the station of insects, have divided the globe into entomological
_climates_. Fabricius considers it as divisible into _eight_
such climates, which he denominates the _Indian_, _Egyptian_,
_Southern_, _Mediterranean_, _Northern_, _Oriental_, _Occidental_,
and _Alpine_. The first containing the tropics; the second, the
northern region immediately adjacent; the third, the southern; the
fourth, the countries bordering on the Mediterranean sea, including
also _Armenia_ and _Media_; the fifth, the northern part of Europe
interjacent between Lapland and Paris; the sixth, the northern parts
of Asia where the cold in winter is intense; the seventh, North
America, Japan, and China; and the eighth, all those mountains whose
summits are covered with eternal snow[1472]. M. Latreille objects
to this division, as too vague and arbitrary and not sufficiently
correct as to temperature; and observes, with great truth, that as
places where the temperature is the same, have different animals,
it is impossible, in the actual state of our knowledge, to fix
these distinctions of climates upon a solid basis. The different
elevations of the soil above the level of the sea, its mineralogical
composition, the varying quantity of its waters, the modifications
which the mountains, by their extent, their height, and their
direction, produce upon its temperature; the forests, larger or
smaller, with which it may be covered; the effects of neighbouring
climates upon it,--are all elements that render calculations on this
subject very complicated, and throw a great degree of uncertainty
over them[1473]. This learned Entomologist would judiciously consider
entomological climates under another view,--that which the genera of
_Arachnida_ and insects _exclusively_ appropriated to determinate
spots or regions would supply[1474]. Linné's _dictum_ with regard
to genera will here also apply; "Let the insects point out the
climate, and not the climate the insects." If you expect invariably
to find the same insects within the same parallels of latitude, you
will be sadly disappointed; for, as our author further observes,
"The totality or a very large number of _Arachnida_ and insects,
the temperature and soil of whose country are the same, but widely
separated, is in general, even if the countries are in the same
parallel, composed of different species[1475]." The natural limits of
a country,--as mountainous ranges, rivers, vast deserts, &c.,--often
also say to its insect population, "No further shall ye come;"
interposing a barrier that it never passes[1476]. Humboldt observes,
with respect to the _Simulia_ and _Culices_ of South America, that
their geographical distribution does not appear to depend solely on
the _heat_ of the climate, the excess of humidity, or the thickness
of forests; but on local circumstances that are difficult to
characterize[1477]: and Mr. W. S. MacLeay makes a similar observation
upon that of _Gymnopleurus_[1478]. So that the real insect climates,
or those in which certain groups or species appear, may be regarded
as fixed by the will of the CREATOR, rather than as certainly
regulated by any _isothermal_ lines. Still, however, under certain
limitations, it must be admitted that the temperature has much to
do with the station of insects. The increase of caloric is always
attended with a proportional increase in the number and kind of the
groups and species of these beings. If we begin within the polar
regions of ice and snow, the list is very meager. As we descend
towards the line, their numbers keep gradually increasing, till they
absolutely _swarm_ within the tropics. Something like this takes
place in miniature upon _mountains_. Tournefort long since observed
at the summit of Mount Ararat the plants of Lapland; a little lower,
those of Sweden; next, as he descended, those of Germany, France, and
Italy; and at the foot of the mountain, such as were natural to the
soil of Armenia. And the same has been observed of insects. Those
that inhabit the _plains_ of _northern_ regions have been found on
the _mountains_ of more _southern_ ones; as the beautiful and common
Swedish butterfly _Parnassius Apollo_, on the mountains of France,
and _Prionus depsarius_ on those of Switzerland[1479].
M. Latreille, having given a rapid survey of the peculiar
insect-productions of different countries, next attempts a division
of the globe into _climates_, which he thinks may be made to agree
with the present state of our knowledge, and be even applicable to
future discoveries. He proposes dividing it primarily into _Arctic_
and _Antarctic_ climates, according as they are situated _above_ or
_below_ the equinoctial line; and taking twelve degrees of latitude
for each climate, he subdivides the whole into _twelve_ climates.
Beginning at 84° N. L. he has _seven Arctic_ ones, which he names
_polar_, _subpolar_, _superior_, _intermediate_, _supratropical_,
_tropical_, and _equatorial_: but his _antarctic_ climates, as no
land has been discovered below 60° S. L., amount only to _five_,
beginning with the _equatorial_ and terminating with the _superior_.
He proposes further to divide his climates into _subclimates_,
by means of certain _meridian lines_; separating thus the _old_
world from the _new_, and subdividing the _former_ into two great
portions,--an _eastern_, beginning with _India_, and a _western_,
terminating with _Persia_. He proposes further that each climate
should be considered as having 24° of longitude, as well as 12°
of latitude[1480]. In this chart of insect Geography he states
that he has endeavoured to make his climates agree with the actual
distribution of insects[1481]; and it should seem that in many cases
such an agreement actually does take place: yet the division of the
globe into climates by _equivalent_ parallels and meridians, wears
the appearance of an artificial and arbitrary system, rather than of
one according with nature.
He has also pointed out another index to insect climates, borrowed from
the _Flora_ of a country. Southern forms in Entomology, he observes,
_commence_ where the _vine_ begins to prosper by the sole influence of
the mean temperature; that they are _dominant_ where the _olive_ is
cultivated; that species still _more_ southern are compatriots of the
_orange_ and _palmetto_; and that some _equatorial_ genera accompany
the _date_, the _sugar-cane_, the _indigo_ and _banana_[1482]. The idea
is very ingenious, and, under certain limitations, supplies a useful
and certain criterion. For though none of these plants are _universal_
in isothermal parallels of latitude; yet, as plants are more
conspicuous than insects, the Entomologist, furnished with an index
of this kind, may by it be directed in his researches for them; and
in all countries in which there is a material change of the climate,
as in France, there will be a proportional change in the _vegetable_
accompanied by one in the _insect_ productions.
ii. In considering the _range_ of insects I shall first advert to
that of _individual_ species. At the extreme limits of phanerogamous
vegetation we find a species of humble-bee (_Bombus arcticus_),
which, though it is not known to leave the Arctic circle, has a very
extensive range to the _westward_ of the meridian of Greenwich,
having been traced from Greenland to Melville Island; while to the
_eastward_ of that meridian it has not been met with. In Lapland
its place appears to be occupied by _B. alpinus_ and _lapponicus_,
with the former of which, though quite distinct, it was confounded
by O. Fabricius; but whether these range further _eastward_ of
that meridian has not been ascertained. From its being found in
the Lapland _Alps_[1483], it may be conjectured that _B. alpinus_
ranges as high on this side as _B. arcticus_ on the other, and may
perhaps be found in _Nova Zembla_. Some species that have been
taken in Arctic regions are not confined to them. Of this kind is
_Dytiscus marginalis_, which appears common in Greenland, abundant
in Britain, and is dispersed over all Europe; while _D. latissimus_
is more confined, neither ranging so far to the north or south;
and though found in Germany, not yet discovered in Britain. Other
species have a still more extensive range, and are common to the old
world and the new. Thus _Dermestes murinus_, _Brachinus crepitans_,
_Tetyra scarabæoides_[1484], _Pentatoma juniperina_, _Cercopis
spumaria_, _Vanessa Antiopa_, _Polyommatus Argiolus_, _Hesperia
Comma_, _Vespa vulgaris_, _Ophion luteus_, _Helophilus pendulus_,
_Oscinis Germinationis_, and many besides, though sometimes varying
slightly[1485], inhabit both Britain and Canada: and though vast
continents and oceans intervene between us, New Holland, and Japan;
yet all have some insect productions in common. With the former we
possess the painted-lady butterfly (_Cinthia Cardui_), with scarcely
a varying streak: and Thunberg, in his list of Japan insects, has
mentioned more than _forty_ species that are found also in this
country. Whether any species has a _universal_ range may be doubted,
unless indeed the flea and the louse may be excepted. On the other
hand, some are confined within very narrow limits. _Apion Ulicis_
for instance, abundant upon _Ulex europæus_ in Britain, has not, I
believe, been found upon that plant on the continent.
The geographical distribution of _groups_, is, however, far more
interesting than that of _individual species_: for in considering this
we see more evidently how certain _functions_ are devolved upon certain
_forms_, and can scan the great plan of PROVIDENCE, in the creation of
insects, more satisfactorily than by confining our attention to the
latter. Groups, according to their range, may be denominated either
_predominant_, _dominant_, _sub-dominant_, or _quiescent_.
1. M. Latreille has observed, that where the empire of _Flora_
ceases, there also terminates that of Zoology[1486]. _Phytiphagous_
animals can only exist where there are _plants_; and those that are
_carnivorous_ and feed upon the _former_, must of necessity stop
where they stop. Even the _gnat_, which extends its northern reign so
high[1487], must cease at this limit; while, where vegetation is the
richest and most abundant, there the animal productions, especially
the insect, must be equally abundant. I call that, therefore, a
_predominant_ group, members of which are found in all the countries
between these points, or from the limits of animal-depasturing
vegetation in the polar regions to the line.
Generally speaking, the _carnivorous_ insects, whether thalerophagous
or saprophagous, are of this description. _Calosoma_, which devours
Lepidopterous larvæ, though poor in species and individuals, is
widely scattered. Captain Frankland found _C. calidum_ in his Arctic
journey; _C. laterale_ and _curvipes_ inhabit tropical America[1488]:
_C. Chinense_, as its name indicates, is Chinese[1489]; Mr. MacLeay
has an undescribed species from New Holland; and _C. retusum_ was
taken in Terra del Fuego. Another genus, equally universal and richer
in numbers, is the lady-bird (_Coccinella_), which keeps within
due limits the _Aphides_ of every climate from pole to pole. The
_Libellulina_ pursue their prey both in Greenland and New Holland.
The _saprophagous_ carnivora are also similarly predominant;--the
_Silphidæ_, the _Dermestidæ_, the _Brachyptera_, the _Muscidæ_,
prey on carcases wherever the action of the solar beam causes them
to become putrid. Many of the above insects have probably their
_capital_ station, or that where the species are most numerous, in
or near the tropics; but the metropolis of the _Brachyptera_, at
least as far as we can judge from our present catalogues, is within
the temperate zone, particularly in Britain[1490]. The coprophagous
_Petalocera_ are most abundant in the hottest climates; but the
_Aphodiadæ_ form a predominant group: Professor Hooker took one
species in Iceland[1491], and it probably ascends higher; others
are found in India and China: but the metropolis of the group is
within the temperate zone. Perhaps no genus is more completely
universal than _Bombus_ (_Bremus_ Jur.), which, although its centre
or _metropolis_ is likewise in the northern temperate zone, extends
from Melville Island to the line. It is remarkable that some of
the tropical _Bombi_ wear the external aspect of _Xylocopæ_, the
kindred genus most prevalent in warm climates; and, _vice versâ_,
some _Xylocopæ_ resemble _Bombi_. I have a Brazilian undescribed
species of the latter genus, whose black body and violet-coloured
wings would almost cause it to be mistaken for a variety of _X.
violacea_; and _B. antiguensis_ and _caffrus_ F., (though their
aspect belies it,) which misled Fabricius, are true _Xylocopæ_. I
shall mention only one other predominant group, but that one of no
common celebrity, formed of the gnats, or genus _Culex_. These piping
pests, with their quiver--"venenatis gravida sagittis"--annoy man
almost from the pole to the line. What remarkably distinguishes them,
(as was formerly observed[1492],) and also the _Simulium_ or true
mosquito,--they appear to prevail most in the coldest and the hottest
climates, and the Laplander and the tropical American are equally
their prey; while the inhabitants of the temperate zone, with some
exceptions, suffer but little from them: so that they may be stated
to have both an _arctic_ and a _tropical_ metropolis.
2. There are other groups which, though their empire extends to the
tropics, fall short of the polar circles:--these I call _dominant_
groups. Of this description are some of the _Scarabæidæ_. _Onthophagus_
is found both in the old world and in the new, and in the temperate
and torrid zones. Its principal seat appears to be within the tropics,
but it may almost be said to have also a northern metropolis. More
than one species have been taken in New Holland. In general, tropical
insects exceed those of colder climates in _size_; but in the genus we
are speaking of, the _European_ species are usually larger than the
_Indian_. _Copris_ seems more abhorrent of cold than its near relation
_Onthophagus_. _C. lunaris_, which ranges northward as far as Sweden,
is the only recorded species found in Europe out of Spain. Latreille
says, that all the large species of this genus are equinoctial: but _C.
Tmolus_, described and figured by Fischer[1493], found in Asia near
Orenburg, north of 50° N. L., is as big as _C. Gigas_ or _bucephalus_.
Another dominant group of _Petalocera_, remarkable for the bulk and
arms of its tropical species, are the mighty _Dynastidæ_, the giants
and princes of the insect race. Though their metropolis is strictly
tropical, yet the scouts of their host have wandered even as far as
the south of Sweden, where one of them, _Oryctes nasicornis_, is
extremely common. _O. Grypus_[1494] and some other species are found
in South Europe; but though in a torpid state they can endure unhurt
the severity of a Scandinavian winter, they cannot when revived
stand the cold that often pinches Britons in the midst of summer,
and therefore are unknown in our islands[1495]. The _Sphæridiadæ_,
whose metropolis is within the northern temperate zone, extend from
thence beyond the line, since Dr. Horsfield found two species in
Java[1496]. It is probable, indeed, that this group is predominant.
Some dominant groups begin at a lower latitude. Of this description
are the carpenter-bees (_Xylocopa_), whose larvæ are preyed upon by
that of the _Horiadæ_[1497] under _two_ forms, which extend from the
tropics to about 50° N. L. Others are not common to both worlds. Thus,
while _Cantharis_ is the gift of PROVIDENCE to America as well as the
old world, _Mylabris_ is confined to the _latter_, where its range
is very extensive;--in Europe, from South Russia to Italy and Spain;
in Asia, from Siberia to India; and in Africa, from the shores of
the Mediterranean to the Cape of Good Hope; which last continent, to
judge from our present lists, especially the vicinity of the Cape,
may be called the metropolis of the group[1498]. On the other hand,
the _Rutelidæ_ and _Chlamys_, which have a range from Canada to the
tropics, (within which is their metropolis,) are purely _American_
groups. Many more might be named under this head, but these will
suffice for examples.
3. I call those _subdominant_ groups, which either never enter the
tropics, or those tropical ones whose range does not exceed 50° of
N. L. in the old world, or 43° in the new. I make this difference
because, as M. Latreille observes, the southern insects which in
Europe begin between 48° and 49° N. L., in America do not reach
43°.[1499] But though the winters in Canada, within the same parallel
as France, are longer and more severe than those even of Great
Britain or of Germany, yet the summers are intensely hot; so that
though tropical _species_ do not range so high, those of a tropical
_structure_, as Mr. W. S. MacLeay has intimated[1500], may be found
at a higher latitude in the new world than in Europe.
The genus _Melöe_ affords an instance of a subdominant group of the
first description. It ranges from Sweden to Spain and the shores
of the Mediterranean, and seems a tribe almost confined to Europe,
where it is not very unequally distributed. Of registered species
Britain possesses the largest proportion; but Mr. W. S. MacLeay is of
opinion that Spain is its true metropolis[1501]. I have a species of
this genus, taken in North America by Professor Peck. The splendid
genus _Carabus_ ranges still further north than _Melöe_[1502]. A
very fine species (_C. cribellatus_) inhabits the polar regions of
Siberia[1503]; but the metropolis of the group appears to be the
temperate zone: some, however, have been found in northern Africa;
and Sir Joseph Banks captured one in Terra del Fuego. Of those
whose range is between the tropics and 50° N. L. we may begin with
_Cicada_. One species, indeed, has been found by Mr. Bydder and
others, a little higher, near the New Forest, Hampshire. We may
take _Scolia_ for an example of a subdominant group beginning more
southward. Its species first appear about 43° N. L., and abound in
warm climates. In general most of those insects which M. Latreille
denominates _meridional_,--such as _Scarabæus_, _Onitis_, _Brentus_,
_Scarites_, _Mantis_, _Fulgora_, _Termes_, _Scorpio_, &c.--come under
the present head, and in fact all tropical forms that wander to any
distance within the above limits from their metropolis.
4. By _quiescent_ groups I mean those that have none, or no _high_
range as to latitude, from their centre or metropolis. I say as
to _latitude_, because these groups have often an extensive one as
to _longitude_. Thus, Mr. W. S. MacLeay has remarked to me, that
_Goliathus_ appears to belt the globe, but not under _one_ form. The
types of the genus are the vast African Goliaths (_G. giganteus_,
&c.), which, as well as _G. Polyphemus_, and another brought from
Java by Dr. Horsfield, have, like _Cetonia_[1504], the scapulars
interposed between the posterior angles of the prothorax and the
shoulders of the elytra[1505]: while the South American species
(_G. micans_, &c.) have not this projection of the scapulars; in
this resembling _Trichius_. Mr. MacLeay further observes, that the
female of the Javanese _Goliathus_ is exactly a _Cetonia_, while
that of the Brazilian is a _Trichius_. But quiescent groups have
not generally this ample longitudinal range. Thus, _Euglossa_, in
both its types,--one represented by _Eu. cordata_, and the other by
_Eu. surinamensis_,--is confined to the tropical regions of America.
_Doryphora_, likewise American, seems equally confined. _Asida_,
though a _southern_ genus, is not found to enter the _tropics_; and
_Manticora_ and _Pneumora_ are in nearly the same predicament.
Under the present head we may consider what may perhaps be denominated
without much impropriety _endemial_ groups; by which I mean those
groups that are regulated, as to their limits, not so much by the
temperature, or the northing and southing of the latitude, as by
the general aspect and circumstances of the country. Thus, the vast
and nearly insular continent of _Africa_, almost as wide as it is
long, and situated in or near the tropics, instead of inland seas or
sea-like rivers, is intersected by parched sandy deserts, extending
far and wide; circumstances which, though in the vicinity of its
streams it is humid, impart an unusual degree of _aridity_ as well
as heat to its general atmosphere; so that it well merits the poet's
epithet, _Leonum arida nutrix_; and is also peculiarly fitted for
all such animals, especially insects, as delight in a dry, sandy,
hot country, particularly such as are predaceous in their habits.
_America_, on the other hand, exhibits quite an opposite character.
It is long, and comparatively narrow; surrounded, and almost divided
into two continents, by immense circumfluent oceans; watered every
where by rivers and lakes that emulate seas: in some parts covered by
interminable forests; in others, intersected by ridges of the loftiest
mountains. These circumstances, except in its Llanos, Pampas, or
table-land, give a general character of humidity to its atmosphere,
and fit it particularly for the production of a vast variety of
peculiar plants, and for the residence of numerous and peculiar
phytiphagous insects and other animals[1506]. Midway between these two
continents lies a third (for so the vast island of New Holland may be
denominated), which presents new features in its general aspect, and
consequently new forms both in its _Flora_ and _Fauna_, mixed with many
old ones parallel to those both of the new world and the old. Perhaps
Europe and Asia, with several that are peculiar, agree more in their
animal productions than the continents just described.
Let us next particularize a few of the peculiar types that
distinguish particular continents and countries. The genera
_Manticora_, _Graphipterus_, _Glaphyrus_, _Eurychora_, _Pneumora_,
_Masaris_, and many others, are peculiar to Africa. In Asia
alone we find _Mimela_[1507], _Euchlora_[1508], _Colliuris_,
_Catascopus_[1509], _Apogonia_[1510], a peculiar type of _Horia_,
&c. In America, _Agra_, _Galerita_, _Nilio_, another type of
_Horia_, _Tetraonyx_, _Rutela_, _Doryphora_, _Alurnus_, _Erotylus_,
_Scotinus_[1511], _Cupes_, _Corydalis_, _Labidus_, _Heliconius_,
_Castnia_, &c. And in New Holland, _Helluo_, _Elephastomus_,
_Anoplognathus_, _Diphucephala_[1512], _Cerapterus_, _Heleus_,
_Adelium_, _Notoclea_, _Achilus_, _Thynnus_, _Nycterobius_, &c.
The countries bordering upon the Mediterranean, the Black, and the
Caspian seas, agree in producing similar insects. These countries, and
the Cape of Good Hope though so distant from them, appear to be the
principal seat of Heteromerous _Coleoptera_, of the genera _Lixus_ and
_Brachycerus_, and of the conical _Buprestes_[1513]. But the insects of
Guiana, on one side the Cordilleras, differ from those of New Granada
and Peru on the other; and similar differences are observed in other
_neighbouring_ countries separated by natural boundaries.
iii. Another head connected with the topographical distribution of
insects relates to their _representation_ of each other. Here we
may observe, that some insects represent each other only in their
_form_; others also in their _function_; and others in _both_. I
shall give some instances of each. In Brazil there is a group of
petalocerous beetles (_Chasmodia_), one of the _Rutelidæ_, which
in New Holland has a representative, as to _form_, in one of the
_Cetoniadæ_ (_Schizorhina_[1514]), which, having soft mandibles, must
have a different function:--it is to be observed, however, that these
insects appear to approach each other in the series of affinities.
Again, the _Carabidæ_ may in the same country be said to have a
representative in the remarkable heteromerous genus _Adelium_[1515],
which is altogether an analogy. Others are representative only in
their _function_. The general function of insects is to remove
_nuisances_ and to check _redundances_,--the saprophagous tribes do
the one, and the thalerophagous the other. In going from the poles
to the line,--in proportion as the heat increases, the quantum of
work of both kinds increases; and new forms are either added to
the old ones, so as to increase their momentum; or new ones, more
powerfully talented, replace the old ones, and act in their stead:
thus we see a gradual and interesting change take place in proportion
as we approach the maximum of heat and of insect population. At the
Cape, the _universal Cicindelæ_ are aided by _Manticora_; in North
America, the _Silphidæ_ by a new group, the type of which is _Silpha
Americana_ (_Necrophila_, K.MS.); in South America, _Copris_ by
_Phanæus_. Again: _Colliuris_ and _Drypta_ of the _old_ world, in
the _new_ give place to _Ctenostoma_ and _Agra_. The honey and wax
of Europe, Asia, and Africa, is prepared by _bees_ congenerous with
our common hive-bee (_Apis_); while in America this genus is not
found as a native, but is replaced by _Melipona_ and _Trigona_[1516];
and in New Holland by a still different but undescribed type. The
_Melolonthidæ_ and _Rutelidæ_ of the old and new world appear to
have their work done in that country by the brilliant and numerous
_Anoplognathidæ_. The _Rhipicera_ of Brazil is of a different type
from that of New Holland. The singular genus _Cremastocheilus_ of
North America has its representative in Africa in _Genuchus_[1517].
The _Lucani_ of the rest of the world give place in New Holland to
_Lamprima_ and _Ryssonotus_.--I could produce a much greater number
of examples, but these are sufficient to explain my meaning.
* * * * *
Having thus given you some, though an imperfect account, of the
_geographical_ distribution of insects, I am next to say something
concerning their _local_ distribution in any district, or their
favourite _haunts_; a knowledge of which, with respect to those of
our own country, is indispensable to the collector.
The surface of a country consists either of mountains, hills and
valleys, or of plains. It is diversified by forest, wood, or copse;
and watered by rivers, rivulets, lakes, and pools. Those parts that
are not clothed with wood are either open or inclosed, forming
grassy downs, heaths, pastures, meadows, morasses, and arable land.
The soil also is equally various:--we find clay, loam, marl, chalk,
vegetable mould, moor, sand, &c. The mountains and hills are either
covered with a stratum of soil, or are rocky and bare; the arable
lands are divided by living or dead fences, the latter formed of
various materials,--or else they are open, and the property only
marked out by grassy balks, &c. All these places abound in shrubs and
plants; some local, and some generally distributed. But besides the
_land_ and its _fresh_ waters, we must look also to the _sea_, and
its sandy, pebbly, or rocky shores, and the sea-wrack that is cast
up upon them; the _estuaries_ that receive its tides; the brackish
waters and saline marshes in its vicinity. All the above places, when
opportunity serves, the Entomologist should explore, for in almost
all he will find peculiar kinds of insects.