first very slight, and require a practised eye to catch them, yet
it occasionally happens that considerable apparent differences
may safely be disregarded. The _colour_ of insects,--to which
unhappily for want of better characters we are so generally forced
to have recourse,--though usually constant, is in some species very
variable[1589]. This is the case sometimes with _whole_ colours.
Thus _Carabus arvensis_, _Pœcilus cupreus_, &c., are sometimes of a
copper colour; at others, resemble brass; at others, they are green
or blue, and even black. The colour of _spots_ also often varies.
In some individuals of _Pentatoma oleracea_ they are pale, and in
others red. The number and shape of spots are also often inconstant.
Many of the species of _Coccinella_ so abound in these variations,
that nothing short of the most careful examination can enable you
to distinguish the species from the variety. Insects vary also in
_size_: but as this is never assumed as a specific character, it will
not occasion you much trouble. Where the difference in this respect
between two specimens is very great, the presumption is that they are
specifically distinct. Differences in _sculpture_ and _proportion_
do not always indicate different _species_; this being sometimes, as
we have seen above, only a _sexual_ character[1590]. Authors also
in their descriptions, in this respect sometimes mislead the young
student. When Linné calls the _thorax_ of _Aphodius erraticus_ smooth
(_lævis_) he would not expect to find it covered with impressed
puncta, and with a longitudinal posterior impressed line. Likewise
in describing _Chlænius vestitus_ and _nigricornis_, Fabricius
passes without notice their punctate surface, so different from that
of other _Harpalidæ_. Errors of this kind however, it is but fair
to observe, are chiefly to be attributed to the circumstance that
both Linné and Fabricius rarely employed a _microscope_ in making
descriptions; though no one now attempts this, except where insects
are large, without such an aid.
If you ask, How am I to acquire this delicacy of tact which is to
decide when the terms of a specific character are to be rigidly
adhered to, and when taken with a certain latitude? I answer, In the
same way in which a connoisseur attains the faculty of discerning
the works of different masters in painting;--by such careful study
of your author as will make you master of his style. Thus you will
soon perceive in what cases expressions are to be taken literally and
strictly, or with some allowance and abatement.
There yet remains more distinctly to be adverted to, the assistance
that may be derived in the investigation of insects from _figures_.
Generally speaking, these should never be referred to in the first
instance, but be regarded as a resource when the ordinary methods leave
the subject of inquiry doubtful. Those who begin their entomological
studies by turning over figures usually end them there, and never
attain to that nameless tact in making out insects that can only
be the result of patient study. Indeed figures, though often very
useful, and sometimes indispensable, can scarcely ever exhibit those
nice characters, particularly as to sculpture, that distinguish some
insects. Our modern artists, indeed, are remedying this defect of the
art, by giving in many cases the thorax or elytrum apart, with all its
sculptural peculiarities: but this is not, and cannot be, done so as
to represent every one. But though in general figures should be your
last resort, I know not whether an exception to the rule may not be
advisable with respect to the _Lepidoptera_, which are more difficult
to be intelligibly described than any other order of insects; while a
good figure exhibits to the eye all those markings and shades, that
scarcely any description can place clearly before the mind.
When every attempt to investigate the name of your unknown species
fails, and you have consequently reason to believe that it is
undescribed, the best mode you can pursue for retaining that knowledge
of its characters, which from your long investigation you must have
acquired, is to note them down in your _entomological journal_,
inserting it under its proper genus with a trivial name of your own.
Such a journal you will find almost a _sine qua non_ for containing a
catalogue of your insects, and to register any observations concerning
individuals you may have had an opportunity of making. With regard to
this journal, I should recommend to you to get two blank books. One a
duodecimo of 200 or 300 pages, to contain the mere catalogue of your
insects, their habitat and localities, or the source from which you
derived them. In this you should number the genera in Roman capitals,
and the species under each by a figure; leaving considerable space
at the end of each genus for the insertion of new species. The other
book should be of an octavo size, containing 400 or 500 pages. Under
the number of each genus and species you might describe and figure
it, if undescribed; if described, note in what it varies from the
description, and what characters are overlooked: and in general, insert
such observations, with regard to its economy and habits, as you may
have had an opportunity of making.--As to foreign insects, wherever you
can, upon _good_ authority, be particular in indicating the country and
station of each specimen.
I need not say much to you concerning the microscopes you should use
for the examination of insects, a common pocket one of three glasses
of different powers will answer every ordinary purpose[1591].
* * * * *
We have treated hitherto of insects as we find them now inhabiting
our globe: but I must not conclude our correspondence without taking
some notice of those that are found in a _fossil_ state. Fossil
insects may be divided into those that are found in _amber_, and
those that are found in _other_ substances.
It has been observed with respect to insectiferous amber, that the
greater part of the insects found in it exist no longer in the
countries that produce that amber, and that in every different
locality the insects found in it are different. Thus the amber
of Sicily contains various species of _Coleoptera_ not to be met
with in other ambers, while that of the Baltic is rich in _Diptera_
and _Neuroptera_[1592]. It is further observed, that the insects
inclosed in the amber of Prussia, and those figured by Sendelius in
his _Historia Succinorum_, all belong to genera at this time found
in Europe[1593]. Insects of the following genera are recorded as
having been found in this singular substance: _Platypus_, _Elater_,
_Atractocerus_; _Gryllus_, _Mantis_; larvæ of _Lepidoptera_;
_Trichoptera_; _Ephemera_, _Perla_, _Termes_; _Formica_; _Tipula_,
_Bibio_, _Empis_; _Scolopendra_; and various _Arachnida_[1594].
In a piece of amber in my collection I find _Evania_, _Formica_,
_Chironomus_, and some _Arachnida_.
Fossil insects have also been found in other substances. Parkinson
figures larvæ of _Libellulina_ found in limestone[1595]; some
_Melolonthæ_ in slate; a _Polistes_ in schistus; _Carabi_ and
_Necrobia_ in vegetable debris: but some of these rather belong to a
comparatively modern formation[1596].
* * * * *
I observed in the outset of our correspondence, that we were entering
an august temple, exhibiting in its inmost sanctuary the symbols of
the Divine Presence[1597]. In proportion as we have penetrated, glory
from that Shechinah has more and more shone forth: and whether we
have considered the uses of insects, their ways and instincts, their
forms and structure, and their arrangement in a wondrous and complex
system, the WISDOM, POWER and GOODNESS of their and our CREATOR have
every where been marvellously conspicuous, and calculated to awaken
in us every devotional feeling. If, indeed, we admire and study
these little creatures, or any other department of nature, without
reference to their CREATOR, and collect and love them merely for
_themselves_, we shall be in some sense idolaters, and, like the
ancient world, put the _works_ of GOD in his place. But if, while
we admire them and store them up and study them, we see in them his
glory reflected, and in the _creature_ love the CREATOR, the study of
them, in conjunction with that of the written Word, will be highly
beneficial to us, and at the same time that it ministers to our
temporal enjoyment will promote our eternal interests.
Taking this view, I cannot better close our correspondence on the
subject that has so long occupied us, than in the pious words of one
of our most admired poets:
"Happy if full of days--but happier far,
If, ere we yet discern life's evening star,
Sick of the service of a world that feeds
Its patient drudges with dry chaff and weeds,
We can escape from custom's idiot sway,
To serve the Sovereign we were born t' obey.
Then sweet to muse upon his skill display'd
(Infinite skill) in all that he has made!
To trace, in Nature's most minute design,
The signature and stamp of pow'r divine,
Contrivance intricate, express'd with ease,
Where unassisted sight no beauty sees,
The shapely limb and lubricated joint,
Within the small dimensions of a point,
Muscle and nerve miraculously spun,
His mighty work, who speaks and it is done,
Th' Invisible in things scarce seen reveal'd,
To whom an atom is an ample field:
To wonder at a thousand insect forms,
These hatch'd, and those resuscitated worms,
New life ordain'd and brighter scenes to share,
Once prone on earth, now buoyant upon air,
Whose shape would make them, had they bulk and size,
More hideous foes than fancy can devise;
With helmet-heads and dragon-scales adorn'd,
The mighty myriads, now securely scorn'd,
Would mock the majesty of man's high birth,
Despise his bulwarks, and unpeople earth:
Then with a glance of fancy to survey,
Far as the faculty can stretch away,
Ten thousand rivers pour'd at his command
From urns that never fail through every land;
These like a deluge with impetuous force,
Those winding modestly a silent course;
The cloud-surmounting alps, the fruitful vales;
Seas on which every nation spreads her sails;
The sun, a world whence other worlds drink light;
The crescent moon, the diadem of night;
Stars countless, each in his appointed place,
Fast anchor'd in the deep abyss of space:--
At such a sight to catch the poet's flame,
And with a rapture like his own exclaim,
These are thy glorious works, thou source of good!
How dimly seen, how faintly understood!
Thine, and upheld by thy paternal care,
This universal frame, thus wondrous fair;
Thy power divine, and bounty beyond thought,
Adored and praised in all that thou hast wrought.
Absorb'd in that immensity I see,
I shrink abas'd, and yet aspire to thee;
Instruct me, guide me to that heavenly day,
Thy words, more clearly than thy works, display,
That, while thy truths my grosser thoughts refine,
I may resemble thee, and call thee mine.[1598]"
FOOTNOTES:
[1582] Compare what is said VOL. I. p. 47--.
[1583] VOL. III. p. 28--. See above, p. 377--.
[1584] See above, p. 546.
[1585] In _Elater_, Fabricius describes 137 species; in _Melolontha_,
149; in one section of _Rhynchænus_, 161; of _Curculio_, 183; and in
his _Papiliones Heliconii_, 300.
[1586] Thus he places _Chlænius holosericæus_ and _nigricornis_,
which might pass for varieties, far asunder; and _Dromius agilis_
is even put in a different section from _D. quadrimaculatus_,
_truncatellus_, &c.
[1587] The continuance of this important privilege, by the lamented
death of the learned President, is now rendered uncertain; but I
trust we may anticipate, that by the liberality of the members of
the Linnean Society, and if necessary of the public, this invaluable
treasure, by being fixed in the Metropolis, will be more than ever
accessible to the British Naturalist.
[1588] It may not be amiss to mention a few:--_Sphæridium
dytiscoides_ is a _Hydrophilus_ related to _H. fuscipes_. _S.
glabratum_ is heteromerous, probably one of the _Helopii_ Latr.
_Carabus retusus_ and _Maderæ_ both belong to _Calosoma_. _Cistela
angustata_ is a true _Choleva_. See _Linn. Trans._ xi. 138.--S.
[1589] See above, p. 406.
[1590] VOL. III. p. 304.
[1591] For dissections the one recommended above, p. 201, may be
used. Sometimes a watchmaker's eye-glass, which also sets the hands
at liberty, will be found useful.
[1592] _N. Dict. d'Hist. Nat._ xxxii. 264.
[1593] _Ibid._ xvi. 281.
[1594] _Ibid._
[1595] _Organic Remains_ iii. _t._ xvii. _f._ 2.
[1596] _Ibid._ 281--.
[1597] VOL. I. p. 20.
[1598] Cowper's _Retirement_.
APPENDIX.
_DE GENITALIBUS ET GENERATIONE INSECTORUM._
Inter tot et tanta OPTIMI CREATORIS miracula, quæ _Regnum Animale_
tantopere illustrant, vix ulla sunt majori admiratione digna,
et Physiologi eruditi introspectione, quam quæ ad generationem
insectorum spectant. Quamvis enim inter sexûs organa vertebratorum
animalium et insectorum analogia haud parva locum habet; numero
tamen, figura et proportione partium, miro modo sæpius differunt; et
organa insuper plura in insectis reperiuntur quorum in vertebratis
exempla frustra quæsiveris.
Hoc argumentum tractando duo sunt imprimis consideranda, _genitalia_
nempe ipsa utriusque sexûs, et _coitus_.
I. De _genitalibus_ in genere prima observatio erit, "quo minor
horum, habita corporis ratione, moles, eo magis nervorum systema,
et cephalicum imprimis ganglium, predominans fit; eo major igitur
intellectûs facultas (instincto naturali consociata) reperitur,"
ut in principibus, _Apibus_ nempe, _Formica_, &c.[1599] In
_Hymenopteris_, iterum, _Dipteris_, et _Neuropteris_, hæc organa
maxime retracta sunt; dum in _Lepidopteris_, _Coleopteris_, et
_Orthopteris_ (quorum insuper mascula et feminea insigniter inter
se congruunt[1600]), magis exserta jacent[1601]. Genitalia plerumque
in extremitate postica abdominis sub _ano_ sita sunt[1602], sed
in _Arachnidis_ et _Libellulinis_ masculis in basi _ventris_, in
_Phalangio_ sub _ore_, et in _Chilognathis_ in anteriore corporis
parte subtus latitant[1603]. Ubi organa duplicantur, ut _testes_,
semper symmetrica sunt. Non obliviscendum est quòd in diversis
generibus habitu externo persimili consociatis, imò in diversis unius
generis speciebus genitalia diversa interdum reperiuntur[1604]: sic
in Lamellicornibus _stercorariis_ (_Scarabæus_, _Copris_, &c.),
testes tantummodo sunt _duo_; in _arboreis_ (_Melolontha_, &c.)
_duodecim_, et in _floralibus_ (_Cetonia_, &c.) _viginti-quatuor_.
Genitalia sunt vel _mascula_ vel _feminea_.
i. Genitalia _mascula_, sunt _penis_; _canalis excretorius_; _vesiculæ
seminales_; _vasa deferentia_; _testes_; _prehensores_; et _semen_.
1. _Penis_[1605] quoad _substantiam_ plerumque membranaceus, at
interdum corneus est, et intus cavernosus[1606]; in _Coleopteris_
apice vagina bivalvi vulvam aperiente instructus est[1607]: _figura_
variat admodum, sæpius tamen cylindricus vel subcylindricus est;
in _Blattis_ apicem versus sensim attenuatus[1608]; in _Cherme
Pyri_ capitatus[1609]; in _Vespa vulgari_ cochleariformis[1610]; in
_Crabrone_ bilobus[1611]; in _Poliste gallica_? incurvus et apice
bicornis[1612]; in _Sarcophaga carnaria_ apice spinosus[1613];
in _Megachile muraria_ difformis[1614]; in _Tyrophaga Casei_ et
quibusdam aliis _Muscidis_, spiralis[1615]; in _Cordulia ænea_
et _Phalangio_ biarticulatus[1616]. Utplurimum nudus est, sed in
_Tephrite_ fimbriatus. In insectis proprie dictis _simplex_ est hoc
organon, in _Scorpionibus_ autem _duplex_ evadit; quod fit etiam in
quibusdam reptilibus, _Serpentibus_ nempe et _Lacertis_[1617].
2. _Canalis excretorius_ e concursu vesicularum seminalium formatur,
et a _pene_ excipitur in quo terminat et cui semen reddit; interdum
brevissimus est, ut in _Blatta_[1618], et interdum iterum prælongus,
ut in _Blapte Mortisaga_, _Tyrophaga Casei_, et aliis[1619].
Plerumque cylindricus est, musculosus, compactus, et externe tracheis
pertextus[1620].
3. _Vesiculæ seminales_ conniventes formant, ut jam dictum est,
canalem excretorium communem cujus prolongatio bifida esse videntur;
vasa deferentia hinc excipiunt. Interdum vasa hæc ac vesiculæ
seminales eodem loco in canali excretorio communi terminant, unde
canalis hic tumidior fit[1621]. Vesiculæ supradictæ maxime variant:
modo canalem exhibent ventricosum, tortum, implexum, longissimum;
modo rectum, breviorem. In plerisque _duæ_ sunt vesiculæ seminales,
etiam in _Lepidopteris_ monorchidis; in quibusdam (_Tenebrione
Molitore_, _Hydrophilo piceo_) _quatuor_[1622]; in aliis
(_Dytisco marginali_) _sex_[1623]; et, in _Locustis_ et _Blatta_,
_plurimæ_[1624]. Breves admodum sunt in _Orthopteris_ et quibusdam
_Coleopteris_[1625]; sed in aliis longissimæ; in _Orycte nasicorni_
vicies, et in _Cetonia aurata_ ter decies corpus longitudine
superant[1626]. In hisce organis semen e testibus per vasa deferentia
acceptum ante emissionem elaboratur.
4. _Vasa deferentia_ ita appellantur quia semen e testibus acceptum
ad vesiculas seminales _deferunt_. Ex utroque teste unum vas deferens
exit, et si utrinque plures sint testes, ut in _Melolontha_[1627],
_Cetonia_, &c., omnia ad unicum utrinque canalem formandum
confluunt, qui vesiculis supradictis semen reddit: interdum, ut in
_Lepidopteris_[1628], ab his nullo modo separantur, unum canalem aut
tubum formantia; sed in aliis penitus sunt distincta[1629]. Ex eodem
filo quo contexuntur testes vasa deferentia sæpius deducuntur.
5. _Testes_ organa sunt semen primum secernentia: variant
_compositione_, _numero_, et _figura_. In quibusdam (_Lepidopteris_
et _Hymenopteris_) sunt compacti vasculis visui se subducentibus;
in aliis (_Orthopteris_, _Neuropteris_, _Dipteris_, et quibusdam
_Coleopteris_) e vasculis brevibus cæcis variique voluminis
conformati sunt, atque tunica densa tenaci vel rete tantum mucoso
obducti[1630]; vel iterum ex unico variisque modis tecto canali varie
contorto et implexo, qui deduci potest et haud raro massam ovalem
trachearum ope contextam refert, conflantur, ut in _Coleopteris
Prædaceis_ tam aquaticis quam terrestribus[1631].
_Numero_ etiam variant testes. Quædam _Lepidoptera_, ut _Pontia
Brassicæ_, item _Iulidæ_[1632], _unico_ gaudent; pleraque tamen
insecta animalia vertebrata hic æmulantur, et testibus instruuntur
_duobus_; in _Nepa cinerea_ et reliquis _Hemipteris_ quatuor vel
quinque[1633], in _Melolontha vulgari_ sex[1634], et in _Cetonia
aurata_ duodecim[1635], utrinque deteguntur. Interdum ex acinis
pluribus compacti videntur, et bacciformes appellari possunt. In
_Lamia_ duodecim glandulæ in utroque teste coalitæ inveniuntur[1636],
et in _Tenebrione Molitore_ plurimæ[1637].
Quoad _figuram_, interdum, ut in _Pontia_ Papilionum genere, spherici
evadunt[1638]; in _Gryllo_ pyriformes[1639]; in _Ape mellifica_
oblongi[1640]; lineares et longissimi in _Procruste coriaceo_, in
quo _decies_ longitudine corpus superant[1641]; in _Nepa cinerea_
sub-ovati, et singuli filamento longo varie convoluto et contorto
terminati[1642].
In _larvis_ etiam hæc organa detegere est. Sic in eruca _Pontiæ_
quatuor testes sunt utrinque, vel potius unicus ex quatuor serie
ordinatis, conflatus[1643]. Hi sensim coacervantur donec in sphæricum
testem antea descriptum coalescant.
6. _Prehensores_[1644] sunt organa figura varia quibuscum mas
in coitu feminæ anum corripit et comprimit. Quoddam analogum in
quibusdam _Mammaliis_, _Avibus_, _Piscibus_, et _Reptilibus_[1645]
invenitur, sed in insectis maxime conspicui. Eorum _situs_,
_numerus_; et _forma_, sunt notandi.
Quoad _situm_--circa foramen per quem prodit penis sub ano plerumque
sunt inserti, sed in _Conope_ cornu prehensorium in segmento ventrali
antepenultimo deprehenditur[1646]; et in _Libellulinis_, præter
prehensores _anales_, par est aliud anum spectans, in secundo _ventris_
segmento pone penis ipsius situm[1647]. Prehensorum _numerus_ minime
constans: plerumque _duo_ sunt, sed in _Cicada_, _unicus_ furcatus
tantummodo videre est[1648]; in _Lepidopteris_ variis, _Conope_,
_Libellulidis_, _tres_ anum armant, difformes tamen[1649]; _duo
paria Culicem_ signant[1650], _Megachilem murariam_[1651], et
_Agrionidas_[1652]; in _Locustis_ veris intra abdomen retracta sunt
hæc organa; in pupa tamen _L. morbillosæ_, in nostro musæo asservata,
_quinque_ apparent; _sex_ in _Formicis_ De Geerius detexit, sed in
cognato genere _Myrmica_, _duo_ tantum[1653]; _quatuor paribus_
postremo _Tipula oleracea_ instructa est. Prehensorum _forma_
multifarie variat, imò haud raro in specie eadem: interdum enim
_prehensioni_ soli hujusmodi instrumenta sunt adaptata, aliis diversæ
figuræ _compressionem_ efficientibus; interdum et utroque munere
funguntur. In _Pontia Brassicæ_, in qua par _unicum_, concavo-convexi
sunt, deltoidei, intus setis rigidis fimbriati, et apice dente
incurvo armati[1654]; in _Acrida varia_ tenues, simplices, recurvi;
in _Spilosomate lubricipeda_, quæ _tribus_ gaudet, laterales sunt
concavo-convexi, ovati, dum intermedius brevior est, triangularis
et unguiculo armatus[1655]; in _Cordulia ænea_, et affinibus, _duo
superiores_ sunt lineares et undulati, et _inferior unicus_ profunde
bifidus[1656]; in _Vanessa Urticæ_ exteriores duo sunt conchiformes,
par autem interius unguiforme[1657]; in _Culice_ superiores longiores
conici hirsuti, inferiores breviores et ut in præcedente unguem
referunt[1658]; in _Tipula oleracea_, in qua _octuplici_ prehensore
anus armatus, valvulæ omnes figura diversæ--par exterius nempe concavum
membranaceum reliquos includens, secundum unguiculatum, tertium
subclavatum, et ultimum fere lunatum[1659]; in _Megachile muraria_,
inter alios diversos, unum par literæ T formam habet[1660]; in _Bombo_
forceps analis bivalvis est intus ramosus[1661]; et in _Panorpa_
cheliformis[1662].
7. De _semine_ ipso insectorum paucula sunt notanda. Fluidum est
spissum, lacteum, granulis repletum; sub lente punctula numerosa,
nigra, oblonga, incurva, in illo deteguntur. Quoad _analysin_ ejus,
neque alkalinum neque acidum est, sed quoddam neutrum inter hos
intermedium. Ex sanie vel sanguine deoxydato, et durante coitu
copiosissime secernitur: in aqua tepida solvitur, et conquassatum
fundum petit: spiritu vini rectificato superfuso flocculi quidam
formantur[1663].
ii. _Genitalia_ feminea _vulva_ excepta antea tractavi[1664], hæc est
tubus subcylindricus, foramine ovali vel lunato ab ano distincto,
cum matrice connexus, et per quem semen in coitu transmittitur.
In _Scorpionibus_ duplicem esse vulvam affirmatur duobus ovariis
connexum[1665].
II. _Coitus._--Coitum insectorum tractaturo paucula de lenociniis
amatoriis, et aliis ejusmodi, quæ antecedunt, sunt prædicenda.
_Olfactu_ mares _Phalænarum_ interdum feminam latentem, uti canis
leporem, odorantur[1666]; splendore phosphorico _Lampyrides_ et
quorundam aliorum insectorum feminæ maritum ad lectum gramineum
prælucent; et huc referri forsan debet plurium cæcus ardor lumina
circumvolandi, vel etiam in lumen irruendi; _sonus_ excitat feminas
_Cicadarum_ et _Gryllinarum_[1667], &c. ad amores, et cantu stridulo
querelisque amatoriis diem ducit mas cupidus, donec sponsa advolat,
et tori foliosi fit haud invita particeps. Sonitu etiam uterque sexus
formidati _Anobii_ mutuo sese provocant ad venerem[1668].