body, having a large head armed with two sharp falciform mandibles,
and furnished with six granular eyes on each side._ This kind he
denominates _Chilopodiform_, as having for its type in the _Ametabola_,
_Scolopendra_ L. The examples he gives are _Carabus_ and _Dytiscus_.
2. _A herbivorous hexapod larva, with a long and almost cylindrical
body, so fashioned that the posterior extremity being curved under
the breast, the animal when at rest necessarily lies like an IULUS
on its side._ This tribe he denominates _Chilognathiform_, from
_Iulus_ L. His examples are, the larvæ of _Petalocerous_ insects, as
_Scarabæus_ L., _Lucanus_ L. &c.
3. _An apod larva, having scarcely the rudiments of antennæ, but
which is furnished instead of feet with fat fleshy tubercles; which,
when continued along the back and belly, give the animal a facility
of moving in whatever way it may be placed._ These he denominates
_Vermiform_, from certain of the _Vermes intestina_ and _Mollusca_ of
Linné which he has associated with his _Annulosa_[378]. His examples
are, _Curculio_ L. and _Cerambyx_ L.
4. _A hexapod and distinctly antenniferous larva, with a subovate
rather conical body, of which the second segment is longer and of
a different form from the others, so as to give the appearance
of a thorax._ His denomination for these is _Anopluriform_, from
_Pediculus_ L., forming Dr. Leach's _Anoplura_. His examples are,
_Coccinella_ and _Chrysomela_ L.
5. _A hexapod antenniferous larva of an oblong form, having like
the former vestiges of a thorax, besides two or more articulated or
inarticulated setaceous or corneous appendages to the last segment of
the abdomen._ This tribe he calls _Thysanuriform_, from _Lepisma_ and
_Podura_ L., forming M. Latreille's order _Thysanura_. His example is
_Meloe_ with a note of interrogation[379].
The system here stated, of naming and characterizing larvæ from the
resemblance and analogy, in many cases very striking, that they bear
to the apterous tribes, is a very happy and original one, and does
its author great credit; yet I think in some instances, as I shall
soon have occasion to point out to you, the application of it is
not so happy as the first idea. But this is always the case when a
new law of nature is discovered; the proper application of it is
gradually developed, and it does not at all detract from the merit of
the first discoverer, that all the bearings of such law do not strike
him as it were intuitively.
Having, however, got the vantage-ground afforded by this discovery
of my friend, let us see if by standing upon it we cannot get a
tolerable generalization of the larvæ of all orders of insects
that undergo a metamorphosis. But first I must observe, that as in
the perfect animals, so in their larvæ, the different groups are
connected by certain _transition_ species, exhibiting characters
common to two or more of them; and likewise that in many cases, which
you will see as we proceed, the analogy is as strong or stronger
between them and the _Crustacea_ (and in a few instances _Arachnida_,
and even _Mollusca_) than the _Ametabola_. My denominations,
therefore, will be taken from those tribes where the analogy appears
to me the most striking, and not from the _Ametabola_ alone.
I shall begin by drawing up for you a list of the Primary forms
that I seem to have observed, and their characters; and then going
through the orders, shall give you the examples of each, with such
observations upon them as the case may require.
_Primary Forms of Larvæ._
APTERA. ARACHNIDA. CRUSTACEA.
ANOPLURIFORM. ARANEIDIFORM. ISOPODIFORM.
THYSANURIFORM. ONISCIFORM.
CHILOPODIFORM. IDOTEIFORM.
CHILOGNATHIFORM. AMPHIPODIFORM.
STOMAPODIFORM.
MOLLUSCA. ANNELIDA. DECAPODIFORM.
BRANCHIOPODIFORM.
LIMACIFORM. VERMIFORM.
_Characters._
1. _Anopluriform._ Carnivorous; hexapod; antenniferous:
with a shortish oblong depressed body, and distinct
thoracic shield. Example: _Psocus_, _Coccinella_, most
_Hemiptera_[380].
2. _Thysanuriform._ Polyphagous; hexapod; antenniferous: body
with segments of trunk distinctly marked; anus often
furnished with setæ or mucro. Ex. _Meloe_[381]? _Thrips_,
_Aphis_.
3. _Chilopodiform._ Carnivorous; subhexapod; antenniferous: body
depressed, elongate, linear, with falcate acute mandibles,
a distinct thoracic shield, and an anal proleg. Ex.
_Cicindela_[382]? _Carabus_ L.
4. _Chilognathiform._ Herbivorous; body subcylindrical,
elongate, linear; no thoracic shield; often many prolegs,
sometimes a retractile one, and sometimes none.--Ex.
_Elater_, _Petalocera_, most _Lepidoptera_, _Tenthredo_
L.[383]
5. _Vermiform._ Polyphagous; apod or hexapod: with very short
legs; antennæ nearly obsolete; body fleshy, plicate, with
sides often plicato-papillose; no distinct thoracic shield.
Ex. _Curculio_ L., _Cerambyx_ L., _Musca_ L., and many other
_Diptera_[384].
6. _Araneidiform._ Carnivorous; hexapod: body very short;
mandibles long, suctorious; animal lying in wait for its
prey in a pitfall it has prepared; motion retrogressive. Ex.
_Myrmeleon_ L.[385] _Cicindela_?
7. _Isopodiform._ Saprophagous; hexapod; antenniferous, with
longer antennæ: body oblong; thoracic shield distinct; anus
styliferous or laminiferous. Ex. _Blatta_ L. _Silpha_ L.?
8. _Onisciform._ Herbivorous; polypod; antenniferous: body
short, oblong, depressed, margined. Ex. _Erycina_, _Lycæna_,
in the _Lepidoptera_, and some species of _Tenthredo_ L.[386]
9. _Idoteiform._ Subcortical; hexapod; antennæ obsolete: body
much depressed, with the last segment elongate, terminating
in three or more mucros. Ex. Larva from Brazil. Perfect
insect at present unknown.
I have placed this larva, which was described above[387], amongst
crustaceous forms, because of the remarkable resemblance which the
last segment of the body bears to that of the _Idoteidæ_; but I do it
with considerable hesitation, since in other respects its type seems
to be in the _Ametabola_. In its want of antennæ, very short legs,
and ventral asperities, it resembles some of the _Vermiform_ larvæ;
in its small head, distinct thoracic shield, and oblong shape, it
approaches the _Anopluriform_; and in its very depressed body, but
not at all in other respects, the _Chilopodiform_. At any rate, it
appears of a primary Type.
10. _Læmodipodiform._ Herbivorous; hexapod; antenniferous, with
long antennæ: body elongate, subcylindrical; second segment
of the trunk the longest; anterior pair of legs distant from
the other two. Ex. _Phasma_.
11. _Amphipodiform._ Herbivorous; hexapod; antenniferous, with
long antennæ: body shortish, compressed, saltatorious. Ex.
_Gryllus_ L.[388]
12. _Stomapodiform._ Carnivorous or saprophagous; hexapod;
antenniferous, with long antennæ: body elongate,
subdepressed, with raptorious hands, and abdomen wider than
the trunk; in aquatic species furnished with lateral gills.
Ex. _Mantis_, _Ephemera? Sialis?_
13. _Decapodiform._ Carnivorous; hexapod; antenniferous: body
elongate, narrow, convex, compressed, tapering towards the
tail; tail with natatorious laminæ. Ex. _Dytiscus_ L.,
_Agrion_ F.[389]
14. _Branchiopodiform._ Carnivorous?; aquatic; apod;
antenniferous: head distinct: body transparent, flexile,
furnished with a respiratory tube just above the tail. Ex.
_Culex_[390].
15. _Limaciform._ Herbivorous; apod, or with very short legs:
body ovate or obovate, slimy. Ex. _Apoda_ Haw., _Tenthredo
Cerasi_ L.
The above are the principal forms that appear to me _Primary_ (though
some doubt may rest upon the ninth and tenth); and probably others will
hereafter be discovered, since at present our knowledge of the larvæ
of most of the Orders is very limited. And now having given you this
generalization of them, as far as they are known to me, I shall next,
in a slight survey of those of the different orders, lay before you
what I have further to observe upon this subject.
_Coleoptera._ The _Anopluriform_ coleopterous larvæ, according to
Mr. W. MacLeay's view of them, include both those of _Coccinella_
L., _Chrysomela_ L., and _Cassida_ L.; but this appears to me to
admit of further consideration. With regard to the two former--those
of _Coccinella_ are carnivorous, those of _Chrysomela_ herbivorous;
the first is also usually more flat and depressed. As to the latter,
_Cassida_[391], it seems to me to belong to a peculiar type,
distinguished not only by its radiated margin, but by the remarkable
deflected anal fork on which it carries its excrement. At present I
know no analogous form amongst the apterous tribes; I must therefore
leave this without a denomination. Perhaps the larva of _Hispa_ or
_Alurnus_, when known, will throw light upon this subject. The larva
of _Endomychus_ agrees with that of _Coccinella_.
There are very few known larvæ that approach to a true
_Thysanuriform_ type in this order: that most celebrated is the
one supposed to belong to _Meloe_; but the claim of this to be so
considered, is, as we have seen, rather dubious. Should this point
at last be satisfactorily ascertained, it will probably carry with
it the whole tribe of vesicatory beetles. But even this animal in
its _general_ structure is _anopluriform_: the only circumstance
that gives it any analogy to the _Thysanura_ being its anal setæ.
Mr. William MacLeay is inclined to regard some of the larvæ of the
_Malacodermi_ Latr., but which of them he does not state, as probably
belonging to the tribe in question[392]. Those of _Lampyris_ and of
_Telephorus_, as described and figured by De Geer[393], appear to me
intermediate between the _Anopluriform_ and _Chilopodiform_ Types:
they have no anal setiform or styliform appendages, their mandibulæ
are falcate, and their habits seem carnivorous.
Examples of _Chilopodiform_ coleopterous larvæ are more numerous.
Of this description are those of _Gyrinus_, _Cicindela_, _Carabus_,
and _Staphylinus_. That of the first, indeed, appears to be the
most perfectly _Scolopendriform_ of any yet known; yet the gills
or respiratory laminæ, a pair of which issues from each abdominal
segment, and two pair from the last[394], prove that there is no
slight analogy between it, and indeed many other aquatic larvæ,
and the _Stomapoda_ amongst the _Crustacea_. A remarkable instance
of analogy with the _Decapoda_ of the same _Class_ is presented
by the larva of _Dytiscus_, &c. which Mr. MacLeay considers as
_Chilopodiform_, but which exhibits no other resemblance to
_Scolopendræ_ than in its predaceous habits and threatening aspect.
Its convex, compressed, tapering body, terminating in setæ or laminæ,
is certainly much more like that of a shrimp or a prawn; to which
the older Entomologists thought it was akin[395], and after which
they named it. As Mr. MacLeay's object was, to take all his forms
from the _Ametabola_, perhaps these larvæ will best fall in with his
_Chilopodiform_ type; though in the general form of their body they
most represent a section (_Lepisma_ L.) of the _Thysanura_.
_Chilognathiform_ forms are equally numerous in the Coleoptera with
the preceding. The wire-worm, or larva of _Elater Segetis_, as to
shape best represents the full-grown _Iulus_[396], and those of the
_Petalocera_ (_Scarabæus_ L., _Lucanus_ L.) the young one.
The most abundant of all forms in this order, is, I think, the
_Vermiform_, upon which I have nothing further to remark.
With regard to _Crustaceous_ forms in _Coleoptera_, besides the
_Decapodiform_ just noticed, I possess two specimens of larvæ of
_Silphidæ_ which seem to exhibit a considerable analogy with the
_Isopodous Crustacea_, one rather convex and the other flatter, so
as to give the idea of an _Armadillo_ and of an _Oniscus_.
_Strepsiptera._ Larva _Vermiform_.
_Dermaptera._ Larva _Thysanuriform_. Type _Podura_ or _Sminthurus_.
_Orthoptera._ Mr. MacLeay considers the larvæ of this Order as
primarily _Thysanuriform_[397], though he allows the resemblance
between them and _Amphipoda_ to be particularly striking[398]. For
my own part, their prototypes appear to me to be in the _Crustacea_,
and their analogical relations to the _Thysanura_ much more distant.
I trust this will appear to you the reverse of dubious in a progress
through the Crustaceous Orders. I begin with the _Isopoda_. Take the
larva of a _Blatta_, and place it between a _Lepisma_, or _Machilis_,
and an _Oniscus_, or _Porcellio_; you will find that in shape and
width, and the form of its anal styles, it resembles the latter
much more than it does the former, with which it possesses scarcely
any character in common, except its multiarticulate antennæ. It is
remarkable, that amongst the _Blattidæ_ we meet with species that
represent both the _Oniscidæ_ and _Armadillo_ or _Glomeris_[399], the
latter being more convex than the former. In their habits the Blattæ
certainly agree with _Lepisma_; and Dumeril, who thought the latter and
_Podura_ subject to a metamorphosis, imagined they were related[400].
The Spectres of Stoll (_Phasma_ F.) are so strikingly analogous
to another crustaceous tribe, the _Læmodipoda_, particularly the
genus _Caprella_, that Montagu gave one species the Trivial name of
_Phasma_[401]. The jumping _Amphipodiform_ Crustacea are represented
extremely well by _Gryllus_ L., and the _Stomapodiform_, particularly
_Squilla Mantis_, by _Mantis_. The resemblance in this last instance
is so very striking, that it cannot escape the eye of the least
intelligent observer. Orthopterous insects may perhaps one day
be discovered analogous to the two other crustaceous orders, the
_Decapods_ and _Branchiopods_; but at present I know of none of that
description.
_Hemiptera._ The larvæ of this order, which in general resemble the
perfect insect, except that they have no wings, seem most commonly to
belong to the _Anopluriform_ type[402]; but the _Aphides_, _Chermes_,
and _Thrips_ may, I think, be regarded as more analogous to the
genera _Podura_ and _Sminthurus_ in the _Thysanura_[403]. I have
some suspicion that the _Nepidæ_, _Naucoris_, and the remipedes,
_Notonecta_, _Sigara_, &c. may find their prototypes amongst the
_Crustacea_; but my confined knowledge of the latter does not enable
me to point to any individual genera or tribes that they may be
presumed to represent.
_Neuroptera._ As the kinds of larvæ of the different tribes
composing this order, as it now stands, are very various, it is to
be expected that the analogical forms they represent are equally
so. The _Libellulina_ MacLeay (whose metamorphosis that gentleman
has denominated _subsemicomplete_, a term warranted by their
losing in their perfect state the mask before described[404]) in
their oral organs, particularly by their galeate _maxilla_ and
distinct _ligula_[405], have some relation to the _Orthoptera_, the
prototypes of whose larvæ we have found amongst the _Crustacea_:
probably, therefore, those of the tribe in question lurk in that
class; a suspicion that receives strong confirmation from the larva
of _Agrion_[406], which in its tapering body and anal natatorious
laminæ represents a shrimp. The larvæ of that very peculiar and
distinct tribe, the _Ephemerina_, appear to be intermediate between
the _Stomapodiform_ and _Thysanuriform_ types. Their natatory
respiratory abdominal laminæ seem copied from the former, and their
anal diverging setæ from the latter[407]. The _Myrmeleonina_, as
well in their general form as in their motions and habits, present
a most singular analogy with the tribe of spiders, as does also in
some respect that of _Cicindela_. With regard to _Panorpa_, which
Mr. MacLeay remarks is related to _Myrmeleon_[408], and is a most
ferocious insect[409], as its larva has not yet been discovered,
nothing certain respecting its analogical form can be asserted; but
should it, like the male fly, represent the scorpion, both orders
of _Arachnida_ will have their representatives in the class we are
considering. The _Corydalina_, as far as the larva of _Hemerobius_
instructs us, is _Chilopodiform_, but with a tendency to the
_Araneidiform_ Type. The _Ametabola_ also furnish the prototype
of the next tribe, the _Termitina_, which, as is evident both
from _Psocus_ and _Termes_, are perfectly _Anopluriform_. The
_Sialina_, or _Plicipennes_ of Latreille, excluding _Trichoptera_
Kirby, appear to me to be intermediate between the _Chilopodiform_
and _Stomapodiform_ Types, and not without some relation to the
_Thysanuriform_. Their pediform, jointed, respiratory abdominal
appendages, their head and falcate mandibles, seem copied from
the first tribe. The same appendages considered as organs of
respiration, and their taper forks, are moulded upon the plan of the
_Stomapodiform Crustacea_, and the long seta which terminates the
abdomen is upon the _Thysanuriform_ plan[410].
_Trichoptera._ The larvæ of this order appear also to be constructed
upon a double plan. The respiratory threads observable in both the
upper and under sides of the abdomen connect it with the _Stomapoda_,
and its cylindrical elongate body with _Chilognathiform_ types in the
_Lepidoptera_[411].
_Lepidoptera._ The great majority of larvæ in this order are
_Chilognathiform_, but there are exceptions to this remark. Those
of the _Geometræ_ recede from this type, both in their motions and
the distance and number of their legs. In both these respects they
represent the _Læmodipoda_ in the _Crustacea_[412]. Other caterpillars
are _Onisciform_; and a third sort seem to leave the _Annulose_ type,
and imitate that of the _Mollusca_, and one is figured by Madame
Merian[413] which appears to tend even to the _Chilopodiform_ type.
_Hymenoptera._ In this order the larvæ of the saw-flies, _Tenthredo_
L., are in general _Chilognathiform_, though some are _Onisciform_,
others _Limaciform_, and those of _Lyda_ F. (_Cephaleia_ Jur.) and
_Sirex_[414] have a _Vermiform_ tendency, and are a stepping-stone to
those of the rest of the order, which are all _Vermiform_ and apods.
_Diptera._ The majority of this order may be set down as _Vermiform_,
though it is not improbable that some of them bear an analogy to
animals that appear far removed from the _Annulosa_. Thus, the larva
of _Stratyomis Chameleon_ seems to exhibit no small resemblance to
some of the _Polypi vaginati_ in the _Acrita_ subkingdom of Mr. W.
MacLeay[415]. That of _Culex_ and some others is constructed on a
quite different type from the rest, and seems to possess some analogy
to the _Branchiopod Crustacea_.
Though some of these analogies are more striking than others, yet
in almost all that I have stated there is that kind of resemblance
that could not be the result of what is called mere chance; and Mr.
MacLeay, by first pointing out this plan of the All-wise Creator,
and by laying down the doctrine of _analogies_ in general, as
distinguished from _affinities_ in the animal kingdom, has furnished
the believer with a new argument against those attacks of the
infidel, that would render null those proofs of the wisdom and
goodness of the Author of nature with which the animal and vegetable
creation furnish us; by affirming most absurdly, and under the
most stultifying blindness of mind, that the _creatures_ were in a
manner their own _creators_, their wants under local circumstances
stimulating them to efforts that in a long course of years produced
all the different forms and organizations that are now to be found
in our globe. The affinities and close connexion of beings with
each other, so that the ascent from low to high is usually by
the most gentle gradations, is the circumstance on which they
build this strange and impious theory. But the fact, that certain
animals of one tribe were created with a view to certain animals
of another, so as to present a striking aspect of correspondence,
parallel almost with that of type and antitype, without any real
affinity or approximation;--this triumphantly proves a Power above
and without them, who has associated them not only in a complex
chain of affinities, but has caused them to represent and figure
each other, even when evidently far removed, so as to give a mutual
correspondence and harmony to the whole, which could be produced only
by a Being infinite in power and wisdom, who made all things after a
general preconceived plan and system.
iv. We are now to consider the _clothing_ with which larvæ are
furnished. Many are quite naked, and smooth or rough only with granular
elevations or tubercles orderly arranged; but a very considerable
number, especially of the _Lepidoptera_ order, are clothed with hair
or bristles of different kinds, in greater or less abundance, and
arranged in different modes; and a proportion still smaller have their
skin beset with spines or a mixture of spines and hairs. Lyonnet found
that the hairs of the caterpillar of the great goat-moth (_Cossus
ligniperda_) were hollow, though not to the apex: probably this is the
case with those of other larvæ, as well as with their spines. In this
instance they were set, he observes, in a corneous ring, or very short
cylinder, elevated a little above the skin. The hair passes through
this ring, and appears to be rooted in a soft integument, which clothes
the skin within, and upon which the nerves form a reticular tissue,
some of which he thinks he has even seen enter the root of the hairs,
which perhaps are organs of touch[416].