Barton doubts whether the flowers that catch insects, being only
temporary organs, can derive any nutriment from them; and he does not
think it probable that the leaves of _Dionæa_, &c., which are usually
found in rich boggy soil, can have any need of additional stimulus.
As nothing however is made in vain, there can be little doubt that
these ensnared insects are subservient to some important purpose
in the economy of the plants which are endowed with the faculty of
taking them, though we may be ignorant what that purpose is; and an
experiment of Mr. Knight's, nurseryman in King's Road, London, seems
to prove that in the case of Dionæa, at least, the very end in view,
contrary to Dr. Barton's supposition, is the supplying the leaves
with animal manure; for he found that a plant upon whose leaves he
laid fine filaments of raw beef, was much more luxuriant in its
growth than others not so treated[531]. Possibly the air evolved from
the putrefying insects with which _Sarracenia purpurea_ is sometimes
so filled as to scent the atmosphere round it, may be in a similar
manner favourable to its vegetation.
Most of the insects which are found in the tubular leaves of this
and similar plants enter into them voluntarily; but Sir James Smith
mentions a curious fact, from which it appears that in some cases
they are deposited by other species. One of the gardeners of the
Liverpool Botanic Garden observed an insect, from the description
one of the _Crabronidæ_, which dragged several large flies to the
_Sarracenia adunca_, and, having with some difficulty forced them
under the lid or cover of its leaf, deposited them in its tubular
part which was half filled with water: and on examination all the
leaves were found crowded with dead or drowning flies[532]. What was
the object of this singular manœuvre does not seem very obvious. At
the first glance one might suppose that, having deposited an egg in
the fly, it intended to avail itself of the tube of the leaf instead
of a burrow. Yet we know of no such strange deviation from natural
instinct, which would be the more remarkable because the insect was
_European_, while the plant was American and growing in a hot-house.
And at any rate it does not seem very likely that the insect would
commit her egg to the tube without having previously examined it;
in which case she must have discovered it to be half full of water,
and consequently unfit for her purpose.--It is not so wonderful that
many large flies should, as Professor Barton informs us, drop their
eggs into the Ascidia furnished with dead carcases: and it seems
very probable that Dytisci oviposit in them; for the Squilla which
Rumphius found there was probably one of their larvæ, this being the
old name for them[533].
However problematical the agency of insects caught by plants as to
their _nutriment_, there can be no doubt that many species perform
an important function with regard to their _impregnation_, which
indeed without their aid would in some cases never take place at all.
Thus, for the due fertilization of the common Barberry (_Berberis
vulgaris_) it is necessary that the irritable stamens should be
brought into contact with the pistil by the application of some
stimulus to the base of the filament; but this would never take place
were not insects attracted by the melliferous glands of the flower to
insinuate themselves amongst the filaments, and thus, while seeking
their own food, unknowingly fulfill the intentions of nature in
another department[534].
The agency of these little operators is not less indispensable in the
beautiful tribe of _Iris_. In these, as appears from the observations
of Kölreuter, the true stigma is situated on the upper side of a
transverse membrane (_arcus eminens_ of Haller) which is stretched
across the middle of the under surface of the petal-like expansion or
style-flag, the whole of which has been often improperly regarded as
fulfilling the office of a stigma. Now as the anther is situated at the
base of the style-flag which covers it, at a considerable distance from
the stigma, and at the same time cut off from all access to it, by the
intervening barrier formed by the _arcus eminens_, it is clear that
but for some extraneous agency the pollen could never possibly arrive
at the place of its destination. In this case the _humble-bee_ is the
operator. Led by instinct, or, as the ingenious Sprengel supposes, by
one of those honey marks (_Saftmaal_) or spots of a different colour
from the rest of the corolla, which, according to him, are placed in
many flowers expressly to guide insects to the nectaries, she pushes
herself between the stiff style-flag and elastic petal, which last,
while she is in the interior, presses her close to the anther, and
thus causes her to brush off the pollen with her hairy back, which
ultimately, though not at once, conveys it to the stigma. Having
exhausted the nectar she retreats backwards; and in doing this, is
indeed pressed by the petal to the _arcus eminens_; but it is only to
its lower or negative surface, which cannot influence impregnation. She
now takes her way to the second petal, and insinuating herself under
its style-flag, her back comes into close contact with the true stigma,
which is thus impregnated with the pollen of the first visited anther:
and in this manner migrating from one part of the corolla to another,
and from flower to flower, she fructifies one with pollen gathered
in her search after honey in another.--Mr. Sprengel found, that not
only are insects indispensable in fructifying the different species of
Iris, but that some of them, as _I. Xiphium_, require the agency of
the larger humble-bees, which alone are strong enough to force their
way beneath the style-flag: and hence, as these insects are not so
common as many others, this Iris is often barren, or bears imperfect
seeds[535].
_Aristolochia Clematitis_, according to Professor Willdenow, is so
formed, that the anthers of themselves cannot impregnate the stigma;
but this important affair is devolved upon a particular species of
gnat (_Cecidomyia pennicornis_). The throat of the flower is lined
with dense hair, pointing downward so as to form a kind of funnel
or entrance like that of some kinds of mouse-traps, through which
the insects may easily enter but not return: several creep in, and,
uneasy at their confinement, are constantly moving to and fro, and so
deposit the pollen upon the stigma: but when the work entrusted to
them is completed, and impregnation has taken place, the hair which
prevented their escape shrinks, and adheres closely to the sides of
the flower, and these little go-betweens of Flora at length leave
their prison[536]. Sir James Smith supposes that it is for want of
some insect of this kind that _Aristolochia Sipho_ never forms fruit
in this country.
Equally important is the agency of insects in fructifying the plants
of the Linnean classes _Monoecia_, _Dioecia_ and _Polygamia_, in
which the stamens are in one blossom and the pistil in another. In
exploring these for honey and pollen, which last is the food of
several insects besides bees[537], it becomes involved in the hair,
with which in many cases their bodies seem provided for this express
purpose, and is conveyed to the germen requiring its fertilizing
influence. Sprengel supposes that with this view some plants have
particular insects appropriated to them, as to the dioecious nettle
_Catheretes Urticæ_, to the toad-flax _Catheretes gravidus_, both
minute beetles, &c. Whether the operations of _Cynips Psenes_ be
of that advantage in fertilizing the fig, which the cultivators of
that fruit in the East have long supposed, is doubted by Hasselquist
and Olivier[538], both competent observers, who have been on the
spot. Our own gardeners, however, will admit their obligations to
bees in _setting_ their cucumbers and melons, to which they find the
necessity of themselves conveying pollen from a male flower, when
the early season of the year precludes the assistance of insects.
Sprengel asserts, that apparently with a view to prevent hybrid
mixtures, insects which derive their honey or pollen from different
plants indiscriminately, will during a whole day confine their visits
to that species on which they first fixed in the morning, provided
there be a sufficient supply of it[539]; and the same observation was
long since made with respect to bees by our countryman Dobbs[540].
Thus we see that the flowers which we vainly think are
"... born to blush unseen,
And waste their fragrance on the desert air,"
though unvisited by the lord of the creation, who boasts that they
were made for him, have nevertheless myriads of insect visitants and
admirers, which, though they pilfer their sweets, contribute to their
fertility.
I am, &c.
FOOTNOTES:
[457] Sparrman's _Voyage_, i. 367.
[458] The _Coprion_, _Cantharus_, and _Heliocantharus_ of the
ancients was evidently this beetle, or one nearly related to it,
which is described as rolling backwards large masses of dung, and
attracted such general attention as to give rise to the proverb
_Cantharus pilulam_. It should seem from the name, derived from
a word signifying an ass, that the Grecian beetle made its pills
of asses' dung; and this is confirmed by a passage in one of the
plays of Aristophanes, the _Irene_, where a beetle of this kind
is introduced, on which one of the characters rides to heaven to
petition Jupiter for peace. The play begins with one domestic
desiring another to feed the Cantharus with some bread, who
afterwards orders his companion to give him another kind of bread
made of _asses'_ dung.
[459] PLATE XXII. FIG. 4, 5.
[460] See Latr. _Gen._ i. 275.
[461] This property in the carrion insects may be turned to a good
account by the comparative anatomist, who has only to flay the body
of one of the smaller animals, anoint it with honey, and bury it in
an ant-hill; and in a short time he will obtain a perfect skeleton,
denudated of every fibril of muscle, though with the ligaments and
cartilages untouched.
[462] Gleditsch, _Abhandlungen_, iii. 200.
[463] It is to be observed that in our cold climates, during the
winter months, when excrement and putrescent animal matter are not so
offensive, they are left to the action of the elements, insects being
then torpid.
[464] Curtis _Brit. Ent. t._ 5.
[465] Surely Mr. Marsham's name for this genus, _Boletaria_, is much
more proper than that of Fabricius, _Mycetophagus_ (Agaric-eater),
since these insects seldom eat agarics.
[466] _Œcon. Nat. Amœn. Ac._ ii. 50. Stillingfleet's _Tracts_, 122.
[467] Maupertuis observes, that in Lapland he saw many birch-trees
lying on the ground, which had probably been there for a very long
time, with the bark entire, though the wood was decayed. Hence we may
probably infer, that in that country there are few or none of the
bark-boring insects.
[468] Latreille, _Observations nouvelles sur les Hyménoptères_.
_Annal. de Mus._ 11.
[469] _Nat. Hist. of Carolina_, ii. 105.
[470] Reaum. vi. 282. St. Pierre's _Voyage_, 72.
[471] Bartram in _Philos. Trans._ xlvi. 126.
[472] The larvæ of some species of Coccinellæ feed, according to
Prof. D. Reich, solely on the leaves of plants; as that of _C.
hieroglyphica_, which eats the leaves of common heath (_Erica
vulgaris_) after the manner of the larvæ of _Lepidoptera_. I
suspect, however, that there is some mistake in this statement. _Der
Gesellschaft naturf. Fr. in Berlin Mag._ &c. iii. 294.
[473] Latreille denominates this family, as he calls it, _Pupivora_:
if by this he alludes to their devouring the young of insects, from
the _classical_ meaning of the word _pupa_, the term is very proper;
but this should be borne in mind, as the majority of readers would
imagine it to refer to the _pupa state_ of _insects_, in which they
are not so generally devoured by their parasites.
[474] Not having had it in my power to consult Dalman's work on the
_Chalcidites_ of Latreille, referred to by that learned Entomologist
in his _Familles Naturelles du Règne Animal_, I am not able to refer
them to their proper genera.
[475] PLATE XVI. FIG. 1.
[476] Marsham in _Linn. Trans._ iii. 26.
[477] See above, p. 169-170.
[478] _Alysia Manducator_; and another species allied to _Alomyia
Debellator_, which I have named _A. Stercorator_.
[479] De Geer, ii. 863.
[480] Ibid. 851-5.
[481] Reaum. ii. 419.
[482] De Geer, i. 196. vi. 14. 24.
[483] Reaum. ii. 440-4.
[484] _Linn. Trans._ xi. 86.
[485] Kirby's _Mon. Ap. Ang._ ii. 110-113.
[486] Rossi _Fn. Etrusc. Mant._
[487] Preys. _Bömisch. Insekt._ 59. 61.
[488] PLATE XVII. FIG. 13.
[489] _Entom. Helvétique_, ii. 158.
[490] In the former edition of this work (Vol. IV. p. 392), this
tribe is denominated _Eupodina_; but as this seems too near to M.
Latreille's _Eupoda_, belonging to a different tribe of beetles, we
have substituted the above name, which means the same.
[491] One was taken at Aldeburgh in Suffolk by Dr. Crabbe, the
celebrated poet; another by a young lady at Southwold, which is now in
the cabinet of W. J. Hooker, esq.; and a third by a boy at Norwich,
crawling up a wall, which was purchased of him by S. Wilkin, esq.
[492] Latr. _Hist. Nat._ x. 181.
[493] _Linn. Trans._ vi. 149. Kirby, _Ibid._ ix. 42. 23.
[494] The late R. Kittoe, Esq.
[495] p. 123.
[496] _Voyages_, i. 185.
[497] Percival's _Ceylon_, 307.
[498] Mr. Knight made the same observation in 1806, and supposes the
scarcity of neuters arose from the want of males to impregnate the
females. _Philos. Trans._ 1807, p. 243.
[499] St. Pierre, _Voy._ 72.
[500] Lesser, _L._ i. 263, note.
[501] Reaum. vi. 400. _t._ 36-38. PLATE XVI. FIG. 5. _a._
[502] Thiebaut de Berneaud's _Voyage to Elba_, p. 31.
[503]
"Even Tiger fell and sullen Bear
Their likeness and their lineage spare.
Man only mars kind nature's plan,
And turns the fierce pursuit on Man!"
Scott's _Rokeby_, canto iii. 1.
[504] Reaumur, ii. 413.
[505] De Geer, i. 533. iii. 361. v. 400. vi. 91.
[506] Rösel, iv. 96.
[507] Thunberg's _Travels_, ii. 66.
[508] De Geer, vii. 335.
[509] De Geer, vii. 180.
[510] Bingley, ii. 374.
[511] Bingley, iii. 27.
[512] Collinson in _Philos. Trans._ 1763.
[513] Sparrman, ii. 180.
[514] St. Pierre, _Voy._ 73.
[515] Reaum. vi. 479-487.
[516] Swamm. _Bib. Nat._ i. c. 4. 106. b.
[517] In Col. Venable's _Experienced Angler_, a vast number of
insects are enumerated as good baits for fish, under the names of
_Bob_, _Cadbait_, _Cankers_, _Caterpillars_, _Palmers_, _Gentles_,
_Bark-worms_, _Oak-worms_, _Colewort-worms_, _Flag-worms_,
_Green-flies_, _Ant-flies_, _Butterflies_, _Wasps_, _Hornets_,
_Bees_, _Humble-bees_, _Grasshoppers_, _Dors_, _Beetles_, _a great
brown fly_ that lives upon the oak like a _Scarabee_--(_Melolontha
vulgaris_ or _Amphimalla solstitialis_?) and _flies_ (_i. e._
may-flies) of various sorts.
[518] Anderson's _Recreations in Agricult. &c._, iv. 478. Latr.
_Hist. Nat._ xiv. 154.
[519] According to Mr. Heckewelder (_Trans. Am. Phil. Soc._ iv. 124.)
_L. Excubitor_, called in America the nine-killer, from an idea
that it transfixes nine individuals daily, treats in this manner
_Grasshoppers_ only; while _L. Collurio_ would seem to restrict
itself chiefly to _Geotrupes_, two of which Mr. Sheppard once
observed transfixed in a hedge that he knew to be the residence of
this bird. Kugellan even thinks that it impales only _G. vernalis_,
which he has often found transfixed, but never _G. stercorarius_.
(Schneid. _Mag._ 259.) I must remark, however, that I last summer
observed two _humble-bees_ quite alive, impaled on the thorns of a
hedge near my house, which had most probably been so placed by this
species, _L. Excubitor_ being rarely found except in mountainous
wilds. (Bewick's _Birds_, i. 61.) And Prof. Sander states that on
opening this bird (_L. Collurio_) he has sometimes found in its
stomach nothing but grasshoppers, and at others small beetles and
other insects. _Naturforscher_ Stk. xviii. 234.
[520] Stillingfl. _Tracts_, 175. _Linn. Trans._ v. 105. note^b.
[521] Bingley, ii. 287-290.
[522] Sparrman, ii. 186.
[523] See above p. 208. note^b. and Bewick's _Birds._ i. Pref. xxii.
130.
[524] _Bib. Nat._ i. 126. b.
[525] _Travels_, i. 110.
[526] Reaum. ii. 408.
[527] Bingley, ii. 374.
[528] White's _Selborne_, i. 181.
[529] _Philos. Mag._ xxxix. 107.
[530] Small flies are sometimes found sticking to the glutinous
stigma of some of the Orchideæ like birds on a limed twig: (Sprengel
_Entdecktes Geheimniss_, 21--) and ants are not unfrequently detained
in the milky juice which the touch of even their light feet causes to
exude from the calyxes of the common garden lettuce. _Ann. of Bot._
ii. 590.
[531] _Elements of the Science of Botany_, 62.
[532] Smith's _Introduction to Botany_, 195.
[533] Mouffet, 319.
[534] Smith's _Tracts_, 165. Kölreuter, _Ann. of Bot._ ii. 9.
[535] Chr. Conr. Sprengel _Entdecktes Geheimniss, &c._ Berlin 1793,
4to. quoted in _Ann. of Bot._ i. 414.
[536] _Grundriss der Kräuterkunde_, 353. A writer however in the
_Annual Medical Review_ (ii. 400.) doubts the accuracy of this fact,
on the ground that he could never find _C. pennicornis_, though _A.
Clematitis_ has produced fruit two years at Brompton. Meigen (Dipt.
i. 100. e.) places this amongst his doubtful _Cecidomyiæ_. Fabricius
considers it as a _Chironomus_.
[537] I have frequently observed _Dermestes flavescens_, Ent. Brit.
(_Byturus_) eat both the petals and stamens of _Stellaria Holosteum_;
and _Mordellæ_ will open the anthers with the securiform joints of
their palpi to get at the pollen.
[538] Hasselquist's _Travels_, 253. Latr. _Hist. Nat._ xiii. 204.
[539] Willd. _Grundriss_, 352.
[540] _Phil. Trans._ xlvi. 536.
LETTER X.
_BENEFITS DERIVED FROM INSECTS._
DIRECT BENEFITS.
My last letter was devoted to the indirect advantages which we derive
from insects; in the present I shall enumerate those of a more
_direct_ nature for which we are indebted to them, beginning with
their use as the _food_ of man, in which respect they are of more
importance than you may have conceived.
* * * * *
One class of animals which, till very lately, have been regarded
as belonging to the entomological world, I mean the _Crustacea_,
consisting principally of the genus _Cancer_ of Linné, are universally
reckoned amongst our greatest dainties; and they who would turn with
disgust from a locust or the grub of a beetle, feel no symptoms of
nausea when a lobster, crab, or shrimp is set before them. The fact is,
that habit has reconciled us to the eating of these last, which, viewed
in themselves with their threatening claws and many feet, are really
more disgusting than the former. Had the habit been reversed, we should
have viewed the former with appetite and the latter with abhorrence,
as do the Arabs, "who are as much astonished at our eating crabs,
lobsters, and oysters, as we are at their eating locusts[541]." That
this would have been the case is clear, at least as far as regards the
former position, from the practice in other parts of the world, both
in ancient and modern times, to which, begging you to lay aside your
English prejudices, I shall now call your attention; first observing
by the way, that the insects used as food, generally speaking, live on
vegetable substances, and are consequently much more select and cleanly
in their diet than the swine or the duck, which form a favourite part
of ours.
Many larvæ[542] that belong to the order _Coleoptera_ are eaten
in different parts of the world. The grub of the palm-weevil
(_Cordylia_[543] _Palmarum_), which is the size of the thumb, has been
long in request in both the Indies. Ælian speaks of an Indian king,
who, for a dessert, instead of fruit set before his Grecian guests a
roasted worm taken from a plant, probably the larva of this insect,
which he says the Indians esteem very delicious--a character that was
confirmed by some of the Greeks who tasted it[544]. Madam Merian has
figured one of these larvæ, and says that the natives of Surinam roast
and eat them as something very exquisite[545]. A friend of mine, who
has resided a good deal in the West Indies, where the palm-grub is
called _Grugru_, informs me that the late Sir John La Forey, who was
somewhat of an epicure, was extremely fond of it when properly cooked.
The larvæ also of the larger species of the capricorn tribe
(_Cerambyx_, L. _Longicornes_, Latr.) are accounted very great
delicacies in many countries; and the Cossus of Pliny, which he
tells us the Roman epicures fattened with flour[546], most probably
belonged to this tribe. Linné indeed, following the opinion of
Ray[547], supposes the caterpillar of the great goat-moth, the
anatomy of which has been so wonderfully traced by the eye and
pencil of the incomparable Lyonet, to be the Cossus. But there seems
a strong reason against this opinion; for Linné's Cossus lives
most commonly in the willow, Pliny's in the oak; and the former
is a very disagreeable, ugly and fetid larva, not very likely to
attract the Roman epicures. Probably they were the larvæ of _Prionus
coriarius_, which I have myself extracted from the oak, or of one
of its congeners[548]. The grub of _P. damicornis_, which is of
the thickness of a man's finger, is eaten at Surinam, in America,
and in the West Indies, both by whites and blacks, who empty, wash,
and roast them, and find them delicious[549]. Mr. Hall informs me,
that in Jamaica this grub is called _Macauco_, and is in request
at the principal tables. A similar insect is dressed at Mauritius
under the name of _Moutac_, which the whites as well as Negroes eat
greedily[550]. The larva of _P. cervicornis_ is, according to Linné,
held in equal estimation, and that of _Acanthocinus Tribulus_ when
roasted forms an article of food in Africa[551]. It is probable that
all the species of this genus might be safely eaten, as well as many
other grubs of _Coleoptera_; and although I do not feel disposed to
recommend with Reaumur[552], that the larvæ of _Oryctes nasicornis_
should be sought for "_dans les couches de fumier_," yet I think with
Dr. Darwin[553], that those of the cockchafer which feed upon the
roots of grass, or the perfect insects themselves, which, if we may
judge from the eagerness with which cats, and turkeys and other birds
devour them, are no despicable _bonne bouche_, might be added to our
_entremets_. This would be one means of keeping down the numbers of
these occasionally destructive animals.