MYRMELEON AMERICANUM. Thorace griseo nigro notato, alis hyalinis fusco et
luteo punctatis, punctis nonnullis lineam centralem longitudinalem
formantibus, abdomine fusco. (Expans. Alar. 5 unc.)
SYN. Myrmeleon americanus, _Drury, App. vol._ 2.
HABITAT: New York.
Head black, front grey and hairy. Mouth with four long palpi. Eyes dark
brown, almost black. Antennæ black, and as long as the thorax; being
small at the base, and increasing in size to their extremities. Neck
yellowish, striped with black, and covered with longish grey hairs.
Thorax yellowish, with black stripes, and covered with long grey hairs.
Abdomen, which is full an inch and a half long, brownish-coloured, and
darker on the sides; being furnished at the extremity with two short
hairy tails, seemingly of a horny substance. Wings of equal length,
membranaceous and transparent, having a great number of small spots
thereon of a dark brown colour; the superior ones being most spotted.
Legs black, and covered with grey hairs; each of them being furnished at
the tips of the tibiæ with two long spines that bend inwardly towards
each other.
----
LIBELLULIDÆ, Pl. 47 & 48.
All the insects represented in these two plates belong to the genus
Libellula of Linnæus, or the family of Dragon-flies, Libellulidæ. When the
original edition of this work was published, there was no English work in
which the natural history and curious transformations of this tribe of
insects were detailed. Our author, therefore, in order to supply the
deficiency, published the following interesting series of observations upon
the subject:--
"As I have not met with any English author who has given the natural
history of the insects delineated in these two plates, I shall make no
apology for its introduction; {107}the frequent opportunities I have had of
observing their mode of life and action, together with the many singular
circumstances observable in both, being motives for its publication too
powerful to be resisted.
"It is not easy to determine whether they should be ranked among the water
insects, or those of the land, nor shall I attempt here to ascertain it; my
present business being only to relate the several circumstances attending
them during their respective states in which they are passing from the egg
to the complete animal: and although these observations have been confined
to our English ones, yet they so exactly agree and coincide with those of
foreign countries, (as my correspondents have assured me), that their
nature and behaviour appear to be just the same; so that what is observable
in ours, is at the same time applicable to the whole genus wherever found.
"If we take a cursory view of the different ranks of animals that inhabit
our globe, we shall hardly find one that can excite our wonder and
astonishment more than this genus; nor is it from that general ignorance of
the insect world, that reigns so strongly in these kingdoms, that I am
emboldened to say this; but if we reflect that the beasts, birds, and
reptiles are furnished with powers for living only in the air, and that
even the amphibious tribes can perform the office of respiration only in
that element: if we also consider that fishes, on the contrary, are unable
to respire but in water, and when deprived of that must certainly perish,
we cannot but conclude that all these animals are most wisely fitted with
means and faculties for filling up the respective orders and ranks wherein
they are placed. But let us cast our eyes on the subjects I am about to
describe, and there behold a tribe of beings, who, as soon as they leave
their eggs, subsist for a certain number of months, (I had almost said
years), creeping and swimming in the liquid element; are there invested
with organs and powers for existing and weathering out the utmost severity
and intemperance of the winter; that afterwards as the spring and summer
advances, and the period arrives when they are to appear in other forms, in
the space of about half an hour those very organs and powers that before
enabled them to live under water should be so entirely altered, the very
natures and abilities of the creatures so changed as to permit them to quit
their former element and place of residence, insomuch that all the
remaining part of their lives is spent in the open air, furnished with
wings, and flying about in the full glee of wanton liberty; that in a very
few weeks after, having performed the business of generation, the same
animals should die of mere old age, with their wings quite ragged and worn
out, their strength exhausted, and all the powers of their bodies lost by a
total imbecility and weakness, which but a little before enabled them to
transport themselves through the air with the swiftness of a bird. If, I
say, we reflect on all these circumstances, we cannot but allow them to be
objects of a very extraordinary nature, and well adapted for leading the
mind to the contemplation of their supreme Author, who has thought proper
to exhibit to us these kind of insects, thus differing from almost all the
animals in the creation.
{108}"They have been variously named by different authors, owing perhaps to
the time when they wrote, or the progress natural history had made in the
world. Some have called them by the name of Dragon Fly, others Adder Bolt,
Balance Fly, Perla, Libellula or Libella. I shall prefer the last, as
conveying an idea well known to English adepts. The caterpillars of them
all live in ponds and stagnant waters (that are undisturbed by cattle)
during the greatest part of their lives, and make their appearance under
three general forms. The first is shewn by Fig. 1. 1.; the second by Fig.
2.; and the third by Fig. 3. See Plate 47. As these are the shapes in which
they all appear, it will not be improper to mention each particularly.
"The two caterpillars at Fig. 1. 1. Plate 47, belong only to or produce
those that sit at rest, with their wings erect, (see Plate 48. Fig. 2.),
and differ from both the others not only in size but in the roundness and
slenderness of their bodies; at the extremity whereof they are furnished
with three tails, each of which upon examination being found to be a kind
of feather, and is an appendage that neither of the others have. Their
behaviour also in the water is different from the others, being enabled to
twist and bend their bodies in a more circular manner. [Subfamily
Agrionides.]
"The second sort of caterpillars, at Plate 47. Fig. 2. are much shorter and
thicker in their bodies than either of the others, producing those Libellas
with flat bodies, as Plate 47. Fig. 4. and 6. and Plate 48. Fig. 1. and 5.
These are, of all others, the most disagreeable in their appearance; most
of them having their bodies and legs very rough and shaggy, and of the
exact colour of mud. Others appear of a dirty green, and very unpleasing
hue, a colour that in general reigns among them all; for none can boast of
any beautiful appearance while in this state, unless the different shapes
here exhibited can be called so. Indeed the beauty and symmetry, so
apparent in their complete states, make ample amends for the want of it in
this; all of them in general being then very beautiful, discovering colours
superior to art. [Subfamily, Libellulides. Genus, Libellula.]
"The caterpillars of the third sort (see Plate 47. Fig. 3.) are very
different from the preceding, being the size of the figure, with the
abdomen flat at bottom and rounding at top, longer and slenderer than those
at Fig. 2. but not so much as those at Fig. 1. 1. These produce those large
Libellas with long slender bodies, who sit at rest with their wings
expanded, as Plate 47. Fig. 5. [Subfamily, Libellulides. Genus, Æshna.]
"Under these three forms are all the caterpillars of Libellas found, there
being but little difference in the colours or marks of the respective
tribes; the various sizes and shapes being the chief observable
circumstances attending them. They are all furnished with six legs, and
have each of them four little membranaceous substances issuing from the
back, or upper part of the thorax, that are the follicles, or cases,
wherein the wings are inclosed. When the young caterpillars issue from
their confinement in the eggs, there is no appearance of these cases, nor
till a considerable time after; but as they arrive to a maturer state they
become more conspicuous, and, like the young leaves of trees that open
{109}and expand themselves on the arrival of the spring, their appearance
increases, till having approached the period when they are to forsake their
former habitations and become inhabitants of the air, these wing-cases have
then arrived to their due size, and carry the appearance in which they are
here seen. They are all of them, from the largest to the smallest, armed
with a strong offensive weapon, which serves them, and is indeed the means
they are endued with, for obtaining their food. This weapon being placed in
the under part of the head, just beneath the mouth, I have displayed in
Fig. 1. and 3. of Plate 47. where it appears just in the same manner as
when they are endeavouring to catch their prey. In the largest figure at 1.
and also in Fig. 2. it appears contracted and shut up, as when at rest. The
strength and power that these animals discover in the use of this
instrument is very singular and extraordinary. There are two joints to it,
one about the middle, the other underneath the mouth, close to the throat;
and in some (particularly all those of Fig. 2.) when it is closed or
contracted, it appears fastened to the face of the creature, by fitting it
so exactly as to form a perfect mask; covering the mouth, and reaching
almost as high as the eyes. In others it is made to fit only the under part
of the mouth, and when at rest is drawn up close underneath it. At the
extremity of those that are extended may be observed two very strong and
remarkable fangs; that, shutting over each other, form a pair of forceps,
of such strength that few, if any of their captives, can escape if once
inclosed therein. [This organ is the greatly developed lower lip of the
larva, and is analogous in its structure to the same part in the imago.]
"The motion of these creatures in the water, particularly those of the
largest size, is very slow; seldom exercising any swiftness or activity,
unless they are disturbed and threatened with danger, in which case they
can transport themselves to places of more security with the quickness or
agility of a fish; but, in general, they appear to have so little
inclination to move, that I have often seen them (I mean those that I have
kept in glass bowls) remaining in their respective places above a week
together, and could not discover the least motion in them, unless under the
circumstance above mentioned, or when they had seen their prey and were
advancing to seize it. The caterpillars of Fig. 1. 1. and 3. generally fix
themselves to some little stick or straw, &c. that they find in the water,
and there remain, as I said before, without stirring. Those of Fig. 2. are
more frequently seen in motion among the thickest part of the roots and
plants that grow there, routing and searching for those small animals
inhabiting that part, which are their proper food. This aversion to motion,
so apparent in those of No. 1. and 3., appears to me to be the effect of an
extraordinary cunning and sagacity; and may be considered as the principal
means by which they obtain their prey: for while they continue thus
motionless in the water, the small animals, who constitute their proper
food, approach them with less fear than they would otherwise do, not
suspecting their grand enemy lies upon the watch to seize them the moment
they come within his reach; but no sooner has their insensibility of danger
brought them within a small distance of those destructive weapons
(mentioned before, being placed under their mouths) but that very instant
they dart upon them with {110}the utmost rapidity, suddenly throwing out
their forceps, and seizing them with as much eagerness as a pike does the
unwary gudgeon; they then bring their forceps up to their mouth with their
prey in it, and feast on their captive prisoner. Nor is their voracious
nature less astonishing; and the greediness with which the large ones seize
other small animals would hardly gain belief among persons entirely
ignorant of this study. I have seen one of them, in less than an hour's
space, devour three insects, each of which was full two thirds as big as
itself; but, in general, the small ones are the sacrifices made by the
greater; wherein I must observe, that when they have got a caterpillar of
the small Libellas in their forceps, such as those of Fig. 1. Plate 47.,
they leave no part uneaten, except the three tails, which they let fall to
the bottom, as perhaps not having substance in them sufficient to afford
them proper nourishment; for as their food consists altogether of animals
less than themselves, they neither spare the caterpillars of the lesser
Libellæ, nor confine themselves to those belonging to other tribes. They
will eagerly prey upon the different kinds of Cads, or caterpillars of the
Phryganeæ; great numbers of whom, at certain seasons, quit those husks or
cases they make and swim about, with less fear and dread than in the early
part of the spring. I have also seen the caterpillars of the Notanecta's or
Boat-flies devoured by them, and not seldom the small blood-worms, as they
are called. In short, there are but few of the lesser animals that live in
the water, but when once they get within the reach of their instruments
will certainly fall victims to these freshwater Leviathans.
"I could never observe that these caterpillars ever threw off any exuvia,
or skin, in their progress from the egg to the complete animal, as most
other insects do that live in the open air; neither could I ever perceive
any difference between the caterpillars and chrysalis's of this genus in
their outward forms[31]: the same voracious behaviour in seizing and
devouring their prey, reigning both in one and the other; but that they
internally undergo some material alteration, when passing their respective
states, is what I do not entertain the least doubt of; as the organs of
respiration during the creature's life in the water, appear to me to be
under a necessity of receiving a great alteration, when they are to perform
the same office in so different a medium as the air; nor can I suppose this
business to be done in so quick and sudden a manner, as the short space of
time in which the creature would then be passing from the caterpillar state
to the perfect one would permit, without having the intestines prepared, as
it were, and fitted by some previous change. However, as this is conjecture
only, I shall dwell no longer on this head, my present purpose being to
point out and describe their general circumstances and behaviour.
"When the caterpillars of the respective species have arrived to their full
growth, and nature informs them they are to quit their former element of
water, for one wherein they are to appear invested with very different
powers, they prepare for this extraordinary change; and, creeping up the
sticks, straws, or plants they find for their purpose, whose tops grow out
of the water, they entirely quit that element, and, stopping at about six
or {111}eight inches above its surface, there fix themselves, and continue
some time, till their internal form, growing too big to be confined within
the skin, that a few minutes afterwards will be entirely thrown off, on a
sudden, that part of it that covers the thorax, splits or bursts on the
upper side, and the creature, pushing out its head, next disengages its
fore legs, which fastening to any substance within its reach, draws gently
the remainder of its body and legs entirely out, just as a man draws his
leg out of a boot, leaving its slough or skin sticking in its place, and in
the exact form wherein it appeared itself but a few moments before. Having
thus quitted its former covering, it waits for the wings to expand
themselves, and grow to their proper size, being before confined within
those small cases I mentioned were placed on its back. In about half an
hour, if the weather is favourable, this extraordinary operation is
completed; and the wings having arrived to their proper size, the creature
generally makes an effort to try its strength, well knowing, that if it
fails in attempting to fly without being endued with a sufficient degree of
it, it must certainly fall in that water it lately quitted, and there
perish; but having made several motions with its wings, and finding its
power equal to its desire, it suddenly flies into the air, and there fills
up a character, as different from the former as one element is from the
other. At the time this change is accomplishing, the instrument or weapon
for catching their prey, before mentioned, by an effect of nature, totally
disappears, and not the least vestige of it then remains; the mouth,
indeed, is furnished with jaws, and those of a very extraordinary form
(dividing themselves both horizontally and perpendicularly), but no part of
them appear extended beyond the rest, or have the least appearance of being
furnished with an instrument like what they had in their former state.[32]
"Hitherto I have considered these creatures only in their infant or
incomplete states; wherein the faculties and powers they are endued with,
are entirely different from those of their perfect and complete ones. In
the former I have described them swimming and grovelling about in the
water, preying upon the lesser kinds of insects, being incapable of
subsisting for any length of time out of that element; in the latter we
must view them capable of flying in the open air, and conveying themselves
from place to place. If they are then confined to the limits of a small
pond, they are now capable of roving from tree to tree, and from field to
field, darting and skimming along with all the rapidity and seeming joy,
that a being sensible of, and exulting in its own powers, can be supposed
to do; in short, we {112}must now view them in shapes so distinct and
different from their former ones, that they hardly seem to bear any
relation to each other, except in their nature and appetites; for although
they appear in a far more elegant dress than when in their caterpillar
states, yet these are just the same, the same voracious inclinations
subsisting now as formerly; hunting after, and preying upon, the lesser
genera, with the same eagerness and desire as they did when inhabitants of
the water. Incredible numbers of small moths, bees, flies with four and two
wings, are the daily sacrifices offered to the insatiable appetites of
these hungry gluttons; and where they devoured one insect in the water they
now destroy a hundred, if the mildness of the season will permit them to
range about in quest of them. In rainy weather they seldom or ever move,
nor when the wind is very strong and boisterous. Indeed, it is not to be
wondered at. The small insects, who are their proper food, being by the
same reasons prevented from being abroad, consequently are an impediment to
those motives, that so strongly induce the Libellas to fly about. During
such inclement times they generally shelter themselves from the wind, &c.
being suspended by their feet in a perpendicular position on some twig,
that is remote and separate from any boughs, waiting in that manner,
without motion, for better weather and sunshine.
"I am strongly inclined to believe, that the greater part, if not all the
Libellas, are two years in passing from the egg to the complete animal. But
as this is a circumstance I do not remember to have seen in any author, I
shall not attempt to establish my opinion as an absolute truth. I shall
mention my reasons for this belief, and leave it to every person either to
confirm or confute it, as his observations shall hereafter give him an
opportunity.
"In order to do this, it would be necessary I should mention the times when
each species first makes its appearance here in England. But as this would
not only take up too much of the reader's time, (there being at least
twenty-two of them) but it would likewise be impossible to be understood by
any, but the experienced adept, unless I gave figures of them all; I shall
therefore content myself with observing, that the Libella figured in Plate
47. Fig. 5. though found in America, about New York, &c. is nearly the same
with our English one, differing but a very little from it, and which I have
inserted chiefly as an instance to illustrate this subject. Ours is the
last species but one, that comes forth in the summer, breeding only once a
year, appearing about the 2nd of August. Therefore, to elucidate this
point, suppose we allow a fortnight or three weeks from that time for all
the Libellas of this species to make their appearance in, that nature
intended should be bred that year; but in order to set this matter in the
strongest light, I shall allow a month to that purpose. If, therefore, the
Libellas were only one year in passing from the egg to the perfect state,
we might justly conclude, that after the 2nd of September, (a month from
the time of their first appearing) all of this species would have arrived
to their complete states; and that none of their caterpillars could be
found in the waters after that time, by reason they had all quitted that
element, and were become flying insects. This, I say, is the conclusion we
might fairly, and without presuming on the matter, make. But this is
{113}very far from being the case. For let any one examine stagnant waters
at any time during the months of August, September, or October, and from
thence in any part of the following winter, and he will find these very
caterpillars at any of those times: and this, not in any one particular
year, but they will be found also in any one whatever, fully fed, and of
the largest size. Nor are the caterpillars of this species the only ones to
be found fully fed. Those of No. 2. belonging to the flat-bodied Libella,
will also be found very plentifully, many of them being of the first
magnitude, together with numbers of the same species, very young according
to the time of year when sought for; and appearing to have been hatched
from those eggs that were laid by parent insects in the spring; for such I
must conclude them to be, how else can we account for their smallness, at
the same time that we may find others of the largest size? We must not
suppose there can be this difference of size in the same species, owing to
some eggs having been laid three weeks or a month sooner than others; that,
being so short a space of time as not to allow it possible for one of those
caterpillars to attain its full size, (and all the species of flat-bodied
Libellas appear within a month of each other.) Nor can we be so deceived as
to mistake a species of the long-bodied caterpillars, for one of the
short-bodied; the difference being extremely apparent at the first glance.
"These reasons appear to me so convincing, I should have thought myself
inexcuseable to have passed them over in silence, when I was giving the
history of these animals. I shall therefore think myself happy to have this
circumstance corroborated by future experience, or rectified and cleared
up, if found to be an error. I shall only say, I have dwelt the longer on
it, as it is an observation I never heard of before. I have likewise
singled out the largest Libella, and the flat-bodied ones for its
illustration, as being more conspicuous by their size, and easier to be
observed than those of the smaller sorts.
"The two principles of hunger and lust, so apparent through the animal
kingdom, are in no class or tribe more manifest and visible than in these
insects. The former I have described and explained through their different
states; it remains for me to shew the manner in which they obey the calls
of the latter. And herein I must observe, that the different manner in
which the act of copulation is performed, depends on the difference of the
respective kinds; the organs of generation being placed in different parts
of the body, according to the distinct species. All the flat-bodied ones
have those parts placed in common with most other insects, at the extremity
of the tail. In all the slender-bodied ones, the organ of the male is
placed next the breast, close to the part where the thorax and abdomen
unite; while the same organ in the female lies in the very extremity of the
tail, and the singular manner of these creatures coupling is a circumstance
worthy of observation.
"As soon as they have arrived to their perfect state, the males seek out
their mates, in order to propagate their species; for this purpose they
frequent ponds and standing waters, places where the females generally
harbour, and when the male in the course of his flight comes within a
certain distance of her, if it be one of that species whose sexual parts
{114}in both sexes are placed in the tail, he immediately flies to her, and
fixing himself by his feet to the hinder part of her abdomen, bends his
body round her tail, and performs the business of generation, both flying
about all the time this act is performing; the whole transaction not
exceeding the space of half a minute. Within a few hours after, the female,
thus impregnated, begins to lay her eggs in the following manner. She
singles out a leaf, grass, or some such matter, that is floating just below
the surface of the water, in some pond, and, hovering in the air about a
foot above this spot, on a sudden she descends, and dips the extremity of
her tail in the water, at which instant she discharges an egg, that at the
moment of its emission is inveloped in a glutinous liquid, sufficiently
tenacious to enable it to adhere firmly on the floating substance
above-mentioned without sinking. In this manner she continues depositing
them till she has discharged the proper quantity, hovering in the air all
the time, and emitting them as fast as the pendulum of a clock performs its
vibrations; placing them close to one another in no regular or exact order.
Whether she discharges at one time all her quantity of eggs, or only those
that were fecundated and ready for emission, waiting to have the remaining
eggs within her again fecundated by the male, or whether the first act of
copulation sufficiently impregnates the whole quantity which she discharges
at different times, as nature ripens them, is a circumstance I cannot
determine. However this may be, it is certain she does not discharge them
all at once; but comes again to the same place, when those within her are
ready for emission, and there lays them in the same manner as at first.
"In this manner all the flat-bodied Libellas copulate and lay their eggs;
the others, which are formed with slender bodies, behave very differently
in every circumstance; for in each of those species, when the male has
singled out its mate, he flies to her, and by means of two little bony
substances placed at the end of his tail, issuing on each side, and
composing a kind of forceps, he fixes himself to the forepart of her neck,
close behind the head, the female discovering no sign of fear while he is
performing this action; having fixed himself in this position, he remains
there several days, sometimes appearing with his body quite erect, at other
times bending himself, and settling with his legs on the same substance she
may happen to alight on, without ever quitting his hold; but flies through
the air, thus united, wherever the fancy or inclination of the female
disposes her to go. This behaviour we must consider as a prelude to
copulation, for that is not performed till a considerable time after they
are thus united; and therefore I look on it as a wooing, or act of
courtship in the male. But having remained a sufficient time in this
manner, that is, till the female is disposed to receive him, she bends her
tail round to that part where I described the organ of generation to be
placed in the male, and, being still held fast by the neck, in that
attitude they perform the mandate of nature. This action being over, that
in the smaller kinds takes up a considerable space of time (for I have
known them in this posture above eighteen hours) the female soon after
begins to lay her eggs. She flies to some rush, reed, or other plant
growing in the water, and settling close to its edge dips {115}the end of
her tail a little below the surface, and fixes her eggs to the rush or
substance she is settled on; which, by means of the glutinous matter all
eggs of this kind are surrounded with, adheres sufficiently fast, and there
remains till the heat of the sun has brought the young animal into life;
which immediately on quitting its confinement sinks to the bottom, or
repairs to the place where nature directs it to seek out its food.
"In this manner all the slender-bodied tribe behave, differing only in some
particular circumstances; as, for instance, the largest Libellas, as that
at Fig. 5. Pl. 47. are not near so long in copulating or wooing as the
small ones; for by the former this act is performed in a very short space,
and while they are flying about in the air. Others, of a smaller size, are
less quick in this performance; and as we descend to the smallest species,
we shall find they take by much the longest time; observing, by the way,
that all these slender-bodied ones lay their eggs in the same manner, that
is, by fixing them to some substance to which they adhere, till they are
ripened into life. My experience well informing me they never scatter them
in any loose careless manner as some insects do, but are placed in such
proper and apt situations as to receive the influence of the sun to bring
them to maturity.
"If we attentively consider these creatures, either in their caterpillar or
complete states, we cannot help concluding them to be a rank of beings of
greater benefit and advantage to mankind than they appear to be at first
view; for, not to mention their being annual 'ministers of nature,' they
are appointed by the great Governor of the universe as grand instruments
for assisting to preserve that equilibrium so apparently reigning through
the insect world, and which all who have made any progress in the study of
natural history unanimously confess. Hence the voracious disposition of the
Libellas is wisely made to answer a most necessary and beneficial purpose;
and the great numbers of small insects which are daily sacrificed to their
insatiable appetites, both in their caterpillar as well as complete states,
is as strong an instance as any I know of the necessity and propriety of
the existence of these animals. The general principle reigning through the
whole animal kingdom, of the stronger preying upon the weak and
defenceless, can hardly be explained to the purpose of being useful to
mankind, and agreeable to the laws of nature, in any one instance more than
is evidently to be observed in the subjects I have been describing. The
least reflection will confirm this; for if the food of the Libellas when in
their complete forms had consisted of the leaves of plants, like the locust
genus, and not of those small insects they now prey on; or had it, like the
beetle tribe, consisted of the superfluous parts of nature, as the putrid
carcases of dead animals, rotten wood, &c. how great a chasm would there
have been in the universal chain? how evident and conspicuous would it have
appeared? and how could the vast number of small insects, increasing every
day during the summer, be restrained and lessened? what genus of the
transparent-winged class could possibly have performed this business
singly? or could all the genera of flies, and even birds that we know of,
have accomplished this end? could all the Dipteræ, or any other {116}kinds
that prey on the lesser genera, have prevented such an increase of them as
to become in a little time a plague too great to be borne? No. The Almighty
Creator has most wisely constituted this genus for executing His commands
in the manner I have described; and for this reason they must be considered
as beings of greater consequence than the inconsiderate part of mankind
allow them to be.
"Nor is this the only advantage arising from their existence. The still
waters, where these creatures are inhabitants during their infant state,
are in some degree by their assistance preserved sweet and good, that
otherwise might corrupt and putrify, for the motion the waters receive by
these insects is not trifling; the respiration they perform in that element
being observable by a close attention, which, together with that and the
motion of thousands of other insects, does in some measure contribute to
keep it sweet and wholesome."