Part 35

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.

As _mountains_ and _hills_ have usually their own Flora, the insects appropriated to alpine plants can only be met with where the pabulum is found. Here also those northern insects that are impatient of a warmer climate will take their station, if they migrate to the southward[1518]. The predaceous beetles likewise sometimes frequent a mountainous district. _Carabus glabratus_ was first taken by Professor Hooker on Ingleborough; and probably, if the Welsh and Scotch mountains were duly investigated by an Entomologist, many novelties would reward his toils. The _valleys_ and _plains_, especially those of a sunny exposition, abound in insects. When the heat of the atmosphere indisposes you for motion, you will find it no unprofitable or unpleasant employment, lying on the grass, to search for minute beetles, which you will there find coursing about amongst the tufts and roots of the herbage. Thus you may procure many of the _Pselaphidæ_, which you would not otherwise meet with. Even when the grass is grown up, insects are fond of alighting upon its spikes, and thence drop or run to the ground. Should circumstances ever carry you abroad to the steppes or grassy plains of Tartary, or to Hungary, you would find there two or three species of the singular genus _Lethrus_, which burrows in the soil. Every hole is inhabited by a male and female;--from it they issue to attack the plants or vines; and having cut out the heart of a plant, go backwards like a crab with the prize to their burrow. At the time of pairing, sometimes violent battles, encouraged by the female, take place between the male and a stranger of that sex desirous of admission, which cease only with the death or flight of the stranger[1519]. The vicinity and borders of _woods_ generally abound in insects of every Order; and if you proceed, as hereafter directed, will furnish you with numerous prizes, especially of _Lepidoptera_. Here alone you can meet with the purple emperor butterfly (_Apatura Iris_); and if properly equipped you may readily secure him.

The _waters_ you will find nearly as prolific in insects as the land. In them, amongst the beetles, you may expect to meet with _Dytiscus_, _Haliplus_, _Pælobius_, _Hyphydrus_, _Hydroporus_, _Noterus_, _Colymbetes_, and other _Dytiscidæ_; the _Gyrini_, _Hydrophili_, _Hydrænæ_, _Elophori_, &c.: under stones, the _Elmis_; and in the mud, the _Parni_ and _Heteroceri_. Some _Sphæridiadæ_ are also aquatic: I have taken more than once _Cercyon hæmorrhoidale_ from the under side of a piece of wood immersed in a canal[1520]. Even a few of the weevil tribes are to be met with in water. _Lixus paraplecticus_, _Tanysphyrus Lemnæ_, _Bagous atrirostris_, are of this description. A species of _Ceutorhynchus_ of Germar's _third_ family (_C. Natator_ K.) _swims_ well. On aquatic plants you must look for _Helodes_ and the splendid _Donaciæ_, which, living on submerged shoots and roots of these plants in their larva state, continue to attend them when perfect. Amongst the _Eutrech_in_a_[1521],--_Elaphrus_, _Notiophilus_, and _Bembidium_ frequent humid places, as the banks of rivers and ponds; and in such a station, under the roots of _Potentilla anserina_, _Polygonum_, &c. if you should be fortunate enough to find _Omophron limbatum_, which connects the _Eutrech_in_a_ with the _Eunech_in_a_, you will make a valuable addition to the list of British insects. In the waters also you will meet with many Heteropterous _Hemiptera_; as _Gerris_, _Hydrometra_, and _Velia_, and all the _Hydrocorisæ_ or water-bugs. On aquatic plants the larvæ of some _Lepidoptera_ feed, as _Hydrocampa stratiotata_, _potamogata_, &c. Those also of the _Trichoptera_ must be sought for in the water: and if you should feel inclined to see an interesting collection of their very curious _cases_, Mr. Sheppard of Wrabness can gratify your curiosity. Though few or no _Hymenoptera_ frequent this element, vast numbers of _Diptera_ are there alone to be met with in their preparatory state,

## particularly the gnats. We learn from Humboldt a curious fact with