from the atmosphere into the abdomen, is attended by the constriction
or expansion of that part as it rises or falls in flight[890], which
seems to require the action of constrictor and laxator muscles.
iv. The _Viscera_. Having before had occasion sufficiently to notice
the muscles by which the systole and diastole of the _dorsal vessel_
of insects is maintained[891], I shall now only mention those that
are _woven_ round their alimentary canal, by which the peristaltic
motion of that organ, causing its contractions and the propulsion of
its contents, takes place. One would at first think that a view of the
_intestines_ of any animal could under no circumstances afford any
very pleasing spectacle to the eye of any but a scientific spectator;
but any _lady_ who is fond of going to Disons to be tempted with an
exhibition of fine lace, would experience an unexpected gratification
could she be brought to examine those of a caterpillar under a
microscope: with wonder and delight she would survey the innumerable
muscular threads that in various directions envelope the gullet,
stomach, and lower intestines of one of these little animals; some
running longitudinally, others transversely, others crossing each
other obliquely, so as to form a pattern of rhomboids or squares;
others again, surrounding the intestine like so many rings, and
almost all exhibiting the appearance of being woven, and resembling
fine lace,--one pattern ornamenting one organ; another, a second; and
another, a third. This will suffice to give some idea of this part of
the muscular structure of these little animals[892].
Lyonet counted the muscles contained in the body of the caterpillar
of the _Cossus_. In the head he found 228; in the body, 1647; and
enveloping the intestines, no less than 2186; which, after deducting
20 that are common to the gullet and the head, gives a total of
4061[893]. In the human subject only 529 have been counted[894]: so
that this minute animal has 3532 muscles more than the Lord of the
creation!
* * * * *
The muscles of the _Arachnida_ seem less numerous than those of
insects. In the _Scorpionidea_ they appear to be robust, formed of
simple straight fibres, of a whitish gray colour: a muscular web,
rather strong, clothes the _parietes_, but rarely adheres to them,
of the abdomen, and envelopes the _viscera_, with the exception of
the lungs, and probably of the heart. The dorsal part of this web
gives birth to seven pairs of filiform muscles, which traverse the
liver, and are attached to a muscular riband which, passing above
the lungs, runs the whole length of the ventral _parietes_. These
muscles when exposed to view resemble extended cords. The abdominal
segment preceding the tail is filled with a powerful muscular mass
which moves that organ[895]. Treviranus discovered two longitudinal
muscles in _Scorpio europæus_, running from the breast to the tail,
which above and below each gill were connected by another running
transversely across the heart, thus forming a quadrangular area in
which the gills are situate[896]. The heart appears to be moved by
muscles not very dissimilar to those of the _Cossus_[897], as is
likewise that of the _Araneidea_; in _Clubiona atrox_ the wider part
of this organ is muscular, and incloses a considerable cavity[898].
In this tribe the muscles of the abdomen, the skin of which is soft
and unfit to act as a lever to them, are attached to a cartilage, and
thus their action is better sustained[899].
Having thus laid before you all of importance that I can collect
with regard to the apparatus of muscles discoverable in insects,
I shall next say something upon a few other points connected with
that subject. When I enlarged upon their _motions_, I related a
few instances of the extraordinary power of that apparatus[900] in
_leaping_ ones; but this power is not confined to that circumstance.
The _flea_, not more remarkable for its compressed form, enabling
it to glide between the hairs of animals, and its elastic coat of
mail, by which it can resist the ordinary pressure of the fingers,
than for its muscular strength, has attracted notice on this account
from ancient times. Mouffet relates that an ingenious English
mechanic, named Mark, made a golden chain of the length of a finger,
with a lock and key, which was dragged by a flea;--he had heard of
another that was harnessed to a golden chariot, which it drew with
the greatest ease[901]. Another English workman made an ivory coach
with six horses, a coachman on the seat with a dog between his
legs, a postillion, four persons in the coach, and four lacqueys
behind--which also was dragged by a single flea. At such a spectacle
one would hardly know which most to admire, the strength and agility
of the insect, or the patience of the workman. Latreille mentions a
flea of a moderate size dragging a silver cannon on wheels, that was
twenty-four times its own weight, which being charged with powder,
was fired without the flea appearing alarmed[902]. Many caterpillars
are accustomed to extend their bodies from a twig, supported merely
by the four hind feet, in one fixed attitude, either in an oblique,
horizontal, or vertical direction, either upwards or downwards, and
that for hours together. We may conceive what prodigious muscular
force must be exerted upon this occasion, by reflecting that the
most expert rope-dancer, though endued with the power of grasping
with his feet like a bird with its claws, could not maintain himself
in a horizontal position even for an instant. Bradley asserts that
he has seen a stag-beetle carry a wand half a yard long and half an
inch thick, and fly with it several yards[903]. Some insects have the
faculty of resisting pressure in a wonderful degree. If you take a
common dung-chafer (_Geotrupes_) in your hand and press it with all
your strength, you will find with what wonderful force it resists
you; and that you can scarcely overcome the counteraction, and retain
the insect in your hand: was it not for this quality, the grub of
the gad-fly must be crushed probably in passing through the anal
sphincter of the horse[904]. But that of _Eristalis tenax_ affords
a more surprising instance of this power of counteraction:--an
inhabitant of muddy pools, it has occasionally been taken up with
the water used in paper-making, and strange to say, according to
Linné, has resisted without injury the immense pressure given to
the surrounding pulp[905]; like _leather-coat Jack_ mentioned by
Mr. Bell[906], who, from a similar force of muscle, could suffer
carriages to drive over him without receiving any injury. Almost
as remarkable is the state of extreme relaxation into which the
muscles of some larvæ fall, when their animation is suspended; and
the revived tension to which a subsequent resumption of the vital
powers restores them. Bonnet having suspended the animation of the
caterpillar of _Sphinx Ligustri_ by keeping it submerged, squeezed
it between his fingers, until it had wholly lost its cylindrical
form and was as flat and supple as the empty finger of a glove; yet
in less than an hour the very same caterpillar became as firm, as
compact, as cylindrical, and in short, as well, as though it had
never been submitted to treatment so rough[907].
It is fortunate that animals of a large size, as has been well
remarked, especially noxious ones, have not been endowed with a
muscular power proportionable to that of insects. A _cockchafer_,
respect being had to their size, would be _six_ times stronger than
a _horse_; and if the _elephant_, as Linné has observed, was strong
in proportion to the _stag-beetle_, it would be able to pull up rocks
by the root, and to level mountains[908]. Were the _lion_ and the
_tiger_ as strong and as swift for their magnitude as the _Cicindela_
and the _Carabus_, nothing could have escaped them by precaution, or
withstood them by strength. Could the _viper_ and the _rattlesnake_
move with a rapidity and force equivalent to that of the _Iulus_ and
_Scolopendra_, who could have avoided their venemous bite? But the
CREATOR in these little creatures has manifested his Almighty POWER,
in showing what he could have done had he so willed; and his GOODNESS
in not creating the higher animals endued with powers and velocity
upon the same scale with that of insects, which would probably
have caused the early desolation of the world that he has made.
From this instance we may conjecture, that after the resurrection,
our bodies by a change in the structure and composition of their
muscular fibre--for we know that their locomotive powers and organs,
as far as the muscle is concerned, will then be of a very different
nature[909]--may become fitted for motions and a potent agency of
which we have now no conception.
This wonderful strength of insects is doubtless the result of something
peculiar in the structure and arrangement of their muscles, and
principally their extraordinary power of contraction, excited by the
extent of their respiration: for animals that respire but little, as
the fœtus in the womb and the pullet in the egg, have very little
contractile muscular power[910]. To get some idea from facts of this
extraordinary contractile power in insects,--extract the sting of a bee
or a wasp, with its muscles, which appear to be attached to powerful
cartilaginous plates[911], and you will find it continue for a long
time to dart forth its spicula, almost as powerfully as when moved
by the will of the animal. A still more extraordinary instance of
irritability is exhibited by the _antlia_, or instrument of suction of
the butterfly. If this organ, which the insect can roll up spirally
like a watchspring or extend in a straight direction, be cut off as
soon as the animal is disclosed from the chrysalis, it will continue
to roll up and unroll itself as if still attached to its head: and if
after having apparently ceased to move for three or four hours it be
merely touched, it will again begin to move and resume the same action.
This surprising irritability and contractility of muscle doubtless
depends upon the peculiar structure of the antlia, which is composed of
an infinite number of horny rings, acted upon by muscles, more numerous
probably than those which move the trunk of the elephant. The motion
only ceases when the muscles become dry and rigid.
* * * * *
I have already, under another head[912], considered the _annual_
sleep, or winter state of torpidity of insects, during which an
intermission for the most part of muscular motion and action takes
place. I shall now make a few observations with respect to their
_diurnal_ sleep, which may very properly have its place in the
present letter. That insects, usually so incessantly busy and moving
in every direction, require their intervals of repose, seems to
call for no proof. We see some that appear only in the _day_, and
others only in the _night_, others again only at certain hours;
which leads to the conclusion, that when they withdraw from action
and observation, it is to devote themselves to rest and sleep. The
cockchafer flies only in the evening; but if you chance to meet
with it roosting in a tree in the earlier part of the day, you will
find it perfectly still and motionless, with its antennæ folded and
applied to the breast:--we cannot indeed say that its eyes are shut;
for as insects have no eyelids, that sign of sleep can never be found
in them. Again, if a Lepidopterist goes into the wood to capture
moths in the day-time, he finds them often perched on the lichens
that cover the north side of the trunk of a tree, with their wings
and antennæ folded, and themselves without motion, and insensible of
his approach and their own danger. Thus it was that I captured that
rare insect the lobster-moth (_Stauropus Fagi_) in the New Forest.
Some, however, have asserted that the caterpillar of the silkworm,
except when they moult, never intermits feeding day or night, and
consequently does not sleep: but the accuracy of this statement, both
from analogy and observation, admits of great doubt. Malpighi informs
us that these caterpillars for an hour and more, twice a day, remain
immoveable with their heads bent down as though asleep, and even if
disturbed, resume again the same inactive posture[913]; and other
larvæ in great numbers certainly seem to have regular intermissions
from eating of considerable duration: those called Geometers, for
hours together remain motionless projected from a twig, to which
they adhere by their posterior prolegs alone; and the processionary
caterpillars make only _nightly_ sorties from their nests, passing
the day in inaction and repose[914]. Bees have been often seen by
Huber, when apparently wearied with exertion, even in the middle of
the day, to insert the half of their bodies into an empty cell, and
remain there, as if taking a nap, without motion for half an hour
or longer[915]; and at night they regularly muster in a state of
sleep-like silence. Mr. Brightwell once observed an individual living
specimen of _Haltica concinna_, which appeared to remain motionless
on the same spot of a wall for three successive days.
Before concluding these remarks on the Internal Anatomy and
Physiology of Insects, I shall explain to you, as you will probably
feel inclined occasionally to pursue the subject, the best mode of
_dissecting_ them.--By far the most useful dissecting instruments
for this purpose are very fine-pointed and sharp _scissors_, as
these will enable you to divide the integument and separate other
parts with much less risk of injuring their delicate structure than
any knife. These scissors are what Swammerdam chiefly used; and he
had some so extremely small and fine, that he was necessitated to
employ a lens when he sharpened them. If to these be added a sharp
and fine-pointed _knife_ or two, some _needles_ fixed in handles,
also fine-pointed--(you will find them more convenient than any other
instrument for detaching minute parts and fibres,) a pair of fine
and accurately adjusted _pliers_, and an assortment of camel's-hair
_brushes_,--you will be nearly set up as an Entomological dissector.
You will still, however, require a small dissecting table, with a
projecting and moveable arm for lenses of various descriptions, so
as to admit both the hands to be employed upon the subject under
examination; and for this purpose probably no contrivance can be
better adapted than that of Lyonet, of which the figure in Adams _On
the Microscope_ will convey a better idea than any description[916].
Previously to dissecting any insect, it must be killed by plunging
it into boiling water, which is recommended by Lyonet, or spirits of
wine or of turpentine; and it is often useful to let _larvæ_ remain
a few days in the latter, by which means the vessels become firmer
and stronger. The parts of _pupæ_ become much more distinct if they
are boiled for a few minutes: and the same mode may be adopted in the
examination of spiders.
The most convenient mode of proceeding, which was that also of
Lyonet, is to dissect the insect in water, or, to avoid putridity,
in diluted spirits,--if small, upon a concave glass, to which it
should be fastened by means of a little melted wax; if larger, in
the bottom of a common chip box, surrounded with a border of wax to
retain the fluid. The integuments of the insect, being carefully
divided longitudinally with scissors, should if flexible be turned
back, and fixed by small pins stuck in by a fine pair of pliers,
while the skin at the same time is stretched by another. After
making such observations as present themselves without further
dissection, the viscera must be cautiously extracted, washing away
the fat which surrounds them with spirits of turpentine, in which it
is soluble, applied by camel's-hair pencils. After separation they
may conveniently be examined by putting them into water, and gently
shaking them so as to cause the parts to unfold. If endowed with the
patience of Swammerdam, you may even arrive at injecting these minute
parts with wax or coloured fluids, conveyed by delicate glass tubes
having one end as fine as a hair, which he also employed to fill
the viscera with air; and afterwards drying them in the shade, and
anointing them with oil of spike in which a little resin had been
dissolved, he succeeded in preserving them. If it is not convenient
to finish the dissection of an insect at once, it should be covered
with spirits of wine. Swammerdam found a mixture of spirits and
distilled vinegar very useful for keeping caterpillars previously to
dissecting them, as it consolidated the parts[917].
* * * * *
And now having brought to a close my long wanderings in this ample
and intricate field, and having threaded, as well as my slender
powers and limited knowledge enabled me, the infinite turnings
and convolutions of this Dædalean labyrinth--the _Anatomy_ and
_Physiology_ of insects,--will you not own that the volume of wonders
I have laid before you proves irrefragably that, though these minims
of nature apparently rank so low in the scale of being, yet in their
structure, instead of being, as might be expected, more simple,
they are infinitely more complex and highly wrought than those
animals that are placed the nearest to ourselves? the CREATOR in the
latter doing every thing by a beautiful _simplicity_; while in the
former, the more to magnify his power and skill, because they afford
no apparent space for it, by a wonderfully curious and intricate
_multiplicity_: and whether we study the one or the other, we shall
in both trace the footsteps of that adorable LOVE which has shown
attention to the comfort and well-being of the lowest insect, as well
as of the highest of his creatures.
I am, &c.
FOOTNOTES:
[801] VOL. II. LETTER XXII. VOL. III. LETTERS XXXIV.-XXXVI.
[802] VOL. II. p. 280, 295--, 306, 310--. &c.
[803] _Philos. Trans._ 1818. 174. _t._ viii. _f._ 4-6.
[804] See above, p. 150--.
[805] _Schmetterl._ 105.
[806] _Philos. Trans._ 1819. 172, 174, 187.
[807] _Anat. Comp._ i. 90.
[808] _Philos. Trans._ 1819. 175.
[809] Cuv. _ubi supr._ 90--.
[810] Cuv. _Ibid._ i. 89--.
[811] See above, p. 85.
[812] Lyonet _Anat._ _t._ iv. _f._ 3.
[813] _Ibid._ 93--.
[814] Cuv. _Anat. Comp._ i. 134.
[815] Chabrier _Sur le Vol des Ins._ c. i. 445.
[816] PLATE XXI. FIG. 6. _a._
[817] De Geer iv. _t._ xv. _f._ 11. _m n, o p._
[818] Lyonet _Anat._ 93.
[819] Lyonet _Anat._ _t._ xiii. _f._ 1, 2.
[820] Ramdohr _Anat._ _t._ v. _f._ 1. _e._ _f._ 3.
[821] Chabr. _ubi supr._ 440--.
[822] _Ibid._ 442, &c.
[823] _N. Dict. d'Hist. Nat._ xxii. 80.
[824] VOL. III. p. 663, 670. See above p. 21.
[825] Chabrier _Sur le Vol des Ins._ c. i. 446.
[826] VOL. III. p. 411.
[827] _Ubi supr._ 437, 439.
[828] PLATE XXII. FIG. 11, 12. c. Chabrier _ubi supr._ c. iii. _t._
xi. viii. _f._ 9. S. D. _i, k._ c. i. 440--.
[829] PLATE XXII. FIG. 11, 12. c. Chabrier _Sur le Vol des Ins._ c.
iii. _t._ xi. viii. _f._ 9. S. D. _i, k._ c. i. 440--.
[830] Cuv. _Anat. Comp._ i. 94--.
[831] _N. Dict. d'Hist. Nat._ xxii. 80.
[832] _Ubi supr._ 101--.
[833] VOL. I. p. 67.
[834] _Anat. Comp._ i. 432--.
[835] _Anat._ _t._ vii. _f._ 2. left hand.
[836] _Ibid._ right hand.
[837] _Ibid._ 115--.
[838] Cuv. _ubi supr._
[839] VOL. III. p. 135--.
[840] _Anat. Comp._ i. 447.
[841] VOL. III. p. 366. PLATE XXVII. FIG. 1, 4. n´.
[842] Ibid. FIG. 3. n´.
[843] PLATE XXVII. FIG. 1. _a._
[844] VOL. III. p. 367--, 541, 584. PLATE XXII. FIG. 7. Cuv.
_ubi supr._ 448.
[845] PLATE XXVII. FIG. 5. _a._
[846] _Anat. Comp._ i. 136.
[847] De Geer iv. _t._ xv. _f._ 11. _o, p._
[848] Marcel de Serres _Comparaison, &c._ 3--.
[849] _Ibid._ 4.
[850] _Ibid._ 5.
[851] PLATE XXII. FIG. 11. _h´_.
[852] VOL. III. p. 579.
[853] PLATE XXII. FIG. 6. VOL. III. p. 585--.
[854] Cuv. _Anat. Comp._ i. 436. PLATE XXI. FIG. 6.
[855] Ibid. _a, b._ Lyonet _Anat._ 37.
[856] Cuv. _ubi supr._ 458--. VOL. III. p. 368, 378, 382.
[857] Cuv. _ubi supr._ 459.
[858] Chabr. _Sur le Vol des Ins._ c. i. 441.
[859] Chabr. _Sur le Vol des Ins._ c. i. 415.
[860] _Ibid._
[861] _Ibid._ c. iii. 344. _t._ viii. _f._ 8, 9.
[862] _Ibid._ c. i. 440.
[863] _Ibid._ 444.
[864] _Ibid._ 445. c. iii. 359.
[865] _Ibid._ c. ii. 332. c. iii. 359.
[866] _Ibid._ c. i. 445.
[867] _Ibid._ c. iv. 78.
[868] Chabr. _Sur le Vol des Ins._ c. i. 415, 442. c. iv. 80.
[869] _Ibid._ c. i. 442.
[870] _Ibid._ 439--.
[871] Chabrier _Analyse_, 28. The latter part of this passage is
copied from a MS. note of the author's in my copy.--W. K.
[872] Chabrier _Analyse_, Ibid. _Sur le Vol des Ins._ c. i. 445. VOL.
III. p. 617.
[873] _Analyse_ ubi supr.
[874] _Sur le Vol des Ins._ c. i. 448, c. ii. 336.
[875] VOL. III. p. 579.--
[876] Chabr. _Ibid._ c. i. 443. ii. 316, 332.
[877] Chabr. _Sur le Vol des Ins._ c. ii. 333.
[878] _Ibid._ 332. PLATE XXII. FIG. 11, 12. c. A cupuliform process
is also observable at the side of the metaphragm. Ibid. FIG. 10. a.
[879] Chabr. _Ibid._ c. iv. _t._ xi.-4. _f._ 14.
[880] _Ibid._ c. i. 445. xi.-8. _f._ 8, 9.
[881] Chabr. _Sur le Vol des Ins._ c. ii. 336. note 1. VOL. III. p.
292--.
[882] Chabr. _Ibid._ c. i. 447.
[883] See above, p. 66--.
[884] See above, p. 73--.
[885] Chabrier _Sur le Vol des Ins._ c. i. _Addend._ 298.
[886] See above, p. 178--.
[887] VOL. III. p. 700--.
[888] Chabr. _ubi supr._ c. i. 422.
[889] Cuv. _Anat. Comp._ i. 451.
[890] Chabr. _Analyse_ 25. _Sur le Vol des Ins._ c. i. 423, 452.
_Addend._ 301.
[891] See above, p. 83.
[892] Lyonet _Anat._ _t._ xiii. _f._ 1, 2.
[893] Lyonet _Anat._ _t._ xiii. 188--, 584.
[894] _Ibid._ 189.
[895] _N. Dict. d'Hist. Nat._ xxx. 421.
[896] _Arachnid._ 9. _t._ i. _f._ 7. _r._
[897] _Ibid._ _o._
[898] _Ibid._ 10.
[899] _Arachnid._ 45. _t._ iii. _f._ 31. _m, n, q, r, t._
[900] VOL. II. p. 309--.
[901] Mouffet _Theatr._ 275.
[902] _N. Dict. d'Hist. Nat._ xxviii. 249.
[903] _Phil. Acc. of Works of Nat._ 144.
[904] Clark in _Linn. Trans._ iii. 309.
[905] _Fn. Suec._ 1799.
[906] _Anatomy of Expression in Painting_, 170.
[907] Bonnet _Œuvr._ ii. 124.
[908] _N. Dict. d'Hist. Nat._ xxii. 81.
[909] 1 Cor. xv. 50--.
[910] _N. Dict. d'Hist. Nat._ ubi. supr.
[911] Swamm. _Bibl. Nat._ _t._ xviii. _f._ 2. _l, m, n, o._ Reaum. v.
_t._ xxix. _f._ 7. _m, n, o, p, q._
[912] VOL. II. LETTER XXVI.
[913] _De Bombyc._ 5.
[914] Reaum. ii. 185--.
[915] VOL. II. p. 186.
[916] _t._ vi. _f._ 3.
[917] These directions for dissecting are chiefly taken from
Swammerdam, _Life_ xiv.-- and Lyonet _Anat._ 7--.
LETTER XLIV.
_DISEASES OF INSECTS._
Having laid before you what observations I thought might sufficiently
explain all the principal features of the Anatomy of insects both
external and internal, you will next expect to be informed whether,
like the higher animals, they are subject to have the admirable order
observable in their frame interrupted by _Disease_; and you will
perhaps imagine, from the multiplicity of their organs and vessels,
that they must be peculiarly exposed to derangements of the vital
and other functions. That they have their diseases is certain; but,
except in the case of their appropriate parasitic assailants, which
is a part of their economy, it does not appear that their maladies
are more numerous and frequent than those of other animals. The
same ALMIGHTY POWER which endowed them with so complex a structure,
generally upholds them in health during their destined career, until
they have fulfilled the purpose of their creation, when _they die and
return again to their dust_[918].
But perhaps I may seem to you as making too great a parade about
these little insignificant creatures if I assign a separate letter
to the consideration of their _diseases_: but when you recollect
that Aristotle has a chapter on this subject[919], and that the
learned Willdenow has devoted a distinct portion of his excellent
introductory work on Botany to the diseases of Plants[920],--you will
perhaps be of a different mind: indeed, some facts I shall have to
communicate are so remarkable and interesting, that I am sure, when
you have read this letter, you will not think the subject one that
deserves to be slighted.