or tract.
[1413] Συνιστημι, To stand together.
[1414] Πιεζω, To press.
[1415] Οδους, A tooth.
[1416] Μιτος, A thread.
[1417] _Unogata_ is probably a mistake for _Onychata_; from Ονυξ, A
claw.
[1418] Doubtless for _Polygnatha_; from Πολυς, Many, and Γναθος, A jaw.
[1419] Κλειστος, Closed, and Γναθος.
[1420] Εξω, Without, and Γναθος.
[1421] Γλώσσα, A tongue.
[1422] Ῥυγχος, A rostrum.
[1423] Αντλια, A pump.
[1424] Dispositio insectorum sistit divisiones s. conjunctiones
eorum, et est _artificialis_ quæ _Classes_ et _Ordines_, et
_naturalis_ quæ _genera_, _species_, et _varietates_ docet. _Philos.
Entomol._ vi. §. 2.
[1425] _Ibid._ §. 7.
[1426] Latreille _Gen. Crust. et Ins._ iii. 214.
[1427] With respect to Natural Genera he says--"Cavendum tamen ne nimis
imitando _naturam_ systematis amittamus filum Ariadneum." _Ibid._ § 6.
[1428] Fab. _Entomolog. Syst. em. et auct._ i. Præf. iv.
[1429] Fabricius calls this a chaos, and threatens to prove it, but
he never fulfilled his threat. See Fab. _Supplem._ Præf. i.
[1430] _Introd. ad Hist. Nat._ 401.
[1431] See _N. Dict. d'Hist. Nat._ x. article _Entomologie_; and
_Familles Naturelles du Règne Animal_ 262--.
[1432] These tables, except the first, are taken from the _Familles
Naturelles du Règne Animal_. As a new edition of M. Le Baron Cuvier's
_Règne Animal_ is preparing, M. Latreille will doubtless give in it a
still more improved arrangement of the _Crustacea_, _Arachnida_, and
_Insecta_.
[1433] Several of the minor groups given in the table he has further
resolved before he arrives at his genera.
[1434] VOL. III. p. 348, note^c.
[1435] See above, p. 433.
[1436] _Syst. des Anim. sans Vertèbr._ 185.
[1437] _Ibid._ 171.
[1438] _Anim. sans Vertèbr._ iii. 332--.
[1439] _Anat. Comp._ i. _t._ viii.
[1440] _Expos. d'une Meth. Nat._ 17.
[1441] VOL. III. p. 19.
[1442] _Linn. Trans._ xi. 376. N. B. I have transferred from the
_Arachnida_ his suborder _Notostomata_, as he subsequently placed it
at the end of _Insecta_, under the _Omaloptera_.
[1443] See above, pp. 378, 380, 385, 390.
[1444] VOL. III. p. 14.
[1445] See VOL. III. p. 25--. and above, p. 394--.
[1446] _Hor. Entomolog._ _c._ vi.
[1447] See above, p. 382.
[1448] _Hor. Entomolog._ 420--.
[1449] _Ibid._ 422.
[1450] Other systems or methods have been promulgated by various
authors, as by Schæffer, Scopoli, Geoffroy, &c. Walckenaer and
Blainville have proposed one founded on the number of the _legs_ of
insects; but those in the text are the principal and best known.--_N.
Dict. d'Hist. Nat._ xvi. 277.
[1451] _Linn. Trans._ xiv. 59--. _Annulos. Javan._ 6. See above, p. 408.
[1452] Latreille _Gen. Crust. et Ins._ iii. 226. note 1.
[1453] _Præf._ ii.
[1454] _Linn. Trans._ ii. 63--.
[1455] _Mon. Ap. Angl._ i. 211--.
[1456] VOL. III. p. 620. n. 3.
[1457] It may not be unprofitable here to mention those works which
the Entomologist may find it most useful to consult in various
departments of the science. For descriptions of the _Genera_ and
_Species_ of insects in general, he must have recourse to the
_Entomologia Systematica emendata et aucta_ of Fabricius, and its
_Supplement_; to the volumes he subsequently published under the
titles _Systema Eleutheratorum_, _Rhyngotorum_, _Glossatorum_,
_Piezatorum_, and _Antliatorum_; to the _Genera Crustaceorum et
Insectorum_ of Latreille; to the same department of the _Règne
Animal_ of Cuvier; and to the _Animaux sans Vertèbres_ of Lamarck.
He will find the genera of Linné and Fabricius illustrated by
_figures_, in Rœmer's _Genera_; and many of the species described
by the latter in Coquebert's _Illustratio Iconographica_. In our
countryman Drury's beautiful _Illustrations of Natural History_,
a large number of new and rare insects are depicted; and in Mr.
Donovan's _Insects of China, India, and New Holland_, some of the
most brilliant and interesting that have been imported from those
countries. Panzer's _Faunæ Insectorum Germanicæ Initia_ has little
short of 3000 figures of insects of every Order (a considerable
number of which are found to inhabit Britain), by the celebrated
Sturm; and the latter, in his _Deutschlands Fauna_, has illustrated
many Coleopterous genera analytically (as has also M. Clairville the
weevils and Predaceous beetles of Switzerland in his _Entomologie
Helvétique_) by his admirable pencil. Beetles in general are well
figured and described in Olivier's splendid _Entomologie_; as are
those of Europe in a beautiful work now in course of publication,
under the title of _Coleoptères d'Europe_, by MM. Latreille and
Dejean. The latter author has also begun a work on this Order under
the title of _Species général des Coléoptères de la Collection de
M. Le Comte Dejean_; two volumes of which have appeared, containing
part of the _Carabici_ Latr. but I fear it has stopped for want of
encouragement. Had the descriptions been less verbose it would have
had a better chance of success. For the _Orthoptera_ and _Hemiptera_,
the student must have recourse to Stoll's _Spectres_, _Mantes_,
_Sauterelles_, _Grillons_, _Blattes_, _Cigales_, and _Punaises_. To
a knowledge of the species of _Lepidoptera_, the admirable figures
of Cramer (_Papillons Exotiques de trois Parties_ _du Monde_), Esper
(_Schmetterlinge_, _Tagschmetterlinge_), Hübner (_Schmetterlinge_,
&c.), and Ochsenheimer's valuable _Schmetterlinge von Europa_, with
the continuation by Treitschke, will afford a useful avenue. Meigen
also, author of a most valuable work on the Europæan _Diptera_, is
publishing at this time a work on _Lepidoptera_ under the title
of _Europäische Schmetterlinge_. To the _Hymenoptera_ Jurine and
Christian are the best guides, and to the _Diptera_ Meigen.
With regard to works in British Entomology in general--Donovan's
_Natural History of British Insects_, and Samouelle's _Entomologist's
Useful Compendium_, will be found very excellent helps to the
student. For the British Genera, the most important work that has
yet appeared is Mr. John Curtis's _British Entomology_, in which
not only are the insects admirably represented, but their trophi
correctly delineated, accompanied by able descriptions. For the
_Coleoptera_ of our country, Mr. Marsham's _Entomologia Britannica_
should be consulted: for the _Lepidoptera_, the _Butterflies_ of
Lewin, Mr. Haworth's useful _Lepidoptera Britannica_, and Miss
Jermyn's _Butterfly-Collector's Vade Mecum_; and for the English
species of Linné's genus _Apis_, the _Monographia Apum Angliæ_. A
British _Fauna Insectorum_, under the title of _Illustrations of
British Entomology_, has at length been happily begun by a gentleman
(J. F. Stephens, Esq.) who both by his accurate knowledge of the
subject, and the extent of his collection of British Insects, is best
qualified to undertake it. As far as it has proceeded, it is ably
executed, and possesses this advantage, (an advantage seldom to be
obtained in works published periodically,) that it finishes, as far
as possible, as it goes.
LETTER XLIX.
_GEOGRAPHICAL DISTRIBUTION OF INSECTS;
THEIR STATIONS AND HAUNTS;
SEASONS; TIMES OF ACTION AND REPOSE._
Though no subject is more worthy of the attention of the Entomologist
than the _Geographical Distribution_ of insects, yet perhaps there
is none connected with the science, for the elucidation of which he
is furnished with fewer materials. The geographer of these animals
sitting by his fireside, even supposing his museum as amply stored as
that of Mr. MacLeay, and the _habitats_ of its contents as accurately
indicated, still labours under difficulties that are almost
insuperable; so that it is next to impossible, with our present
knowledge of the subject, to give _satisfactory_ information upon
_every_ point which it includes. Had he the talents and opportunities
of a Humboldt, and could, like him, traverse a large portion of the
globe, he would endeavour to note the elevation, the soil and aspect,
the latitude and longitude, the mean temperature and meteorological
phænomena, the season of the year, the kind of country, and other
localities connected with the insects he captured, and so might build
his superstructure upon a sure basis. But these are things seldom
registered by travellers that take the trouble to collect insects;
who, if they specify generally the country in which any individual
was found, think they have done enough. But to say that an insect was
taken in India, China, New Holland, and North or South America,--when
we consider the vast extent of those regions,--is saying little of
what one wishes to know even with respect to its _habitat_. You must
regard therefore, after all, what I have been able to collect,--and
for which I am greatly indebted to the labours of my few but able
precursors in this walk,--as merely approximations to an _outline_,
rather than as a correct _map_ of insect Geography.
Amongst the numerous obligations that he conferred upon Natural
History, Linné was the first Naturalist who turned his attention to
the _Geographical Distribution_ of its objects, especially that of
the _Vegetable_ Kingdom[1458]: and the accomplished traveller Baron
Humboldt, by the observations he made on this subject in the course
of his peregrinations in tropical America, has furnished the Botanist
with a clue which, duly followed, will enable him to perfect that
part of his science; an end to which the learned observations of
Messrs. R. Brown and Decandolle have greatly contributed[1459]. With
regard to _animals_, Mr. White, so long ago as 1773, had observed
that they, as well as plants, might with propriety be arranged
geographically[1460]: and in 1778 Fabricius in his _Philosophia
Entomologica_ applied the principle to _insects_[1461]. Nearly forty
years elapsed before any improvement or enlargement of this last
department was attempted; when in 1815 M. Latreille, stimulated
by what had been effected in Botany, in a learned and admirable
memoir[1462] endeavoured to place Entomology in this respect by
the side of her more fortunate sister: and subsequently Mr. W. S.
MacLeay, in the memorable work so often quoted in our correspondence,
has viewed the subject in another light, and added some important
information to what had been before collected[1463].
The point now under consideration naturally divides itself into two
principal branches;--the _numerical_ distribution of insects, and the
_topographical_.
I. By the _numerical_ distribution of insects I mean not only the
number which PROVIDENCE has employed to carry on its great plan on
this terraqueous globe, or any given portion of it; or of the species
of which each group or genus may be supposed to consist; or of the
comparative number of individuals furnished by each species,--points
of no easy solution: but more particularly their distribution
according to their _functions_, whether they prey upon _animal_ or
_vegetable_ matter, and in its _living_ or _decaying_ state.
We have no data enabling us to ascertain with any degree of accuracy
the actual _number_ of species of insects and _Arachnida_ distributed
over the surface of the globe; but it is doubtless regulated in a
great degree by that of plants. We should first then endeavour to
gain some just though general notion on that head. Now Decandolle
conjectures that the number of the species of plants, 60,000 being
already known, may be somewhere between 110,000 and 120,000[1464].
If we consider with reference to this calculation, that though the
great body of the mosses, lichens, and sea-weeds are exempt from the
attack of insects, yet as a vast number of phanerogamous plants and
fungi are inhabited by _several_ species, we may form some idea how
immense must be the number of existing insects; and how beggarly
does Ray's conjecture of 20,000 species[1465], which in his time
was reckoned a magnificent idea, appear in comparison! Perhaps
we may obtain some approximation by comparing the number of the
species of insects already discovered in _Britain_ with that of its
_phanerogamous_ plants. The latter,--and it is not to be expected
that any large number of species have escaped the researches of
our numerous Botanists,--may be stated in round numbers at 1500,
while the British insects, (and _thousands_ it is probable remain
still undiscovered,) amount to 10,000; which is more than _six_
insects to _one_ plant. Now though this proportion, it is probable,
does not hold universally; yet if it be considered how much more
prolific in species tropical regions are than our chilly climate,
it may perhaps be regarded as not very wide of a fair medium. If
then we reckon the phanerogamous vegetables of the globe in round
numbers at 100,000 species, the number of insects would amount to
600,000. If we say 400,000, we shall perhaps not be very wide of the
truth. When we reflect how much greater attention has been paid to
the collection of plants than to that of insects, and that 100,000
species of the latter may be supposed already to have a place in our
cabinets[1466], we may very reasonably infer that at least _three
fourths_ of the existing species remain undiscovered.
Certain groups and genera are found to contain many more species
than others: for instance, the _Coleoptera_ and _Lepidoptera_ Orders
than the _Orthoptera_ and _Neuroptera_; the _Rhincophora_ than the
_Xylophagi_: the _Dytiscidæ_ than the _Gyrinidæ_; _Aphodius_ than
_Geotrupes_; _Carabus_ than _Calosoma_. Again, some insects are
much more prolific than others. Thus the _Diptera_ Order, though
not half so numerous with respect to _species_ as the _Coleoptera_,
exceeds it greatly in the number of _individuals_, filling the air
in every place and almost at every season with its dancing myriads.
We rarely meet with a single individual of the most common species
of _Calosoma_ or _Buprestis_; whilst the formicary, the termitary,
the vespiary, and the bee-hive send forth their thousands and tens
of thousands; and whole countries are covered and devastated by the
_Aphides_ and the Locusts. An all-wise PROVIDENCE has proportioned
the numbers of each group and species to the work assigned to them.
And this is the view in which the numerical distribution of insects
is most interesting and important: and we are indebted to Mr. W. S.
MacLeay for calling the attention of Entomologists more particularly
to this part of our present subject.
With regard to their _functions_, insects may be primarily divided
into those that feed upon _animal_ matter and those that feed upon
_vegetable_. At first you would be inclined to suppose that the
_latter_ must greatly exceed the _former_ in number: but when
you reflect that not only a very large proportion of Vertebrate
animals, and even some _Mollusca_[1467], have more than _one_ species
that preys upon them, but that probably the majority of insects,
particularly the almost innumerable species of _Lepidoptera_,
are infested by parasites of their own class, sometimes having a
different one appropriated to them in each of their preparatory
states[1468], and moreover that a large number of beetles and
other insects devour both living and dead animals,--you will begin
to suspect that these two tribes may be more near a counterpoise
than at first seemed probable. In fact, out of a list of more than
8000 British insects and _Arachnida_ taken several years ago, and
furnished chiefly by Mr. Stephens, I found that 3894 might be called
carnivorous, and 3724 phytiphagous[1469]; so that, speaking roundly,
they might be denominated equiponderant.
Carnivorous and phytiphagous insects may be further subdivided
according to the _state_ in which they take their _food_,--whether
they attack it while _living_, or not till after it is _dead_. To
adopt Mr. W. S. MacLeay's phraseology, the former may be denominated
_thalerophagous_, and the latter _saprophagous_. The British
saprophagous _carnivorous_ insects, compared with those that are
thalerophagous, are about as 1:6; while the phytiphagous ones are
as 1:9. The _thalerophaga_ in both tribes may be further subdivided
as they take their food by _suction_ or _mastication_: in the
_carnivorous_ ones, the suckers to the masticators in Britain are
nearly as 1:6; but with respect to the _phytiphagous_ tribe you
must take into consideration that some insects imbibing their food
by _suction_ in their _perfect_ state (as the great body of the
_Lepidoptera_), _masticate_ it when they are _larvæ_: deducting
therefore from both sides the insects thus circumstanced, the
masticators will form about _three fourths_ of the remaining British
thalerophagous insects. Another circumstance belonging to this
head must not be passed without notice:--there are certain insects
feeding upon liquid food that do not _suck_, but _lap_ it. This is
the case with the _Hymenoptera_, who, though they are mandibulate,
generally lap their food (the nectar of flowers) with their tongue,
and may be called _lambent_ insects: nor is this practice confined
to that order, but all the mandibulate insects that feed on that
substance merit the same appellation. The absorption of this nectar
is so important a point in the economy of nature, that a very large
proportion of the insect population of the globe in their perfect
state, are devoted to it. Considerably more than half the species
indigenous to Britain fulfill this function, and probably in tropical
countries the proportion may be still larger.
To push this analysis still further--Amongst our carnivorous
thalerophaga, _aphidivorous_ insects are about as 1:14; and amongst
the phytiphagous, the _fungivorous_ ones form about a _twentieth_;
and the _granivorous_ about a _twenty-fifth_ part of the whole.
Again: in the _saprophaga_ the _lignivorous_ tribes form more than
_half_, and the _coprophagous_ ones more than a _third_.
If you wish to know further the relative proportions of the different
_Orders_ to each other--The _Coleoptera_ may be stated as forming
at least 1:2 of our intire insect population; the _Orthoptera_ and
_Dermaptera_ as about 1:160; the _Hemiptera_ as 1:15; the _Lepidoptera_
as more than 1:4; the _Neuroptera_ with the _Trichoptera_ as 1:29; the
_Hymenoptera_ as about 1:4; the _Diptera_ as not 1:7; and the _Aptera_
and _Arachnida_ as perhaps amounting to 1:19[1470].
To extend this inquiry to _exotic_ and more particularly to
_extra-European_ insects, in the present state of our knowledge,
would lead to no very satisfactory results. The lists we have are
so imperfect, that those which tell most in this country,--I mean
the more minute insects and the _Brachyptera_--have hitherto formed
a very small, if any part, of the collections made _out_ of Europe.
Mr. W. S. MacLeay however, who, besides his father's (particularly
rich in _Petalocera_), has had an opportunity of examining the
Parisian and other cabinets, finds that the species of _coprophagous_
insects _within_ the tropics, to those _without_, are nearly in the
proportion of 4:3; and that the coprophagous _Petalocera_, to the
remainder of the saprophagous ones, may be represented by 3:2[1471].
It may be inferred, from the superabundance of plants and animals
in equinoctial countries, that the number of species of insects in
general is greater within than without the tropics: the additional
momentum produced by the vast size of many of the tropical species
must also be taken into consideration.
II. There are three principal points that call for attention under
the _second_ branch of our present subject--the _topographical_
distribution of insects; namely, their _Climates_, their _Range_, and
their _Representation_.