not seem to have elapsed for the migration to have
been completed before subsidence again occurred, cutting off the further
influx of purely terrestrial animals, and leaving us without the number of
species which our favourable climate and varied surface entitle us to.
{339}
To this cause we must impute our comparative poverty in mammalia and
reptiles--more marked in the latter than the former, owing to their lower
vital activity and smaller powers of dispersal. Germany, for example,
possesses nearly ninety species of land mammalia, and even Scandinavia
about sixty, while Britain has only forty, and Ireland only twenty-two. The
depth of the Irish Sea being somewhat greater than that of the German
Ocean, the connecting land would there probably be of small extent and of
less duration, thus offering an additional barrier to migration, whence has
arisen the comparative zoological poverty of Ireland. This poverty attains
its maximum in the reptiles, as shown by the following figures:--
Belgium has 22 species of reptiles and amphibia.
Britain ,, 13 ,, ,, ,,
Ireland ,, 4 ,, ,, ,,
Where the power of flight existed, and thus the period of migration was
prolonged, the difference is less marked; so that Ireland has seven bats to
twelve in Britain, and about 110 as against 130 land-birds.
Plants, which have considerable facilities for passing over the sea, are
somewhat intermediate in proportionate numbers, there being about 970
flowering plants and ferns in Ireland to 1,425 in Great Britain,--or almost
exactly two-thirds, a proportion intermediate between that presented by the
birds and the mammalia.
_Peculiar British Birds._--Among our native mammalia, reptiles, and
amphibia, it is the opinion of the best authorities that we possess neither
a distinct species nor distinguishable variety. In birds, however, the case
is different, since some of our species, in particular our coal-tit and
long-tailed tit, present well-marked differences of colour as compared with
continental specimens; and in Mr. Dresser's work on the _Birds of Europe_
they are considered to be distinct species, while Professor Newton, in his
new edition of Yarrell's _British Birds_, does not consider the difference
to be sufficiently great or sufficiently constant to warrant this, and
therefore classes {340} them as insular races of the continental species.
We have, however, one undoubted case of a bird peculiar to the British
Isles, in the red grouse (_Lagopus scoticus_), which abounds in Scotland,
Ireland, the north of England, and Wales, and is very distinct from any
continental species, although closely allied to the willow grouse of
Scandinavia. This latter species resembles it considerably in its summer
plumage, but becomes pure white in winter; whereas our species retains its
dark plumage throughout the year, becoming even darker in winter than in
summer. We have here therefore a most interesting example of an insular
form in our own country; but it is difficult to determine how it
originated. On the one hand, it may be an old continental species which
during the glacial epoch found a refuge here when driven from its native
haunts by the advancing ice; or, on the other hand, it may be a descendant
of the Northern willow grouse, which has lost its power of turning white in
winter owing to its long residence in the lowlands of an island where there
is little permanent snow, and where assimilation in colour to the heather
among which it lurks is at all times its best protection. In either case it
is equally interesting, as the one large and handsome bird which is
peculiar to our islands notwithstanding their recent separation from the
continent.
The following is a list of the birds now held to be peculiar to the British
Isles:--
1. Parus ater, _sub. sp._ BRITANNICUS Closely allied to _P. ater_ of
the continent; a local race or
sub-species.
2. Acredula caudata, _sub. sp._ ROSEA Allied to _A. caudata_ of the
continent.
3. LAGOPUS SCOTICUS Allied to _L. albus_ of
Scandinavia, a distinct species.
_Freshwater Fishes._--Although the productions of fresh waters have
generally, as Mr. Darwin has shown, a wide range, fishes appear to form an
exception, many of them being extremely limited in distribution. Some are
confined to particular river valleys or even to single rivers, others
inhabit the lakes of a limited district only, while some are {341} confined
to single lakes, often of small area, and these latter offer examples of
the most restricted distribution of any organisms whatever. Cases of this
kind are found in our own islands, and deserve our especial attention. It
has long been known that some of our lakes possessed peculiar species of
trout and charr, but how far these were unknown on the continent, and how
many of those in different parts of our islands were really distinct, had
not been ascertained till Dr. Guenther, so well known for his extensive
knowledge of the species of fishes, obtained numerous specimens from every
part of the country, and by comparison with all known continental species
determined their specific differences. The striking and unexpected result
has thus been attained, that no less than fifteen well-marked species of
freshwater fishes are altogether peculiar to the British Islands. The
following is the list, with their English names and localities:--[83]
_Freshwater Fishes peculiar to the British Isles._
_Latin Name._ | _English Name._ | _Locality._
| |
1. SALMO BRACHYPOMA |Short-headed salmon|Firth of Forth, Tweed,
| |Ouse.
| |
2. ,, GALLIVENSIS |Galway sea-trout |Galway, West Ireland.
| |
3. ,, ORCADENSIS |Loch Stennis trout |Lakes of Orkney.
| |
4. ,, FEROX |Great lake trout |Larger lakes of Scotland,
| |Ireland, the N. of England,
| |and Wales.
| |
5. ,, STOMACHICUS |Gillaroo trout |Lakes of Ireland.
| |
6. ,, NIGRIPINNIS |Black-finned trout |Mountain lochs of Wales
| |and Scotland.
| |
7. ,, LEVENENSIS |Loch Leven Trout |Loch Leven, Loch Lomond,
| |Windermere.
| |
8. ,, PERISII |Welsh charr |Llanberris lakes, N.
| |Wales.
| |
9. ,, WILLUGHBII |Windermere charr |Lake Windermere and
| |others in N. of England,
| |and Lake Bruiach in
| |Scotland.
| |
10. ,, KILLINENSIS |Lock Killin charr |Killin lake in
| |Inverness-shire.
| |
11. ,, COLII |Cole's charr |Lough Eske and Lough
| |Dan, Ireland.
| |
12. ,, GRAYI |Gray's charr |Lough Melvin, Leitrim,
| |N.W. Ireland.
| |
{342}
13. COREGONUS CLUPEOIDES |The gwyniad, or |Loch Lomond, Ulleswater,
|schelly |Derwentwater,
| |Haweswater, and Bala
| |lake.
| |
14. ,, VANDESIUS |The vendace |Loch Maben, Dumfriesshire.
| |
15. ,, POLLAN |The pollan |Lough Neagh and Lough
| |Earne, N. of Ireland.
These fifteen peculiar fishes differ from each other and from all British
and continental species, not in colour only, but in such important
structural characters as the number and size of the scales, form and size
of the fins, and the form or proportions of the head, body, or tail. Some
of them, like _S. killinensis_ and the Coregoni are in fact, as Dr.
Guenther assures me, just as good and distinct species as any other
recognised species of fish. It may indeed be objected that, until all the
small lakes of Scandinavia are explored, and their fishes compared with
ours, we cannot be sure that we have any peculiar species. But this
objection has very little weight if we consider how our own species vary
from lake to lake and from island to island, so that the Orkney species is
not found in Scotland, and only one of the peculiar British species extends
to Ireland, which has no less than five species altogether peculiar to it.
If the species of our own two islands are thus distinct, what reason have
we for believing that they will be otherwise than distinct from those of
Scandinavia? At all events, with the amount of evidence we already possess
of the very restricted ranges of many of our species, we must certainly
hold them to be peculiar till they have been proved to be otherwise.
The great speciality of the Irish fishes is very interesting, because it is
just what we should expect on the theory of evolution. In Ireland the two
main causes of specific change--isolation and altered conditions--are each
more powerful than in Britain. Whatever difficulty continental fishes may
have in passing over to Britain, that difficulty will certainly be
increased by the second sea passage to Ireland; and the latter country has
been longer isolated, for the Irish Sea with its northern and southern
channels is considerably deeper than the German Ocean and the {343} Eastern
half of the English Channel, so that, when the last subsidence occurred,
Ireland would have been an island for some length of time while England and
Scotland still formed part of the continent. Again, whatever differences
have been produced by the exceptional climate of our islands will have been
greater in Ireland, where insular conditions are at a maximum, the
abundance of moisture and the equability of temperature being far more
pronounced than in any other part of Europe.
Among the remarkable instances of limited distribution afforded by these
fishes, we have the Loch Stennis trout confined to the little group of
lakes in the mainland of Orkney, occupying altogether an area of about ten
miles by three; the Welsh charr confined to the Llanberris lakes, about
three miles in length; Gray's charr confined to Lough Melvin, about seven
miles long; while the Loch Killin charr, known only from a small mountain
lake in Inverness-shire, and the vendace, from the equally small lakes at
Loch Maben in Scotland, are two examples of restricted distribution which
can hardly be surpassed.
_Cause of Great Speciality in Fishes._--The reason why fishes alone should
exhibit such remarkable local modifications in lakes and islands is
sufficiently obvious. It is due to the extreme rarity of their transmission
from one lake to another. Just as we found to be the case in Oceanic
Islands, where the means of transmission were ample hardly any modification
of species occurred, while where these means were deficient and individuals
once transported remained isolated during a long succession of ages, their
forms and characters became so much changed as to bring about what we term
distinct species or even distinct genera,--so these lake fishes have become
modified because the means by which they are enabled to migrate so rarely
occur. It is quite in accordance with this view that some of the smaller
lakes contain no fishes, because none have ever been conveyed to them.
Others contain several; and some fishes which have peculiarities of
constitution or habits which render their transmission somewhat less
difficult occur in several lakes over a wide area of country, though only
one appears to be common to the British and Irish lakes. {344}
The manner in which fishes are enabled to migrate from lake to lake is
unknown, but many suggestions have been made. It is a fact that whirlwinds
and waterspouts sometimes carry living fish in considerable numbers and
drop them on the land. Here is one mode which might certainly have acted
now and then in the course of thousands of years, and the eggs of fishes
may have been carried with even greater ease. Again we may well suppose
that some of these fish have once inhabited the streams that enter or flow
out of the lakes as well as the lakes themselves; and this opens a wide
field for conjecture as to modes of migration, because we know that rivers
have sometimes changed their courses to such an extent as to form a union
with distinct river basins. This has been effected either by floods rising
over low watersheds, by elevations of the land changing lines of drainage,
or by ice blocking up valleys and compelling the streams to flow over
watersheds to find an outlet. This is known to have occurred during the
glacial epoch, and is especially manifest in the case of the Parallel Roads
of Glenroy, and it probably affords the true solution of many of the cases
in which existing species of fish inhabit distinct river basins whether in
streams or lakes. If a fish thus wandered out of one river-basin into
another, it might then retire up the streams to some of the lakes, where
alone it might find conditions favourable to it. By a combination of the
modes of migration here indicated it is not difficult to understand how so
many species are now common to the lakes of Wales, Cumberland, and
Scotland, while others less able to adapt themselves to different
conditions have survived only in one or two lakes in a single district; or
these last may have been originally identical with other forms, but have
become modified by the particular conditions of the lake in which they have
found themselves isolated.
_Peculiar British Insects._--We now come to the class of insects, and here
we have much more difficulty in determining what are the actual facts,
because new species are still being yearly discovered and considerable
portions of Europe are but imperfectly explored. It often happens that an
insect is discovered in our islands, and for some {345} years Britain is
its only recorded locality; but at length it is found on some part of the
continent, and not unfrequently has been all the time known there, but
disguised by another name, or by being classed as a variety of some other
species. This has occurred so often that our best entomologists have come
to take it for granted that _all_ our supposed peculiar British species are
really natives of the continent and will one day be found there; and owing
to this feeling little trouble has been taken to bring together the names
of such as from time to time remain known from this country only. The view
of the probable identity of our entire insect-fauna with that of the
continent has been held by such well-known authorities as the late Mr.
E. C. Rye and Dr. D. Sharp for the beetles, and by Mr. H. T. Stainton for
butterflies and moths; but as we have already seen that among two orders of
vertebrates--birds and fishes--there are undoubtedly peculiar British
species, it seems to me that all the probabilities are in favour of there
being a much larger number of peculiar species of insects. In every other
island where some of the vertebrates are peculiar--as in the Azores, the
Canaries, the Andaman Islands, and Ceylon--the insects show an equal if not
a higher proportion of speciality, and there seems no reason whatever why
the same law should not apply to us. Our climate is undoubtedly very
distinct from that of any part of the continent, and in Scotland, Ireland,
and Wales we possess extensive tracts of wild mountainous country where a
moist uniform climate, an alpine or northern vegetation, and a considerable
amount of isolation, offer all the conditions requisite for the
preservation of some species which may have become extinct elsewhere, and
for the slight modification of others since our last separation from the
continent. I think, therefore, that it will be very interesting to take
stock, as it were, of our recorded peculiarities in the insect world, for
it is only by so doing that we can hope to arrive at any correct solution
of the question on which there is at present so much difference of opinion.
For the list of Coleoptera with the accompanying notes I was originally
indebted to the late Mr. E. C. Rye; and Dr. Sharp also gave me valuable
information as to the recent {346} occurrence of some of the supposed
peculiar species on the continent. The list has now been revised by the
Rev. Canon Fowler, author of the best modern work on the British
Coleoptera, who has kindly furnished some valuable notes.
For the Lepidoptera I first noted all the species and varieties marked as
British only in Staudinger's Catalogue of European Lepidoptera. This list
was carefully corrected by Mr. Stainton, who weeded out all the species
known by him to have been since discovered, and furnished me with valuable
information on the distribution and habits of the species. This information
often has a direct bearing on the probability of the insect being peculiar
to Britain, and in some cases may be said to explain why it should be so.
For example, the larvae of some of our peculiar species of Tineina feed
during the winter, which they are enabled to do owing to our mild and
insular climate, but which the severer continental winters render
impossible. A curious example of the effect this habit may have on
distribution is afforded by one of our commonest British species,
_Elachista rufocinerea_, the larva of which mines in the leaves of _Holcus
mollis_ and other grasses from December to March. This species, though
common everywhere with us, extending to Scotland and Ireland, is quite
unknown in similar latitudes on the continent, but appears again in Italy,
the South of France, and Dalmatia, where the mild winters enable it to live
in its accustomed manner.
Such cases as this afford an excellent illustration of those changes of
distribution, dependent probably on recent changes of climate, which may
have led to the restriction of certain species to our islands. For should
any change of climate lead to the extinction of the species in South
Europe, where it is far less abundant than with us, we should have a common
and wide-spread species entirely restricted to our islands. Other species
feed in the larva state on our common gorse, a plant found only in limited
portions of Western and Southern Europe; and the presence of this plant in
a mild and insular climate such as ours may well be supposed to have led to
the preservation of some of the numerous species which are or have been
dependent on it. Since the first edition was {347} published many new
British species have been discovered, while some of the supposed peculiar
species have been found on the continent. Information as to these has been
kindly furnished by Mr. W. Warren, Mr. C. G. Barrett, Lord Walsingham, and
other students of British Lepidoptera, and the first-named gentleman has
also looked over the proofs.
Mr. McLachlan has kindly furnished me with some valuable information on
certain species of Trichoptera or Caddis flies which seem to be peculiar to
our islands; and this completes the list of orders which have been studied
with sufficient care to afford materials for such a comparison. We will now
give the list of peculiar British Insects, beginning with the Lepidoptera
and adding such notes as have been supplied by the gentlemen already
referred to.
_List of the Species or Varieties of Lepidoptera which, so far as at
present known, are confined to the British Islands. (The figures show the
dates when the species was first described. Species added since the first
edition are marked with an asterisk.)_
DIURNI.
1. POLYOMMATUS DISPAR. "The large copper." This fine insect, once
common in the fens, but now extinct owing to extensive drainage, is
generally admitted to be peculiar to our island, at all events as a
variety or local form. Its continental ally differs constantly in being
smaller and in having smaller spots; but the difference, though
constant, is so slight that it is now classed as a variety under the
name of _rutilus_. Our insect may therefore be stated to be a
well-marked local form of a continental species.
2. Lycaena astrarche, _var._ ARTAXERXES. This very distinct form is
confined to Scotland and the north of England. The species of which it
is considered a variety (more generally known to English entomologists
as _P. agestis_) is found in the southern half of England, and almost
everywhere on the continent.
BOMBYCES.
3. Lithosia complana, _var._ SERICEA. North of England (1861).
4. Hepialus humuli, _var._ HETHLANDICA. Shetland Islands (1865). A
remarkable form, in which the male is usually yellow and buff instead
of pure white, as in the common form, but exceedingly variable in tint
and markings.
5. EPICHNOPTERYX RETICELLA. Sheerness, Gravesend, and other localities
along the Thames (1847); Hayling Island, Sussex.
6. E. pulla, _var._ RADIELLA. Near London, rare (1830?); the species in
Central and Southern Europe. (Doubtfully peculiar in Mr. Stainton's
opinion.) {348}
NOCTUAE.
7. Acronycta euphorbiae, _var._ MYRICAE. Scotland only (1852). A
melanic form of a continental species.
8. AGROTIS SUBROSEA. Cambridgeshire and Huntingdonshire fens, perhaps
extinct (1835). The _var._ _subcaerulea_ is found in Finland and
Livonia.
9. Agrotis candelarum _var._ ASHWORTHII. South and West (1855).
Distinct and not uncommon.
10. Luperina luteago, _var._ BARRETTI. Ireland (1864).
11. Aporophyla australis, _var._ PASCUEA. South of England (1830). A
variety of a species otherwise confined to South Europe.
12. Hydraecia nictitans, _var._ PALUDRIS.
GEOMETRAE.
13. Boarmia gemmaria, _var._ PERFUMARIA. Near London and elsewhere. A
large dark variety of a common species.
14. *B. repandata, _var._ SODORENSIUM. Outer Hebrides.
15. *Emmelesia albulata, _var._ HEBRIDIUM. Outer Hebrides.
16. *E. albulata, _var._ THULES. Shetland Islands.
17. *Melanippe montanata, _var._ SHETLANDICA. Shetland Islands.
18. *M. sociata, _var._ OBSCURATA. Outer Hebrides. A dark form.
19. Cidaria albulata, _var._ GRISEATA. East of England (1835). A
variety of a species otherwise confined to Central and Southern Europe.
20. EUPITHECIA CONSTRICTATA.. Widely spread, but local (1835). Larva on
thyme.
21. *E. satyrata, _var._ CURZONI. N. Scotland.
22. *E. nanata _var._ CURZONI. Shetland Islands.
PYRALIDINA.
23. Aglossa pinguinalis, _var._ STREATFIELDI. Mendip Hills (1830). A
remarkable variety of the common "tabby."
24. *Scoparia cembrae, _var._ SCOTICA. Scotland (1872).
25. *Myelois ceratoniae, _var._ PRYERELLA. North London (1871).
26. *Howoeosoma nimbella, _var._ SAXICOLA. England, Scotland, Isle of
Man (1871).
27. *Epischnia bankesiella. Isle of Portland (1888).
TORTRICINA.
28. APHELIA NIGROVITTANA. Scotland (1852). A local form of the
generally distributed _A. lanceolana_.
29. GRAPHOLITA PARVULANA. Isle of Wight (1858). Rare. A distinct
species.
30. CONCHYLIS ERIGERANA. South-east of England (1866).
31. *BRACHYTAENIA WOODIANA. Herefordshire (1882).
32. *Eupoecilia angustana, _var._ THULEANA. Shetland Islands.
33. *TORTRIX DONELANA. Connemara, Ireland (1890).
TINEINA.
34. TINEA COCHYLIDELLA. Sanderstead, near Croydon (1854). Unique!
35. ACROLEPIA BETULAETELLA. Yorkshire and Durham (1840). Rare.
36. ARGYRESTHIA SEMIFUSCA. North and West of England (1829). Rather
scarce. A distinct species.
37. GELECHIA DIVISELLA. A fen insect (1856). Rare. {349}
38. G. CELERELLA. West of England (1854). A doubtful species.
39. *G. TETRAGONELLA. Yorkshire. Norfolk. Salt marshes.
40. *G. SPARSICILIELLA. Pembroke.
41. *G. PLANTAGINELLA. A salt-marsh species.
42. G. OCELLATELLA (Barrett _nec_ Stainton). Bred from _Beta maritima_.
Very distinct.
43. BRYOTROPHA POLITELLA. Moors of North of England. Norfolk (1854).
44. *B. PORTLANDICELLA. Isle of Portland (1890).
45. LITA FRATERNELLA. Widely scattered (1834). Larva feeds on shoots of
_Stellaria uliginosa_ in spring.
46. L. BLANDULELLA. Kent.
47. ANACAMPSIS SIRCOMELLA. North and West England (1854). Perhaps a
melanic variety of the more widely spread _A. taeniolella_.
48. A. IMMACULATELLA. West Wickham (1834). Unique! A distinct species.
49. *OECOPHORA WOODIELLA?
50. GLYPHIPTERYX CLADIELLA. Eastern Counties (1859). Abundant.
51. G. SCHOENICOLELLA. In several localities (1859).
52. GRACILARIA STRAMINEELLA. (1850). On birch. Perhaps a local form of
_G. elongella_, found on alder.
53. ORNIX LOGANELLA. Scotland (1848). Abundant, and a distinct species.
54. O. DEVONIELLA. In Devonshire (1854). Unique!
55. COLEOPHORA SATURATELLA. South of England (1850). Abundant on broom.
56. C. INFLATAE. South and East of England. On _Silene inflata._ ?
continental.
57. C. SQUAMOSELLA. Surrey (1856). Very rare, but an obscure species.
58. C. SALINELLA. On Sea-coast (1859). Abundant.
59. *C. POTENTILLAE. South of England.
60. *C. ADJUNCTELLA. Essex salt marshes. ? Lancashire (1882).
61. *C. LIMONIELLA. Isle of Wight. Feeds on _Statice limonium_.
62. ELACHISTA FLAVICOMELLA. Dublin (1856). Excessively rare, two
specimens only known.
63. *E. SCIRPI. Wales and Sussex. Salt marshes.
64. E. CONSORTELLA. Scotland (1854). A doubtful species.
65. E. MEGERLELLA. Widely distributed (1854). Common. Larva feeds in
grass during winter and early spring.
66. E. OBLIQUELLA. Near London (1854). Unique!
67. E. TRISERIATELLA. South of England (1854). Very local; an obscure
species.
68. *TINAGMA BETULAE. East Dorset (1891).
69. LITHOCOLLETIS NIGRESCENTELLA. Northumberland (1850). Rare; a dark
form of _L. Bremiella_, which is widely distributed.
70. *L. ANDERIDAE. Sussex. Dorset (1886).
71. L. IRRADIELLA. North Britain (1854). A northern form of the more
southern and wide-spread _L. lautella_.
72. L. TRIGUTTELLA. Sanderstead, near Croydon (1848). Unique! very
peculiar.
73. L. ULICICOLELLA. In a few wide-spread localities (1854). A peculiar
form.
74. L. CALEDONIELLA. North Britain (1854). A local variety of the more
widespread _L. corylifoliella_. {350}
75. L. DUNNINGIELLA. North of England (1852). A somewhat doubtful
species.
76. BUCCULATRIX DEMARYELLA. Widely distributed (1848). Rather common.
77. TRIFURCULA SQUAMATELLA. South of England (1854). A doubtful
species.
78. NEPTICULA IGNOBILIELLA. Widely scattered (1854). On hawthorn, not
common. ? on continent.
79. N. POTERII. South of England (1858). Bred from Larvae in _Poterium
sanguisorba_.
80. N. QUINQUELLA. South of England (1848). On oak leaves, very local.
? continental.
81. N. APICELLA. Local (1854). Probably confused with allied species on
the continent.
82. N. HEADLEYELLA. Local (1854). A rare species.
83. *N. HODGKINSONI. Lancashire.
84. *N. WOOLHOPIELLA. Herefordshire.
85. *N. SERELLA. Westmoreland and S. England.
86. *N. AUROMARGINELLA. Dorset (1890).
87. *MICROPTERYX SANGII. (1891).
88. *M. SALOPIELLA.
PTEROPHORINA.
89. AGDISTIS BENNETTI. East coast. I. of Wight (1840). Common on
_Statice limonium_.
We have here a list of eighty-nine species, which, according to the best
authorities, are, in the present state of our knowledge, peculiar to
Britain. It is a curious fact that no less than fifty of these have been
described more than twenty-five years; and as during all that time they
have not been recognised on the continent, notwithstanding that good
coloured figures exist of almost all of them, it seems highly probable that
many of them are really confined to our island. At the same time we must
not apply this argument too rigidly, for the very day before my visit to
Mr. Stainton he had received a letter from Professor Zeller announcing the
discovery on the continent of a species of our last family, Pterophorina,
which for more than forty years had been considered to be exclusively
British. This insect, _Platyptilia similidactyla_ (_Pterophorus
isodactylus_, Stainton's _Manual_), had been taken rarely in the extreme
north and south of our islands--Teignmouth and Orkney, a fact which seemed
somewhat indicative of its being a straggler. Again, seven of the species
are unique, that is, have only been captured once; and it may be supposed
that, as they are so rare as to have been found only once in England, they
may be all {351} equally rare and not yet found on the continent. But this
is hardly in accordance with the laws of distribution. Widely scattered
species are generally abundant in some localities; while, when a species is
on the point of extinction, it must for a time be very rare in the single
locality where it last maintains itself. It is then more probable that some
of these unique species represent such as are almost extinct, than that
they have a wide range and are equally rare everywhere; and the peculiarity
of our insular climate, combined with our varied soil and vegetation, offer
conditions which may favour the survival of some species with us after they
have become extinct on the continent.
Of the sixty-nine species recorded in my first edition fourteen have been
since discovered on the continent, while no less than twenty-two species
and eleven varieties have been added to the list. As we can hardly suppose
continental entomologists to be less thorough collectors than ourselves, it
ought to be more and more difficult to find any insects which are unknown
on the continent if all ours really exist there; and the fact that the list
of apparently peculiar British species is an increasing one renders it
probable that many of them are not only apparently but really so. Both
general considerations dependent on the known laws of distribution, and the
peculiar habits, conspicuous appearance, and restricted range, of many of
our species, alike indicate that some considerable proportion of them will
remain permanently as peculiar British species.
We will now pass on to the Coleoptera, or beetles, an order which has been
of late years energetically collected and carefully studied by British
entomologists.
_List of the Species and Varieties of Beetles which, so far as at present
known, are confined to the British Islands. Those added since the first
edition are marked with an asterisk._
CARABIDAE.
1. *Bembidium saxatile, _var._ VECTENSIS (Fowler). Isle of Wight.
2. DROMIUS VECTENSIS (Rye). Common in the Isle of Wight, also in Kent,
and at Weymouth and Seaton. Closely allied to _D. sigma_.
3. Harpalus latus, _var._ METALLESCENS (Rye). Unique, but very marked!
South coast. "Perhaps a sport or a hybrid" (Fowler).
4. ACUPALPUS DERELICTUS (Dawson). Unique! North Kent. Canon Fowler
thinks it may be a variety of _A. dorsalis_. {352}
DYTICIDAE.
5. *Acilius sulcatus, _var._ SCOTICUS (Curtis). Scotland. A melanic
variety.
HELOPHORIDAE.
6. OCHTHEBIUS POWERI (Rye). Very marked. S. coast. A few specimens
only.
7. *O. AENEUS (Steph).
BRACHYELYTRA.
8. OCYUSA HIBERNICA (Rye). Ireland, mountain tops, and at Braemar.
9. *OXYPODA TARDA (Sharp).
10. ,, PECTITA (Sharp). Scotland.
11. ,, VERECUNDA (Sharp). Scotland, also London districts.
12. HOMALOTA DIVERSA (Sharp).
13. ,, FULVIPENNIS (Rye).
14. ,, OBLONGIUSCULA (Sharp). Scotland, also England and Ireland.
15. ,, PRINCEPS (Sharp). A coast insect.
16. ,, CURTIPENNIS (Sharp). Scotland and near Birmingham.
17. H. levana, _var._ SETIGERA (Sharp).
18. STENUS OSCILLATOR (Rye). Unique! South coast. May be a hybrid.
19. TROGOPHLAEUS SPINICOLLIS (Rye). Mersey estuary, unique! Most
distinguishable, nothing like it in Europe. Perhaps imported from
another continent.
20. EUDECTUS WHITEI (Sharp). Scotch hills. A variety of _E. Giraudi_ of
Germany (the only European species) _fide_ Kraatz (Sharp).
21. HOMALIUM RUGULIPENNE (Rye). Exceedingly marked form. Northern and
western coasts; rare.
22. *MYCETOPORUS MONTICOLA (Fowler). Cheviots and Inverness-shire.
SCYDMAENIDAE.
23. *SCYDMAENUS POWERI (Fowler) S. England. A recent discovery.
24. *S. PLANIFRONS (Fowler). ,, ,,
PSELAPHIDAE.
25. BRYAXIS COTUS (De Sauley). Scotland.
26. BYTHINUS GLABRATUS (Rye). Sussex coast; also Isle of Wight; a few
specimens; very distinguishable; myrmecophilous (lives in ants' nests).
TRICHOPTERYGIDAE.
27. PTINELLA MARIA (Matthews) Derbyshire.
28. TRICHOPTERYX SARAE ( ,, ) Notts.
29. ,, POWERI ( ,, ) Oxon.
30. ,, EDITHIA ( ,, ) Kent.
31. ,, *ANGUSTA ( ,, ) Leicestershire.
32. ,, KIRBII ( ,, ) Norfolk.
33. ,, FRATERCULA ( ,, )
34. ,, WATERHOUSII ( ,, )
35. ,, CHAMPIONIS ( ,, ) Wicken Fen.
36. ,, JANSONI ( ,, ) Leicestershire.
37. ,, SUFFOCATA (Haliday). Ireland, Co. Cork.
38. ,, CARBONARIA (Matthews). Notts.
{353} 39. Ptilium halidayi (Matthews). Sherwood Forest.
40. ,, caledonicum (Sharp). Scotland; very marked form.
41. ,, insigne (Matthews). London district.
42. *ORTHOPERUS MUNDUS (Matthews). Oxfordshire.
43. *O. PUNCTULATUS (Matthews). Lincolnshire.
ANISOTOMIDAE.
44. AGATHIDIUM RHINOCEROS (Sharp). Old fir-woods in Perthshire; local,
many specimens; a very marked species.
45. ANISOTOMA SIMILATA (Rye). South of England. Two specimens.
46. ,, LUNICOLLIS (Rye). North-east and South of England, a very
marked form; several specimens.
PHALACRIDAE.
47. PHALACRUS BRISOUTI (Rye). South of England. Rare. "Perhaps a small
form of _P. coruscus_" (Fowler).
CRYPTOPHAGIDAE.
48. ATOMARIA DIVISA (Rye). Unique! South of England.
LATHRIDIIDAE.
49. Melanopthalma transversalis, _var._ WOLLASTONI (Waterhouse). South
coast, and Lincolnshire.
BYRRHIDAE.
50. SYNCALYPTA HIRSUTA (Sharp). South of England, local. "Closely
allied to _S. setigera_" (Fowler).
MORDELLIDAE.
51. *ANASPIS SEPTENTRIONALIS. Scotland (1891). (Champion.)
52. * ,, GARNEYSI (Fowler). London District. (1890.)
TELEPHORIDAE.
53. TELEPHORUS DARWINIANUS (Sharp). Scotland, sea-coast. A stunted form
of abnormal habits. Perhaps a variety of _T. lituratus_.
CYPHONIDAE.
54. CYPHON PUNCTIPENNIS (Sharp). Scotland.
ANTHICIDAE.
55. ANTHICUS SALINUS (Crotch). South coast.
56. ,, SCOTICUS (Rye). Loch Leven; very distinct; many specimens.
CIOIDAE.
57. *CIS BILAMELLATUS (Wood). West Wickham, Kent. "Perhaps imported.
Has the appearance of an exotic Cis" (Fowler).
TOMICIDAE.
58. *Pityopthorus lichtensteinii, _var._ SCOTICUS (Blandford).
Scotland.
CURCULIONIDAE.
59. Ceuthorhynchus contractus, _var._ PALLIPES (Crotch). Lundy Island;
several specimens. A curious variety only known from this island.
60. LIOSOMUS TROGLODYTES (Rye). A very queer form. Two or three
specimens. South of England.
61. *Orcheites ilicis, _var._ NIGRIPES (Fowler). London District.
(1890.)
{354}
62. APION RYEI (Blackburn). Shetland Islands. Several specimens.
Perhaps a _var._ of _A. fagi_.
CHRYSOMELIDAE.
63. Chrysomela staphylea, _var._ SHARPI (Fowler). Solway district.
HALTICIDAE.
64. LONGITARSUS AGILIS (Rye). South of England; many specimens.
65. ,, DISTINGUENDA (Rye). South of England; many specimens.
66. PSYLLIODES LURIDIPENNIS (Kutschera). Lundy Island. A very curious
form, not uncommon in this small island, to which it appears to be
confined. "An extreme and local variety of _P. chrysocephala_"
(Fowler).
COCCINELLIDAE.
67. SCYMNUS LIVIDUS (Bold). Northumberland. A doubtful species.
Of the sixty-seven species and varieties of beetles in the preceding list,
a considerable number no doubt owe their presence there to the fact that
they have not yet been discovered or recognised on the continent. This is
almost certainly the case with many of those which have been separated from
other species by very minute and obscure characters, and especially with
the excessively minute Trichopterygidae described by Mr. Matthews. There
are others, however, to which this mode of getting rid of them will not
apply, as they are so marked as to be at once recognised by any competent
entomologist, and often so plentiful that they can be easily obtained when
searched for. The peculiar species of Apion in the Shetland Islands is
interesting, and may be connected with the very peculiar climatal
conditions there prevailing, which have led in some cases to a change of
habits, so that a species of weevil (_Otiorhynchus maurus_) always found on
mountain sides in Scotland here occurs on the sea-shore. Still more curious
is the occurrence of two distinct forms (a species and a well-marked
variety) on the small granitic Lundy Island in the Bristol Channel. This
island is about three miles long and twelve from the coast of Devonshire,
consisting mainly of granite with a little of the Devonian formation, and
the presence here of peculiar insects can only be due to isolation with
special conditions, and immunity from enemies or competing forms. When we
consider the similar islands off {355} the coast of Scotland and Ireland,
with the Isle of Man and the Scilly Islands, none of which have been yet
thoroughly explored for beetles, it is probable that many similar examples
of peculiar isolated forms remain to be discovered.
Looking, then, at what seem to me the probabilities of the case from the
standpoint of evolution and natural selection, and giving due weight to the
facts of local distribution as they are actually presented to us, I am
forced to differ from the opinion held by our best entomological
authorities, and to believe that some at least, perhaps many, of the
species which, in the present state of our knowledge, appear to be peculiar
to our islands, are, not only apparently, but really, so peculiar.
I am indebted to Mr. Robert McLachlan for the following information on
certain Trichopterous Neuroptera (or caddis-flies) which appear to be
confined to our islands. The peculiar aquatic habits of the larvae of these
insects, some living in ponds or rivers, others in lakes, and others again
only in clear mountain streams, render it not improbable that some of them
should have become isolated and preserved in our islands, or that they
should be modified owing to such isolation.
_Trichoptera peculiar to the British Isles._
1. PHILOPOTAMUS INSULARIS. (? A variety of _P. montanus_.)--This can
hardly be termed a British species or variety, because, so far as at
present known, it is peculiar to the Island of Guernsey. It agrees
structurally with _P. montanus_, a species found both in Britain and on
the continent, but it differs in its strikingly yellow colour, and less
pronounced markings. All the specimens from Guernsey are alike, and
resident entomologists assured Mr. McLachlan that no other kind is
known. Strange to say, some examples from Jersey differ considerably,
resembling the common European and British form. Even should this
peculiar variety be at some future time found on the continent it would
still be a remarkable fact that the form of insect inhabiting two small
islands only twenty miles apart should constantly differ; but as Jersey
is between Guernsey and the coast, it seems just possible that the more
insular conditions, and perhaps some peculiarity of the soil and water
in the former island, have really led to the production or preservation
of a well-marked variety of insect. In the first edition of this work
two other species were named as then, peculiar to Britain--Setodes
argentipunctella and Rhyacophila munda, but both have now been taken on
the continent.
2. MESOPHYLAX IMPUNCTATUS, _var._ ZETLANDICUS.--A variety of a South
and Central European species, one specimen of which has been found in
Dumfriesshire. The variety is distinguished by its small size and dark
colour.
{356}
_Land and Freshwater Shells._--In the first edition of this work four
species were noted as being, so far as was then known, exclusively British.
Two of these, _Cyclas pisidioides_ (now called _Sphaerium pisidioides_) and
_Geomalacus maculosus_, have been discovered on the continent, but the
other two remain still apparently confined to these islands; and to these
another has been added by the discovery of a new species of Hydrobia in the
estuary of the Thames. The peculiar species now stands as follows:--
1. LIMNEA INVOLUTA.--A pond snail with a small polished amber-coloured
shell found only in a small alpine lake and its inflowing stream on
Cromagloun mountain near the lakes of Killarney. It was discovered in
1838, and has frequently been obtained since in the same locality. It
is sometimes classed as a variety of _Limnea peregra_, and is at all
events closely allied to that species.
2. HYDROBIA JENKINSII.--A small shell of the family Rissoidae
inhabiting the Thames estuary both in Essex and Kent. It was discovered
only a few years ago, and was first described in 1889.
3. ASSIMINEA GRAYANA.--A small estuarine pulmonobranch found on the
banks of the Thames between Greenwich and Gravesend, on mud at the
roots of aquatic plants. It has been discovered more than sixty years.
But besides the above-named species there are a considerable number of
well-marked varieties of shells which seem to be peculiar to our islands. A
list of these has been kindly furnished me by Mr. Theo. D. A. Cockerell,
who has paid much attention to the subject; and after omitting all those
whose peculiarities are very slight or whose absence from the continent is
doubtful, there remain a series of forms some of which are in all
probability really endemic with us. This is the more probable from the fact
that an introduced colony of _Helix nemoralis_ at Lexington, Virginia,
presents numerous varieties among which are several which do not occur in
Europe.[84] The following list is therefore given in the hope that it may
be useful in calling attention to those varieties which are not yet
positively known to occur elsewhere than in our islands, and {357} thus
lead, ultimately, to a more accurate knowledge of the facts. It is only by
obtaining a full knowledge of varieties, their distribution and their
comparative stability, that we can ever hope to detect the exact process by
which nature works in the formation of species.
LIST OF THE SPECIES AND VARIETIES OF LAND AND FRESHWATER SHELLS WHICH, SO
FAR AS AT PRESENT KNOWN, ARE BELIEVED TO BE PECULIAR TO THE BRITISH ISLES
OR NOT FOUND ON THE CONTINENT.
LIMACIDAE.
1. Limax marginatus, _var._ MACULATUS. Ireland; frequent, very
distinct.
2. ,, ,, ,, DECIPIENS. Ireland and England.
3. ,, flavus, _var._ SUFFUSUS. England; Melanic form.
4. ,, ,, ,, GRISEUS. England; Melanic form.
5. Agriolimax agrestis, _var._ NIGER. Yorkshire. Melanic. Azores.
6. ,, ,, ,, GRISEUS. England. Melanic.
7. Amalia gagates, _var._ RAVA. W. of England.
8. ,, sowerbyi, _var._ RUSTICA. England.
9. ,, ,, ,, NIGRESCENS. Surrey and Middlesex.
10. ,, ,, ,, BICOLOR. Ealing.
11. Hyalina crystallina, _var._ COMPLANATA. Near Bristol.
12. ,, fulva, _var._ ALDERI.
13. Vitrina pellucida, _var._ DEPRESSIUSCULA. S. England, Wales.
HELICIDAE.