of the sub-classes proved to be correct, seeing it is so totally at
variance with what we have from our childhood been perfectly satisfied
with?[55] It is proved correct, simply and solely by the harmony
with which each flows into each,--with which neighbour meets
neighbour,--comparable somewhat to that exquisite feeling which
induces a man to bend to the peculiarities, and perhaps even little
failings of a friend, until he makes them almost his own. It can
hardly be supposed that the sub-classes naturally fell into the
positions which I have assigned to them, without some little
endeavour, on my part, to produce this harmony. This was far from the
case. The discovery, if it be one, was the result of serious and
deliberate study. Even after arriving at their present state, I have
twice endeavoured to alter these positions, once in hopes of making
some of the Tortrices meet the Papilionidæ, as I had an idea that that
very assiduous and ingenious naturalist, Dr. Horsfield, had mentioned
the discovery of such an approach.[56] In vain, however, did _I_
strive to discover such an approach, in either larva, pupa, or imago,
while these points of resemblance were most abundant between the
Geometræ and Papiliones; the pupa, as though in sport, being now
suspended by the tail, now girted round the waist, now enveloped in a
silken web; sometimes round-headed, sometimes pointed, sometimes
eared; now smooth, anon angulated, black, brown, yellow, pure green,
clouded, or spotted: of these, and a thousand other peculiarities,
which tended to corroborate my ideas of arrangement, I refused
invariably to avail myself, trusting to one guide only, which seems as
steadfast as a rock: that _relation of imago constitutes approach of
divisions; relation of larva is the tie which holds divisions
together_. The second alteration I endeavoured to make, was to place
the Papiliones in the centre, a situation to which their splendour and
magnitude would really appear to give them a title. This idea seems
every way so plausible, and so likely to be proposed by entomologists,
should any such see merit enough in this system to give their
attention to its minutiæ, that I am compelled to consider it more at
large.
[55] This question has occurred.
[56] It is so long since I have seen Dr. Horsfield's
beautiful work, that I will not pledge myself to the
doctor's making this assertion.
To a sub-class selected for a centre, two qualities are indispensably
requisite. They have been previously given from Mr. MacLeay, who, it
will be remembered, discovered that one of each of his five groups
contained types of the other four, besides a type peculiar to itself.
This quality must hold good in any group thus selected for a centre;
it must contain types of the six surrounding groups in the first
place. Now, is this applicable to Papilio? Have we not already
experienced the greatest difficulty in finding three good approaches,
the smallest number which a sub-class can possess? How then can we
hope, by any good fortune in discovery, to make ourselves masters of
three other entirely new ones, and these to sub-classes to which it is
confessedly the most unlike? Phalæna, on the contrary, presents us
with Lasiocampa, Ægeria, Cilix, Lithosia, Apatela and Orgyia, five of
which genera beautifully typify the approximating sub-classes. The
preference on this score then is decidedly with Phalæna.
The second position, that it should contain a type peculiar to itself,
is almost a matter of course; but my own idea is, that the very centre
should not only be a type of the genus, or order, or sub-class, but of
the class itself of which it is the centre. From this position, then,
a further and still more important question arises,--What is the type
of Lepidoptera? The parts which afford the generic characters of
Lepidoptera, and, I believe, generic characters in the perfect state
are the only ones of any value, are these--the mouth, palpi, antennæ
and wings; and, as no medium can constitute a type, the excess of
these characters, whether superlatively or diminutively considered,
must be resorted to as the most probable means we possess of
discovering what this type may really be. First, then, the mouth. In
Lepidoptera, we find two distinct characters in this;--first, its
entire absence; secondly, its being furnished with prodigiously long
antlia. The first character is that of Phalæna, the second that of
Sphinx. Next, the palpi are either entirely obsolete or exceedingly
prominent, the first in Phalæna, the second in Pyralis. Thirdly, the
antennæ are remarkably pectinated, or clavated, or setaceous: the
first character is that of Phalæna, the second that of Papilio, the
third that of Noctua. Fourthly, the wings are enormously expansive in
proportion to the body, or remarkably small,--the first is the
character of Phalæna, the second that of Sphinx. It need scarcely be
added, that all these characters are to be met with in every
intermediate degree of intensity. Now, it appears, that Phalæna
possesses an extreme of each of the four principal characters, Sphinx
of two, Noctua of one, and Papilio of one; therefore Phalæna is the
typical genus, Phalænæ the typical order, and Phalæna the typical
sub-class of Lepidoptera: and a necessary conclusion from this fact
is, the type of Lepidoptera is an insect without antlia or palpi, with
very pectinated antennæ and enormously expansive wings, and we may add
nocturnal flight: so that such peculiar characters as the thick full
body and prodigiously long antlia of Sphinx, the clavate antennæ,
erect wings, and diurnal flight of Papilio, argue a departure from,
and not an approach to, the type.
By a reference to the Diagrams exhibiting the classes of Insecta, and
the sub-classes of Lepidoptera, it will at once be observed, that the
central group in each case contains types of the surrounding groups.
Now after a central group has thrown off a set of six forms, each
representing, in general appearance, some group equally extensive with
such central group, the faculty or power of throwing off such forms
becomes, in a good degree, extinct, or, at any rate, very much
debilitated. This can be no unforeseen, but a perfectly natural, and
absolutely necessary consequence; for taking either of the two classes
which are at present sought after, Lepidoptera and Coleoptera, we must
observe, that did either of them possess as varied forms and
characters as are to be found in Neuroptera, the essential and
distinguishing character of that class, viz. variety, and the
harmonious arrangement of the whole sub-kingdom, would both be
entirely lost; and it would remain for human ingenuity to locate
either of the classes centrally or externally, as caprice, or the love
of differing from others, might dictate. I wish it to be observed,
that Neuroptera, in the genera Psyche, Cloëon, Termes, Psocus and
Mantispa, does not merely assume the form of the genera, Tinea,
Chironomus, Formica, Aphis and Mantis, but actually possesses the
characters and appearance of the classes Lepidoptera, Diptera,
Hymenoptera, Hemiptera and Orthoptera. The obviously homogeneous
character of Lepidoptera and Coleoptera, although, probably,
containing in every sub-class more species than the whole of
Neuroptera, clearly disproves the existence of variety amongst their
contents, equal to that amongst the contents of Neuroptera. Yet the
power, although weakened, is by no means extinct; for, amongst the
central group, Phalæna, we find the sub-classes, Papilio, Sphinx,
Pyralis, Tinea, Noctua and Geometra, most faithfully pourtrayed in
Lasiocampa, Ægeria, Cilix, Lithosia, Apatela and Orgyia, and not
merely the individual genera which may happen to approach. As far as I
can discover, after this second series of types the faculty becomes
much weaker, and, after a third, ceases entirely. A decided difference
existing between the first and second series of types, must on no
account be lost sight of, because it so decidedly proclaims the
superiority of the first: in the first instance, the whole character
of the central type, Libellula, is completely lost in each of the
varying types; whereas, in the second instance, the characters of
Phalæna are preserved most decidedly to the remotest ramifications of
the class, subject, however, to the variations already pointed out.
The natural order, _Cossi_, of which the larva and pupa have been
already described, contains but ten genera, even including those whose
claim to a place in the order is somewhat doubtful; and these ten are
readily referable to six families. The genus, Stygia, of New Holland,
seems from Latreille's description, decidedly to belong to this order.
Speaking of Stygia Australis, he says, "_M. Villiers la considère
comme intermediare entre les Sesies et les Zygènes; mais elle n'a
point de trompe; ses palpes sont ceux de Cossus; ses antennes sont
courtes, et nullement en fuse, et plus analogues a celles de certains
Bombyx qu'a celles des Sesies et des Zygènes_."[57] Now the fact, as
M. Latreille supposes, of having no antlia, argues most forcibly the
impossibility of uniting this genus either with Sphinx or Zygæna; for
the sub-class Sphinx not only possesses the most elongate and
conspicuous antlia of any sub-class, but retains this character to its
very circumference, and imparts it to approaching groups, whose types
will be found entirely aglossate: its similarity therefore in shape to
the Sesiæ, which tribe is generally understood to include the Ægeriæ,
is merely that relation of imago which I have before so repeatedly
pointed out. The situation, which without this genus must have been
vacant, thus filled, gives us a most perfect chain of families
throughout the order, except at the point of connexion with Phalæna, a
point of no consequence, because it too much favours old theories to
be contested.
[57] Règne Animal, tom. V. p. 395.
It is rather remarkable, that in this order no instance should occur
of more than three genera belonging to any one family, a number which
I should hardly suppose complete, because a difficulty must always
occur in placing, as in discovering the typical genus or species,
where the number is confined to three.
The introduction of a new generic name, after what has been said on
that subject, may appear rather an inconsistency, but I found it
indispensable, as the species in question would not bend to either of
the established genera, Trochilium or Ægeria; it will, moreover,
afford those whose labours in this way I have somewhat deprecated, a
fair opportunity for retaliation. The families and their relative
situations, as far as my immature and hastily-formed judgment will
allow me to decide, I have shown in the annexed diagram: but it is now
time for me to describe the species whose situation I am endeavouring
to point out.
Sub-kingdom, INSECTA.
Characters from the imago.
The body is divided into three parts, head, thorax, and abdomen; the
head has two fixed compound eyes, and two moveable antennæ. Insects
have six jointed legs in pairs; they breathe by lateral spiracles.
Class, LEPIDOPTERA.
Characters from larva, pupa, and imago.
Larva polypod, bears no resemblance to the imago; pupa quiescent,
bears no resemblance to the imago. Imago has four scaly wings, and the
mouth aglossate or antliate.
Sub-class, PHALÆNÆ (central).
Characters from larva, pupa, and imago.
All varying (the universal character of such central groups).
[Illustration: GENERA OF THE NATURAL ORDER COSSI.]
Natural order, COSSI.
Characters from the larva and pupa.
Larva depressed, kaned; has sixteen feet, lives through one or more
winters, never rolls itself in a ring when touched, feeds on the solid
interior woody parts of vegetables; pupa changes in a tough cocoon, in
which are interwoven particles of the larva's food; it has a double
row of small raised denticulations on each segment of the abdomen,
which give it partially the power of locomotion.
Family ÆGERIIDÆ, Stephens.
Characters from the Imago.
Palpi triarticulate, incrassated at the base, acuminate at the apex,
prominent, enclosing the antlia; antennæ, sub-cylindric, gradually
incrassated from the base nearly to the apex, the apex itself
acuminate and terminated with a fascicle of hairs; ocelli, two. Flight
diurnal in the hottest sunshine.
Genus MEMYTHRUS.--_Sphinx_, Linn.; _Sesia_, Laspeyres; _Ægeria_, Fab.
Characters from the imago.
Palpi very prominent, and densely clothed with scales at the base, in
appearance angulated; antlia fine, not so long as the antennæ; antennæ
the length of the thorax, in the male much pectinated, in the female
simple; superior wings clothed with scales, inferior hyaline.
Sp. 1. MEMYTHRUS VESPIFORMIS.--_Sphinx Vespiformis_, Linn. Syst. Nat.
II. p. 804, n. 31. _Ægeria Asiliformis_ of Fabricius, and other
authors.
Characters from the imago.
Palpi black, yellow at the apex; antennæ black, beneath testaceous;
fulvous at the base; head black, excepting a white mark before each
eye; a yellow ring round the neck; thorax black, with a yellow spot at
the base of each superior wing; abdomen black, slightly barbate, with
three equidistant yellow belts; superior wings deep fuscous, inferior
hyaline; femora and anterior tibiæ black, posterior tibiæ and all the
tarsi yellow.
Inhabits England, but is very rare.
Sp. 2. MEMYTHRUS CRABRONIFORMIS.--_Sesia crabroniformis_, Lasp.
Inhabits Italy.
Sp. 3. MEMYTHRUS CRASSIPES.--_Sphinx crassipes_, Drury.
Inhabits Africa.
Sp. 4. MEMYTHRUS TIBIALIS.--_Ægeria tibialis_, Fab.
Sp. 5. MEMYTHRUS ----?--Unnamed in the Linnæan cabinet.
Several other species probably exist, with which I have not happened
to meet.
The principal distinctions between Memythrus and Ægeria are, that the
antennæ in the former are not longer than the thorax; in the latter
they are much longer; in the males of the former genus they are
decidedly pectinated, in those of the latter but obscurely ciliated;
in the former the anterior wings are always opaque, in the latter
always hyaline.
_Natural Divisions to which the_ SPHINX VESPIFORMIS _of Linnæus is
referable._
FIRST PRIMARY GROUP ANIMALIA.
FIRST KINGDOM ANNULOSA.
CENTRAL SUB-KINGDOM INSECTA.
FIRST CLASS LEPIDOPTERA.
CENTRAL SUB-CLASS PHALÆNA.
SECOND NATURAL ORDER COSSI.
SECOND FAMILY ÆGERIIDÆ.
SECOND GENUS MEMYTHRUS.
FIRST SPECIES VESPIFORMIS.
FINIS.
R. CLAY, PRINTER, BREAD-STREET-HILL.
DIRECTIONS FOR PLACING THE DIAGRAMS.
1. The Classes of Insecta to face page 21.
2. The Sub-classes of Lepidoptera to face page 31.
3. The Natural Order of Cossi to face page 52.