release of the perfect insect from its cocoon is effected--that,
namely, wherein its own exertions chiefly accomplish the work. I
shall from a large number select only a few instances. The texture
of the cocoon of the silkworm-moth is uniform in every part, and the
layers of silk are equally thick at both ends. The moth makes its
way out by cutting or breaking these threads at the end opposite
to its head: an operation which, as it destroys the continuity of
the silk, those who breed these insects are particularly careful
to guard against, by exposing the cocoon to heat sufficient to
destroy the included pupa. The question is--What instruments does
the moth employ to effect this? And this we are not able to answer
satisfactorily. Malpighi asserts that the animal first wets the
silk with a liquid calculated to dissolve the gum that connects the
threads, and then employs its lengthened head to push them aside and
make an opening[668]. But, as Reaumur has observed, besides that
so obtuse a part as the head of a moth is but ill fitted to act as
a wedge, we find the threads not merely pushed to each side, but
actually cut asunder. He therefore infers that the eyes, which are
the only hard organs of the head, are the instruments by which the
threads are divided--their numerous minute facets serving the purpose
of a fine file[669]. It should be observed, however, that Mr. Swayne
confirms Malpighi's assertion, that the silkworm does not cut, but
merely pushes aside, the threads of its cocoon; and he informs us
that he has proved the fact, by unwinding a pierced cocoon, the
thread of which was entire[670]. Yet Reaumur's correctness cannot be
suspected: and he affirms, that from observation there can scarcely
be a doubt that most of the threads are broken[671]; which is further
confirmed in an account of the breeding of silk-worms published in
the _American Philosophical Transactions_: in which it is expressly
stated, that cocoons out of which the fly has escaped, cannot be
wound[672]. Analogy, it must be confessed, is against Reaumur's
opinion; since other kinds of silkworms make their escape by means
of a _fluid_. Thus we are informed by Dr. Roxburgh, that _Attacus
Paphia_, when prepared to assume the imago, discharges from its
mouth a large quantity of liquid, with which the upper end of the
case is so perfectly softened, as to enable the moth to work its way
out in a very short space of time,--an operation which, he says, is
always performed in the night[673]. Perhaps the two opinions may be
reconciled, by supposing the silkworm first to moisten and then break
the threads of its cocoon. In those that are of a slighter texture,
a mere push against the moistened end is probably sufficient: and
hence we find in so many newly disclosed moths the hair in that part
wet, and closely pressed down[674]. If it be apparently difficult
for the silkworm-moth to effect an opening in its cocoon, how much
harder must seem the task of the puss-moth (_Cerura Vinula_) to
pierce the solid walls of its wood-thickened case? Here the eyes
are clearly incompetent; nor could any ordinary fluid assist their
operation, for the gum which unites the ligneous particles is
indissoluble in _aqueous_ menstrua. You begin to tremble for the
fate of the moth incarcerated in such an impervious dungeon--but
without cause: what an _aqueous_ solvent cannot effect, an _acid_ is
competent to: and with a bag of such acid our moth is furnished. The
contents of this she pours out as soon as she has forced her head
through the skin of the chrysalis, and upon the opposite end of the
cocoon. The acid instantly acts upon the gum, loosens the cohesion
of the grains of wood, and a very gentle effort suffices to push
down what was a minute ago so strong a barrier. How admirable and
effectual a provision! But there is yet another marvel connected
with it. Ask a chemist, of what materials a vessel ought to be to
contain so potent an acid: he will reply,--of glass. Yet our moth
has no glass recipient: her bottle is a membranous bag; but of so
wonderful a fabric as not to be acted upon by a menstruum which a
gum, apparently of a resinous nature, is unable to resist! This fact
can only be explained by the analogous insensibility of the stomach
to the gastric juice, which in some animals can dissolve bone,--and
it is equally worthy of admiration. In both cases, the vitality of
the membranous or fleshy receptacle secures it from the action of the
included fluid; but _how_--who shall explain?
Ordinarily it is the moth that breaks the cocoon; but in the goat-moth
and many _Tortrices_ it is the pupa itself that performs the work,
either wholly or partially. The pupa of the former is for this purpose
furnished with sharp points upon the head, capable of effecting this
object[675]. The locust-moth, another species of _Cossus_ (_C. Robiniæ_
Peck), whose history has been admirably detailed by Professor Peck,
has a different process. "In the silk-moth," says he, "and all others
which I have had opportunity to observe, the chrysalis bursts _in_ the
cocoon, and the fluid which surrounded the new insect in it escaping
at the same time, so weakens or dissolves the fibre and texture of
the silk, that the moth is able to extricate itself, leaving the
chrysalis behind it; but this is not the manner in the locust-moth.
After remaining till all its parts are fully grown and it is ready to
quit its prison, a certain quantity of exercise is necessary, to break
the ligaments which attach the moth to the shell of the chrysalis, and
to loosen the folds of the abdomen. In taking this exercise, it can
only move the abdomen in various directions: as one side of the rings
is moved forward, the hooks in the serrated lines above mentioned (the
_adminicula_) take hold of the silk, and prevent their sliding back;
the next flexure brings forward the opposite side of the rings, which
are prevented by the points on that side from slipping back in the
same manner, and the chrysalis is forced out of the slightly woven
extremity of the cocoon, and through the silk-lined cavity, till it is
protruded for about one-third of its length out of the opening in the
bark, and into the air[676]."
An exception to the general rule--that the rupturing of the cocoon is
the business of the inclosed insect itself--is met with amongst ants;
the workers of which not only feed the young, but actually make an
aperture in their cocoons, cutting the threads with their mandibles
with admirable dexterity and patience, one by one, at the time they
are ready to emerge, the precise period for which these indefatigable
nurses are well aware of, that they may meet with no obstacle. Without
this aid, the young ant would be unable to force its way through the
strong and dense coating of silk that infolds it[677]. And a proceeding
somewhat akin to this was observed by the Hon. Captain Percy, R.N., who
himself related it to me. Being fond of the study of insects, he was
in the habit of attending to their motions; and in the beginning of
September 1821 noticed those of a number of female _Tipulæ_, probably
_T. oleracea_ L., busily engaged in depositing their eggs amongst the
roots of grass. While observing these proceedings, he at the same time
saw one quitting its pupa-case, which had already by its own efforts
got its head, thorax, and anterior legs out of it. It was then joined
by two _male_ flies; which, with their anal forceps and posterior legs
taking hold of the pupa-case, appeared with their mouths and anterior
legs to push the little prisoner upwards, moving her backwards and
forwards; and as they kept raising her, shifting their hold of the
skin till she was entirely extricated, when they left her to recover
her strength by herself. Probably the extreme length of the two pair
of hind-legs of these animals may render such assistance necessary for
their extrication.
There remains yet to be explained under this head the manner in
which the perfect insect is excluded from certain aquatic pupæ; such
as those of _Phryganeæ_, gnats, and one of those _Tipulidæ_ that
resemble gnats. These pupæ (perhaps that they may be safe from the
attack of birds) are destined to remain during the greater part of
their existence in this state at the bottom of the water. But it is
obvious that if the perfect insects were there to be disclosed, their
wings would be wetted, and they would be drowned. It is the provision
by which this result is obviated that now calls for your attention.
You have already been told that the larvæ of _Phryganeæ_ inclose
themselves in cases of different materials, open at each end[678]. You
have also learned, that in becoming pupæ, they secure each end of their
cases with a grating of silk[679]. When that change has occurred, they
remain motionless at the bottom of the water. Now how are these pupæ,
encased in tubes of a greater specific gravity than the surrounding
fluid, to make their way to the surface when the time has arrived
for their becoming denizens of the air? This they accomplish in the
following manner:--The pupa is furnished with two strong exterior
moveable mandibuliform processes, and has the power of moving its four
anterior legs and antennæ while in the pupa-case. With these temporary
_jaws_ it makes an opening in one of the silken doors of its case,
forces its way out at that end, and then by moving its legs, the cases
of which in some species are ciliated for this very purpose, swims to
the surface, where its skin splits, and discloses the included insect.
That these jaws are given for the express and exclusive purpose of
being thus applied, seems undeniable. The pupa eats nothing--they are
therefore in every other point of view superfluous. They are given to
it alone of all other similar pupæ, because unnecessary to all others;
and they are cast off along with the rest of the puparium, the perfect
insect having no vestige of jaws[680].
The _gnat_ has to undergo its change on the surface of the water--How
is it to accomplish this without being wetted? In the pupa state
they usually remain suspended with the posterior end of the body
turned downwards: but when the period for its change is arrived,
it stretches it out upon the surface, above which its thorax is
elevated. Scarcely has it been a moment in this position, than,
swelling out the interior and anterior parts of the thorax, it
causes it to split between the two respiratory horns. Through this
opening the anterior part of the gnat then emerges. As soon as the
head and trunk are disengaged, it proceeds with its labour, and gets
out more and more; elevating itself so as to appear in the puparium
like a mast in a boat. As it proceeds, the mast is more and more
elevated and lengthened, till it becomes nearly perpendicular--just
as the mast of a boat is gradually raised from a nearly horizontal
to a vertical position: at this period a very small portion of the
abdomen remains in the puparium. Neither its legs nor wings are of
any use in maintaining it in this position. The latter are too soft,
and, as it were, folded; and the former are stretched out along
the abdomen--the segments of this last part are the only agents.
The observer who sees how the little boat gradually sinks, and how
its margin approaches the water, forgets the mischievous insect it
contains, which at another time he would crush without remorse, and
becomes interested for its fate; especially should wind agitate the
water. A very little is sufficient to drive about rapidly the little
voyager, since it catches the wind in some degree as a sail. If it
should be upset, it would be all over with it;--and numbers do thus
perish. The gnat, after having fixed itself thus perpendicularly,
draws first its two anterior legs out of their case, and moves them
forward, and next the two intermediate ones; then inclining itself
towards the water, it rests its legs upon it, for water is to them a
soil sufficiently firm and solid to support them, although surcharged
with the weight of the insect's body. As soon as it is thus upon the
water, it is in safety; its wings unfold themselves and are dried,
and it flies away. All this is the work of an instant[681].
The pupæ of _Chironomus plumosus_ proceed from those red worm-like
larvæ so common throughout the summer in tubs of rain-water, &c.,
described by Reaumur[682]. They are not inclosed in cases, but are of
a greater specific gravity than the water at the bottom of which they
reside, until within a few hours of the exclusion of the fly. They have
the power of swimming, however; and by moving the tail alternately
backwards and forwards, can slowly raise themselves to the top of
the water. But here occurs a difficulty. For the extrication of the
imago it is necessary that they should remain quietly suspended at
the surface; and moreover that the thorax, in which the opening for
its exit is to be made, should be at least level with it: and this is
precisely what takes place. If you watch one of these pupæ when it
ascends from the bottom, you will see that as soon as it has reached
the top it remains suspended there motionless; and that its thorax
is the highest part of the body, and level with the surface. Now the
question is, in what way this is accomplished? How can a pupa of
greater specific gravity than water, remain suspended without motion at
its surface? and how can its thorax, which is at its heaviest end, be
kept uppermost?--By a most singular and beautiful contrivance, which I
shall explain; the more particularly because it has escaped Reaumur,
and, as far as I know, all other entomological observers. The middle of
the back of the thorax has the property of repelling water--apparently
from being covered with some oily secretion. Hence, as soon as the pupa
has once forced this part of its body above the surface, the water is
seen to retreat from it on all sides, leaving an oval space in the
disk, which is quite dry. Now though the specific gravity of the pupa
is greater than that of water, it is but so very slightly greater, that
the mere attraction of the air to the dry part of the thorax, when once
exposed to it, is sufficient to retain it at the surface; just as a
small dry needle swims under similar circumstances. That this is a true
solution of the phænomenon, I am convinced by the result of several
experiments. If, when the pupa is suspended at the surface, a drop of
water be let fall upon the dry portion of the thorax, it instantly
sinks to the bottom,--the thorax, which belongs to the heaviest half,
being the lowest; and if the pupa be again brought to the surface, so
that the fluid is repelled from its disk, it remains suspended there
without effort, as before. Just previously to the exclusion of the fly,
the dry part of the thorax is seen to split in the middle. The air
enters, and forms a brilliant stratum resembling quicksilver, between
the body of the insect and its puparium; and the former pushing forth
its head and forelegs, like the gnat, rests the latter upon the water,
and in a few seconds extricates itself wholly from its envelope.
Before I close this letter, I must state a fact connected with the
subject of it that deserves to be recorded. It is a general rule,
that _one_ pupa-case incloses only _one_ insect; but Kleesius, a
German entomologist, asserts that he had once _two_ specimens of
_Gastropacha quercifolia_ produced from _one_ pupa; which was large,
being full two inches long, and one thick.
FOOTNOTES:
[562] In the _Hemiptera_ the male _Cocci_ (Reaum. iv. 32.) and
_Aleyrodes_ (Ibid. ii. 311.) belong to the second division.
[563] The terms _larva_ and _pupa_, applied to the insects of this
subdivision, are perhaps not strictly proper.
[564] The larvæ and pupæ of many of the _homopterous_ section of
_Hemiptera_ differ often from the imago, not only in their fore-legs
(PLATE XVI. FIG. 4.), but also in other respects. I have the larva of
a _Centrotus_ from Canada, given me by Dr. Bigsby, which has a long
anal process or tail.
[565] See above, p. 125--.
[566] iii. 135.
[567] The pupæ of _Cassida_, _Imatidium_, &c. seem to vary somewhat
from this type, the upper part being neither membranous nor
exhibiting distinctly the form of the inclosed imago.
[568] The following arrangement of pupæ is perhaps in some respects
better than that above given. But it is scarcely possible to propose
one free from objections.
I. Capable of eating and walking.
i. Like the perfect insect, except in proportion and number of
parts.
1. Except in proportion (_Lice_, _Poduræ_, _Mites_,
_Spiders_, _Scorpions_, &c).
2. Except in proportion and number (_Centipedes_,
_Millepedes_).
ii. With rudiments of the organs of flight.
1. With oral organs resembling those of the perfect insect
(_Hemiptera_).
2. With oral organs differing from those of the perfect
insect (_Libellula_ L., _Ephemera_ L.).
II. Incapable of eating and walking.
i. Incomplete pupæ.
ii. Obtected.
iii. Coarctate.
Lamarck divides the pupæ of insects that undergo a metamorphosis into
three kinds, which he names--_Chrysalis_, _Mumia_, and _Nympha_.
i. _Chrysalis._ Under this denomination he includes all inactive pupæ
inclosed in an opaque puparium which entirely conceals them. These he
further subdivides into two kinds.
1. _Chrysalis signata._ This term is synonymous with the _Pupa
obtecta_ of Linné, or the _Chrysalis_ of _Lepidoptera_ and some
_Diptera_.
2. _Chrysalis dolioloides._ Equivalent to the _Pupa coarctata_ Linn.
peculiar to those _Diptera_ that assume this state in the skin of the
larva.
ii. _Mumia._ All inactive pupæ which are covered by a transparent
skin, through which all the parts of the inclosed imago may be seen,
subdivided also into two.
1. _Mumia coarctata._ Corresponding with the _Pupa incompleta_ Linn.,
which includes the _Coleoptera_ and most of the _Hymenoptera_.
2. _Mumia pseudonympha_, confined to the Pupa of _Phryganea_ and some
others. This might be named _Pupa subincompleta_.
iii. _Nympha._ Under this denomination are included all insects that
undergo only a partial metamorphosis, and are active in their pupa
state, corresponding with the _Pupa semicompleta_ Linn. and also
_subsemicompleta_ MacLeay. See _Anim. sans Vertebr._ iii. 285--.
M. Latreille has started an ingenious idea on this subject with
regard to these kinds of metamorphosis, which comprehends both larva
and pupa under a distinct denomination: as thus--
1. _Demilarve_ and _Deminymph_, synonymous with the _Semicomplete
Metamorphosis_. 2. _Larve_ and _Nymph_, answering to _Incomplete
Metamorphosis_. 3. _Caterpillar_ and _Chrysalis_, answering to
_Obtected Metamorphosis_. 4. _Vermilarve_ and _Pupa_, answering to
_Coarctate Metamorphosis_. _N. Dict. d'Hist. Nat._ xvi. 272.
[569] _N. Dict. d'Hist. Nat._ vii. 57.
[570] De Geer ii. 105.
[571] Reaum. ii. 428--.
[572] Swamm. _Bibl. Nat._ Engl. Tr. ii. 32. _t._ xli. _f._ 2. Comp.
Reaum. iv. _t._ xxv. _f._ 1.
[573] _Ibid._ i. 144.
[574] Reaum. i. 355.
[575] _N. Dict. d'Hist. Nat._ ubi sup. 59.
[576] PLATE XVI. FIG. 14. _N. Dict. d'Hist. Nat._ vii. 59.
[577] _Ins. Surinam._ _t._ xliv.
[578] De Geer v. 47. _t._ ii. _f._ 29-31.
[579] In the pupa of _Hydrophilus piccus_ (Lesser L. _t._ ii. _f._
13, 14), the arrangement of the parts is nearly the same, but the
tarsi are not reflexed.
[580] _Ibid._ _f._ 9, 10. De Geer ii. _t._ xxxii. _f._ 5. Reaum. v.
_t._ xxxvi. _f._ 14.
[581] Reaum. _Ibid._ _t._ ii. _f._ 9.
[582] The legs of _Tipula replicata_ L. are placed in a similar way.
De Geer vi. _t._ xx. _f._ 12. _l._
[583] Rös _t._ 81.
[584] _Ibid._ _t._ 95.
[585] De Geer vi. 237. _t._ xiv. _f._ 8.
[586] Reaum. v. _t._ ii. _f._ 7. The anal and ventral spines of
_Tipula replicata_ are also remarkable. De Geer vi. _t._ xx. _f._ 14.
[587] De Geer _Ibid._ 377. _t._ xxiii. _f._ 8, 9. _n._ Reaum. v. 42.
_t._ vi. _f._ 9. _m n._
[588] The caterpillar consists of twelve segments (Lyonnet _t._ i.
_f._ 4, 5), excluding the head; on each of which, except the 2d,
3d, and 12th, there is a pair of spiracles. The chrysalis usually
exhibits an analogy to this structure, though the first, second, and
last pair of spiracles are more or less obsolete in most.
[589] De Geer ii. 847. _t._ xxix. _f._ 7. _a b._
[590] _Animaux sans Vertebres_, iii. 287.
[591] _N. Dict. d'Hist. Nat._ vii. 57.
[592] Sepp ii. _t._ i. _f._ 4. _t._ ii. _f._ 4. _t._ iv. _f._ 5.
[593] PLATE XVI. FIG. 12.
[594] PLATE XVI. FIG. 10.
[595] _Ins. Surinam. t._ lx. It is singular that the chrysalis of its
congener, _Morpho Teucer_, which she figures _t._ xxiii., exhibits no
such process. The larvæ also widely differ.
[596] PLATE XVI. FIG. 11.
[597] Sepp ii. _t._ iii. _f._ 5.
[598] Sepp i. _t._ vii. _f._ 5.
[599] _De Insectis_, ed. Lister. _t._ 1.
[600] _Ins. Surinam. t._ liii.
[601] Sepp i. _t._ ii. _f._ 6.
[602] _N. Dict. d'Hist. Nat._ vii. 60.
[603] _Ibid._ 57.
[604] See above, VOL. I. p. 131.
[605] Reaum. ii. 158. _t_. viii. _f_. 4, 5.
[606] Lesser L. i. 160. note. _t._ ii. _f._ 19.
[607] _N. Dict. d'Hist. Nat._ xxvi. 165. Reaum. i. 347. Rösel says
this is present only in some individuals. I. ii. 47.
[608] PLATE XVI. FIG. 13. _a._
[609] _Ins. Surinam. t._ iii.
[610] De Geer ii. 433. _t._ viii. _f._ 4. _t._
[611] See above, VOL. II. p. 300.
[612] This description was taken from a _puparium_ in my own cabinet;
it is similarly described by De Geer i. 490. _t._ vii. _f._ 2.
[613] PLATE XXIII. FIG. 8, 9.
[614] _Kliemann Beitrage_, 304.
[615] See above, VOL. I. 464.
[616] Von Scheven in _Naturf._ stk. xx. 64. _t._ ii. _f._ 4.
[617] PLATE XVII. FIG. 2. Lesser L. _t._ ii. _f._ 26.
[618] PLATE XVII. FIG. 1. Lesser L. _t._ ii. _f._ 24, 25.
[619] Whether M. Meigen has separated this fly generically from others,
I am not aware: in my catalogue it stands under the name of _Tyrophaga_.
[620] Reaum. iii. 376. _t._ xxxi. _f._ 7.
[621] Ibid. iv. 318. _t._ xxiii. _f._ 1-4. xxv. _f._ 1.
[622] _Ins. Surinam._ _t._ xxix.
[623] _Ins. Surinam._ _t._ xxxii. Lister imitated the gilding of
_Chrysalises_ by putting a small piece of a black gall in a strong
decoction of nettles: this produced a scum, which when left on
cup-paper, he says, will exquisitely gild it.--Ray's _Letters_, 87. 90.
[624] _Beitrage_, 181.
[625] Sepp. pt. ii. _t._ ii. _f._ 4.
[626] Rösel. I. i. 61. ii. 5.
[627] Reaum. i. 383.
[628] Lister's _Goedart_. 122.
[629] Reaum. ii. 10--.
[630] Ibid. 24.
[631] This is a legend of Virgil, of which an account is given in
_The Lay of the Last Minstrel_, Note xv. 12mo ed. 1822, p. 257.
[632] Haworth _Lepidopt. Britann._ i. 125. An instance is recorded
in Scriba's Journal, in which a pupa was not disclosed until the
_fourth_ year. B. i. st. iii. 222. Pezold. 170.
[633] Marsham in _Linn. Trans._ x. 402.
[634] Meinecken found, that of several pupæ of _Saturnia pavonia_,
some kept all winter in a room heated daily by a stove, and others
in a cold chamber, some of both parcels appeared in March (none
earlier), and some of both had not appeared in July, though evidently
healthy. _Naturf._ viii. 143.
[635] The exclusion of certain moths, &c. from the pupa is probably
regulated by the time their eggs require to be hatched, and the
appearance of the leaves that constitute their appropriate food.
[636] Mr. Marsham makes a similar observation in _Linn. Trans._, ubi
supr.
[637] See above, p. 245.
[638] The appearance of them sometimes continues to near the end of the
month: it began on the 19th, when Reaumur observed them. vi. 480. 488.
[639] _Bibl. Nat._ E. Transl. i. 103--.
[640] Reaum. vi. 486.
[641] Brahm. 423. 421.
[642] _Naturf._ xxi. 75.
[643] Reaum. ii. 423.
[644] De Geer ii. 370. It is not certain, however, that De Geer did
not, in this instance, mistake the winter habitation of a larva for
a cocoon intended to shelter the future chrysalis; since Lyonnet
informs us that they spin a habitation to pass the winter in. _Traité
Anatomique_, &c. 9.
[645] De Geer i. 490. _t._ vii. _f._ 3, 4.
[646] _Œuv._ ii. 1.
[647] De Geer v. 229.
[648] VOL. II. 300--.
[649] VOL. II. 298--.
[650] I. iv. 101.
[651] Reaum. vi. 407.
[652] Haworth _Lepidopt. Britann._ i. 127.
[653] De Geer ii. 566.
[654] Reaum. iii. _t._ xlv. _f._ 12-14.
[655] For this whole account, see Reaum. iv. Mem. viii.
[656] Ibid. 472.
[657] See above, p. 255--. and VOL. II. p. 301--.
[658] Bonnet, _Œuv._ ii. 169.
[659] Bonnet, _Œuvr._ ii. 207.
[660] Rös. I. iv. 209. _t._ lxiii. ccxii.
[661] See above, p. 217.
[662] Bonnet, _Œuvr._ ii. 229.
[663] De Geer ii. 477.
[664] Sepp. iv. _t._ xi. _f._ 8.
[665] PLATE XVII. FIG. 5. N.B. Sepp's figure represents the
_exterior_ funnel; and this, which exhibits the cocoon divided
longitudinally, the _interior_ one, or dome.
[666] Rös. I. iv. 31.
[667] _Naturf._ viii. 133.
[668] _De Bombyc._ 29.
[669] Reaum. i. 624.
[670] _Trans. of the Society of Arts_, vii. 131.
[671] Reaum. _ubi supr._
[672] ii. 359.
[673] _Linn. Trans._ vii. 35.
[674] Pezold. 171.
[675] Lyonnet 16.
[676] _Some Notice of the Insect which destroys the Locust-trees_,
70. This Memoir is in some American periodical work, of which I have
not the title.
[677] Huber _Fourmis_ 82.
[678] VOL. I. p. 467.
[679] VOL. II. p. 264.
[680] De Geer ii. 519.
[681] Reaum. iv. 610--.
[682] Ibid. v. 30--. _t._ v. _f._ 1-10. See above, p. 153--.
LETTER XXXII.
_STATES OF INSECTS._
IMAGO STATE.