LETTER XII.

_ON THE FOOD OF INSECTS._

Insects like other animals draw their _food_ from the vegetable and animal kingdoms; but a very slight survey will suffice to show that they enjoy a range over far more extensive territories.

To begin with the vegetable kingdom.--Of this vast field the larger animals are confined to a comparatively small portion. Of the thousands of plants which clothe the face of the earth, when we have separated the grasses and a trifling number of herbs and shrubs, the rest are disgusting to them, if not absolute poisons. But how infinitely more plenteous is the feast to which Flora invites the insect tribes! From the gigantic banyan which covers acres with its shade, to the tiny fungus scarcely visible to the naked eye, the vegetable creation is one vast banquet at which her insect guests sit down. Perhaps not a single plant exists which does not afford a delicious food to some insect, not excluding even those most nauseous and poisonous to other animals--the acrid euphorbias, and the lurid henbane and nightshade. Nor is it a presumptuous supposition that a considerable proportion of these vegetables were created expressly for their entertainment and support. The common nettle is of little use either to mankind or the larger animals, but you will not doubt its importance to the class of insects, when told that at least thirty distinct species feed upon it. But this is not all. The larger herbivorous animals are confined to a foliaceous or farinaceous diet. They can subsist on no other part of a plant than its leaves and seeds, either in a recent or dried state, with the addition sometimes of the tender twigs or bark. Not so the insect race; to different tribes of which every part of a plant supplies appropriate food. Some attack its roots; others select the trunk and branches; a third class feed upon the leaves; a fourth with yet more delicate appetite prefer the flowers; and a fifth the fruit or seeds. Even still further selection takes place. Of those which feed upon the roots, stem, and branches, of vegetables, some larvæ eat only the bark (_Sesia apiformis_, &c.), others the alburnum (_Semasia Wœberana_), others the exuding resinous or other excretions (_Scoparia Resinella_), a third class the pith (_Xanthia Ochraceago_), and a fourth penetrate into the heart of the solid wood (_Prionus_, _Lamia_, _Cerambyx_, &c.). Of those which prefer the leaves, some taste nothing but the sap which fills their veins (_Aphides_ in all their states), others eat only the parenchyma, never touching the cuticle (subcutaneous _Tineæ_, _Gracillaria?_) others only the lower surface of the leaf (many _Tortrices_), while a fourth description devour the whole substance of the leaf (most _Lepidoptera_). And of the flower-feeders, while some eat the very petals (_Cucullia Verbasci_, _Xylina Linariæ_, &c.), others in their perfect state select the pollen which swells the anthers (bees, _Lepturæ_, and _Mordellæ_), and a still larger class of these the honey secreted in the nectaries (most of the _Lepidoptera_, _Hymenoptera_, and _Diptera_).

Nor are insects confined to vegetables in their recent or unmanufactured state. A beam of oak when it has supported the roof of a castle five hundred years, is as much to the taste of some, (_Anobia_,) as the same tree was in its growing state to that of others; another class (_Ptini_) would sooner feast on the herbarium of Brunfelsius, than on the greenest herbs that grow; and a third (_Tineæ_, _Termites_), to whom

"... a river and a sea Are a dish of tea, And a kingdom bread and butter,"

would prefer the geographical treasures of Saxton or Speed, in spite of their ink and alum, to the freshest rind of the flax plant.--The larva of a little fly (_Oscinis cellaris_), whose economy, as I can witness from my own observations, is admirably described by Mentzelius[703], disdains to feed on any thing but wine or beer, which like Boniface in the play it may be said both to eat and drink, though, unlike its toping counterpart, indifferent to the age of its liquor, which whether sweet or sour is equally acceptable.

A diversity of food almost as great may be boasted by the insects which feed on animal substances. Some (flesh-flies, carrion-beetles, &c.) devour dead carcases only, which they will not touch until imbued with the _haut gout_ of putridity. Others, like Mr. Bruce's Abyssinians, preferring their meat before it has passed through the hands of the butcher, select it from living victims, and may with justice pride themselves upon the peculiar freshness of their diet. Of these last, different tribes follow different procedures. The Ichneumons devour the flesh of the insects into which they have insinuated themselves. Some of the Œstri, fixed in a spacious apartment beneath the skin of an ox or deer, regale themselves on a purulent secretion with which they are surrounded. Others of the same tribe, partial to a higher temperature, attach themselves to the interior of the stomach of a horse, and in a bath of chyme of 102 degrees of Fahrenheit revel on its juices. The various species of horse-flies dart their sharp lancets into the veins of quadrupeds, and satiate themselves in living streams; while the gnat, the flea, the bug, and the louse, plunge their proboscis even into those of us lords of the creation, and banquet on "the ruddy drops which warm our hearts." Some make their repast upon birds only, as the fly of the swallow, and other _Ornithomyiæ_, and the bird-louse; insects nearly allied, though one is dipterous and the other apterous. And a most singular animal belonging to the latter tribe (_Nycteribia Vespertilionis_) revenges upon the bat its ravages of the insect world[704]. Another numerous class kill their prey outright, either devouring its solid parts, as the predaceous and rove-beetles, &c., or imbibing its juices only, as the infinite hordes of the field-bug tribe. And the larvæ of the gnat, chameleon (_Stratyomis_), and other flies aquatic in that state, the leviathans of the world of animalcules, swallow whole hosts of these minute inhabitants of pools and ponds at a gulp, causing with their oral apparatus a vortex in the water, down which myriads of victims are incessantly hurried into their destructive maw.

But not only animals themselves, almost every animal substance that can be named is the appropriate food of some insect. Multitudes find a delicious nutriment in excrements of various kinds. Matters apparently so indigestible as hair, wool, and leather, are the sole food of many moths in the larva state (_Tinea tapetzella_, _pellionella_, &c.). Even feathers are not rejected by others; and the grub of a beetle (_Anthrenus Musæorum_), with powers of stomach which the dyspeptic sufferer may envy, will live luxuriously upon horn[705].

For the most part, insects feeding upon animal substances will not touch vegetables, and _vice versâ_. You must not however take the rule without exceptions. Many caterpillars (as those of _Thyatira derasa_, _Chariclea Delphinii_, &c.), though plants are their proper food, will occasionally devour other caterpillars, and sometimes even their own species. The large green grasshopper (_Acrida viridissima_), and probably others of the order, will eat smaller insects as well as its usual vegetable food[706]; so also will the larvæ of many _Phryganeæ_. _Allantus marginellus_, as I was last summer amused by witnessing, like many _Scatophagæ_, sips the nectar of umbelliferous plants only till a fly comes within its reach, pouncing upon which it gladly quits its vegetable for an animal repast. _Anobium paniceum_, which ordinarily feeds upon wood, was, as I before mentioned, once found by Mr. Sheppard in great abundance living upon the dried Cantharides (_Cantharis vesicatoria_) of the shops. On the other hand, _Necrophorus mortuorum_, which subsists on carcases, and many other carnivorous species, will make a hearty meal of a putrid fungus; _Ptinus Fur_ devours indifferently dried birds or plants, not refusing even tobacco; and from the impossibility that one of a million of the innumerable swarms of gnats which abound in swampy places, particularly in regions which but for them would be lost to sensitive existence, should ever taste blood, it seems clear that they are usually contented with vegetable aliment. Indeed the males, as well as those of the horse-fly of which even the females readily imbibed the sugared fluid offered to them by Reaumur[707], never suck blood at all; so that they must either feed on vegetable matter, which in fact I have observed them to do, or fast during their whole existence in the perfect state.

Though insects, generally considered, have thus a much more extensive bill of fare than the larger animals, each individual species is commonly limited to a more restricted diet. Many both of animal and vegetable feeders are absolutely confined to one kind of food, and cannot exist upon any other. The larva of _Gasterophilus Equi_ can subsist no where but in the stomach of the horse or ass, which animals therefore this insect might boast with some show of reason to have been created for its use rather than for ours, being to us useful only, but to it indispensable. The larvæ of _Syrphus Pyrastri_ according to De Geer eat no other Aphis but that of the rose[708]. Most Ichneumons and _Sphecina_ prey each upon a single species of insect only, which therefore they would seem to have been formed for the express purpose of keeping within due limits. Reaumur mentions having once found in a parcel of decaying wood the nests of six different kinds of the latter tribe, each of which was filled with flies of a distinct species[709]. _Cerceris auritus_ and _Philanthus lætus_ in the larva state feed solely on the weevil tribe of _Coleoptera_, the latter being restricted even to the short-rostrum'd family, as _Otiorhynchus raucus_, &c.[710], while _Bembex rostrata_, another hymenopterous insect, selects flies, as _Musca Cæsar_, &c.[711]

A very large proportion of species, however, are able to subsist on several kinds of food. Amongst the carnivorous tribes, it is indifferent to most of those which prey upon putrid substances from what source they have been derived: and the predaceous insects, such as the _Libellulina_, _Telephorus_, _Empis_, the _Araneidæ_, &c. will attack most smaller insects inferior to them in strength, not excepting in many instances their own species. The wax-moth larva (_Galleria Cereana_) will for want of wax eat paper, wafers, wool, &c.[712]: another Tinea described by Reaumur, and before adverted to, attacks chocolate[713], which cannot have been its natural food, even selecting that most highly perfumed; and the Tineæ which devour dressed wool, but happily for the farmer and wool-stapler refuse it when unwashed, must have existed when no manufactured wool was accessible.--The vegetable feeders are under greater restrictions, yet probably the majority can subsist on different kinds of food. This is certainly true of most lepidopterous larvæ, several of which as well as many _Coleoptera_ (_Haltica oleracea_, &c.) are polyphagous, eating almost every plant. It is worthy of remark, however, that when some of these have fed for a time on one plant they will die rather than eat another, which would have been perfectly acceptable to them if accustomed to it from the first[714]. Here too it must be borne in mind, that by far the greater part of insects feed upon different substances in their different states of existence, eating one kind of food in the larva and another in the imago state. This is the case with the whole Order _Lepidoptera_, which in the former eat plants chiefly, in the latter nothing but honey or the sweet juices of fruit, which they have often been observed to imbibe; and the same rule obtains also in regard to most dipterous and hymenopterous insects. Those which eat one kind of food in both states, are chiefly of the remaining orders.

I have said that insects, like other animals, draw their subsistence from the vegetable or animal kingdoms. But I ought not to omit noticing that some authors have conceived that several species feed upon mineral substances[715]. Not to dwell upon Barchewitz's idle tale of East Indian ants which eat iron[716], or on the stone-eating caterpillars recorded in the Memoirs of the French Academy[717], which are now known to erode the walls on which they are found, solely for the purpose of forming their cocoons; Reaumur and Swammerdam have both stated the food of the larvæ of _Ephemeræ_ to be earth, that being the only substance ever found in their stomachs and intestines, which are filled with it. This supposition, which if correct renders invalid the definition by which Mirbel (and my friend Dr. Alderson of Hull long before him) proposed to distinguish the animal and vegetable kingdoms, is certainly not inadmissible; for, though we might not be inclined to give much weight to Father Paulian's history of a flint-eater who digested flints and stone[718], the testimony of Humboldt seems to prove that the human race is capable of drawing nutriment from earth, which, if the odious Ottomaques can digest and assimilate, may doubtless afford support to the larvæ of Ephemeræ. Yet after all it is perhaps more probable that these insects feed on the decaying vegetable matter intermixed with the earth in which they reside, from which after being swallowed it is extracted by the action of the stomach: like the sand that, from being found in a similar situation, Borelli erroneously supposed to be the food of many _Testacea_, though in fact a mere extraneous substance.

The majority of insects, either imbibing their food in a liquid state, or feeding on succulent substances, require no aqueous fluid for diluting it. Water, however, is essential to bees, ants, and some other tribes, which drink it with avidity; as well as in warm climates to many _Lepidoptera_, which are there chiefly taken in court yards, near the margins of drains, &c. Even some larvæ which feed upon juicy leaves have been observed to swallow drops of dew; and one of them (_Odenestis potatoria_), which (according to Goedart) after drinking lifts up its head like a hen, has received its name from this circumstance. That it is not the mere want of succulency in the food which induces the necessity of drink, is plain from those larvæ which live entirely on substances so dry that it is almost unaccountable whence the juices of their body are derived. The grub of an Anobium will feed for months upon a chair that has been baking before the fire for half a century, and from which even the chemist's retort could scarcely extract a drop of moisture; and will yet have its body as well filled with fluids as that of a leaf-fed caterpillar.

By far the greater part of insects always feed themselves. The young however of those which live in societies, as the hive- and humble-bees, wasps, ants, &c. are fed by the older inhabitants of the community, which also frequently feed each other. Many of these last insects are distinguished from the majority of their race, which live from day to day and take no thought for the morrow, by the circumstance of storing up food. Of those which feed themselves, the larger proportion have imposed upon them the task of providing for their own wants; but the tribe of Spheges, wild bees, and some others, are furnished in the larva state by the parent insect with a supply of food sufficient for their consumption until they have attained maturity.

As to their _time_ of feeding, insects may be divided into three great classes: the day-feeders, the night-feeders, and those which feed indifferently at all times. You have been apt to think, I dare say, that when the sun's warmer beams have waked the insect youth, and

"Ten thousand forms, ten thousand different tribes, People the blaze,"

you see before you the whole insect world. You are not aware that a host as numerous shun the glare of day, and, like the votaries of fashion, rise not from their couch until their more vulgar brethren have retired to rest. While the painted butterfly, the "fervent bees," and the quivering nations of flies, which sport

"Thick in yon stream of light, a thousand ways, Upward and downward thwarting and convolved,"

love to bask in the sun's brightest rays, and search for their food amidst his noon-tide fervor, an immense multitude stir not before the sober time of twilight, and eat only when night has overshadowed the earth. Then only, the vast tribe of moths quit their hiding-places; "the shard-born[719] beetle with his drowsy hum," accompanied by numerous others of his order, sallies forth; the airy gnat-flies institute their dances; and the solitary spider stretches his net. All these retire into concealment at the approach of light.--Some few larvæ (_Agrotis exclamationis_, &c.) have similar habits, and those of one singular genus before adverted to (_Nycterobius_) are remarkable for providing in the night a store of food which they consume in the day; but to the generality of these the period of feeding is indifferent, and most of them seem to eat with little intermission night and day.

Insects like other animals take in their food by the mouth (in _Chermes_ and _Coccus_, indeed, the rostrum seems to be, but really is not, inserted in the breast, between the fore-legs), but there is one exception to this rule. The singular _Uropoda vegetans_, which is such a plague to some beetles, derives its nutriment from them by means of a filiform pedicle or umbilical cord attached to its anus; and what increases the singularity, sometimes several of these mites form a kind of chain, of which the first only is fixed by its pedicle to the beetle, each of the remainder being similarly connected with the one that precedes it; so that the nutriment drawn from the beetle passes to the last through the bodies and umbilical cords of the individuals which are intermediate[721]. Some have regarded these bodies as true eggs; and their analogy with the pedunculated eggs of _Trombidium aquaticum_, which also seem to derive nourishment from the water-boatmen, &c. to which they are fixed, and still more the circumstance of their ultimately losing their pedicle and detaching themselves from the infested beetles, give plausibility to the idea. Yet these animals are certainly furnished with feet, and have according to De Geer[722] a part resembling a mouth--characters which cannot be attributed to any egg.

In the variety of their instruments of nutrition, which you must bear in mind are often quite different in the larva and perfect states, insects leave all other animals far behind. In common with them, a vast number (the orders _Coleoptera_, _Hymenoptera_, and _Orthoptera_, and the larvæ of _Lepidoptera_, some _Diptera_, &c.) are furnished with jaws, but of very different constructions, and all admirably adapted for their intended services; some sharp, and armed with spines and branches for tearing flesh; others hooked for seizing, and at the same time hollow for suction; some calculated like shears for gnawing leaves; others more resembling grindstones, of a strength and solidity sufficient to reduce the hardest wood to powder: and this singularity attends the major part of these insects, that they possess in fact two pairs of jaws, an upper and an under pair, both placed horizontally, not vertically, the former apparently in most cases for the seizure and mastication of their prey; the latter, when hooked, for retaining and tearing, while the upper comminute it previously to its being swallowed[723].

To the remainder of the class of insects, a mighty host, jaws would have been useless. Their refined liquid food requires instruments of a different construction, and with these they are profusely furnished. The innumerable tribes of moths and butterflies eat nothing but the honey secreted in the nectaries of flowers, which are frequently situated at the bottom of a tube of great length. They are accordingly provided with an organ exquisitely fitted for its office--a slender tubular tongue, more or less long, sometimes not shorter than three inches, but spirally convoluted when at rest, like the main spring of a watch, into a convenient compass. This tongue, which they have the power of instantly unrolling, they dart into the bottom of a flower, and, as through a siphon, draw up a supply of the delicious nectar on which they feed. A letter would scarcely suffice for describing fully the admirable structure of this organ. I must content myself therefore with here briefly observing that it is of a cartilaginous substance, and apparently composed of a series of innumerable rings, which, to be capable of such rapid convolution, must be moved by an equal number of distinct muscles; and that, though seemingly simple, it is in fact composed of three distinct tubes, the two lateral ones cylindrical and entire, intended, as Reaumur thinks, for the reception of air; and the intermediate one, through which alone the honey is conveyed, nearly square, and formed of two separate grooves projecting from the lateral tubes; which grooves, by means of a most curious apparatus of hooks like those in the laminæ of a feather, inosculate into each other, and can be either united into an air-tight canal, or be instantly separated, at the pleasure of the insect[724].

Another numerous race, the whole of the order _Hemiptera_, abstract the juices of plants or of animals by means of an instrument of a construction altogether different--a hollow grooved beak, often jointed, and containing three bristle-formed lancets, which, at the same time that they pierce the food, apply to each other so accurately as to form one air-tight tube, through which the little animals suck up[725] their repast; thus, forming a pump, which, more effective than ours, digs the well from which it draws the fluid[726].

A third description of insects, those of the order _Diptera_, comprising the whole tribe of flies, have a sucker formed on the same general plan as that last described, but of a much more complicated and varied structure. It is in like manner composed of a grooved case and several included lancets; but the case, although horny, rigid and beak-like in some, is in others fleshy, flexible, and more resembling the proboscis of an elephant, and terminates in two turgid liplets: and the accompanying lancets are themselves included in an upper hollow case, in connexion with which they probably compose an air-tight tube for suction. The number and form of these instruments is extremely various. In some genera (_Musca_) there is but one, which resembles a sharp lancet. Others (_Empis_, _Asilus_,) have three, the two lateral ones needle-shaped, that in the middle like a scymetar; together forming so keen an apparatus, that De Geer has seen an Asilus pierce with it the elytra of a lady-bird; and I have myself caught them with not only an _Elater_ and weevil, but even a _Hister_ in their mouths. In many horse-flies we find four; two precisely resembling lancets, and two, even to the very handles, buck-hafted carving-knives[727]. The blood-thirsty gnat has five, some acutely lanced at the extremity, and others serrated on one side. The flea, the spider, the scorpion have all instruments for taking their food of a construction altogether different[728]. But it is impossible here to attempt even a sketch of the variations in these organs which take place in the apterous genera, and in many of the dipterous larvæ. Suffice it to say that they all manifest the most consummate skill in their adaptation to the purposes of the insects which are provided with them, and which can often employ them not only as instruments for preparing food, but as weapons of offence and defence, as tools in the building of their nests, and even as feet.

Some insects in their perfect state, though furnished with organs of feeding, make no use of them, and consume no food whatever. Of this description are the moth which proceeds from the silk-worm, and several others of the same order; the different species of gad-flies, and the Ephemeræ, insects whose history is so well known as to afford a moral or a simile to those most ignorant of natural history. All these live so short a time in the perfect state as to need no food. Indeed it may be laid down as a general rule, that almost all insects in this state eat much less than in that of larvæ. The voracious caterpillar when transformed into a butterfly needs only a small quantity of honey; and the gluttonous maggot, when become a fly, contents itself with a drop or two of any sweet liquid.

While in the state of larvæ the quantity of food consumed by insects is vastly greater in proportion to their bulk than that required by larger animals. Many caterpillars eat daily twice their weight of leaves, which is as if an ox, weighing sixty stone, were to devour every twenty-four hours three quarters of a ton of grass--a power of stomach which our graziers may thank their stars that their oxen are not endowed with. A probable proximate cause for this voracity in the case of herbivorous larvæ has been assigned by John Hunter, who attributes it to the circumstance of their stomach not having the power of dissolving the vegetable matters received into it, but merely of extracting from them a juice[729]. This is proved both by their excrement, which consists of coiled-up and hardened particles of leaf, that being put into water expand like tea; and by the great proportion which the excrement bears to the quantity of food consumed. From experiments, with a detail of which he has favoured me, made by Colonel Machell on the caterpillars of _Euprepia Caja_, he ascertained that, though a larva weighing thirty-six grains voided every twelve hours from fifteen to eighteen grains weight of excrement, it did not increase in weight in the same period more than one or two grains. On the other hand, many carnivorous larvæ increase in weight in full proportion to the food consumed, and that in an astonishing degree. Redi found that the maggots of flesh-flies, of which one day, twenty-five or thirty did not weigh above a grain, the next weighed seven grains each; having thus in twenty-four hours become about two hundred times heavier than before[730].

Some insects have the faculty of sustaining a long abstinence from all kinds of food. This seems to depend upon the nature of their habits. If the insect feeds on a substance of a deficiency of which there is not much probability, as on vegetables, &c. it commonly requires a frequent supply. If, on the contrary, it is an insect of prey, and exposed to the danger of being long deprived of its food, it is often endowed with a power of fasting, which would be incredible but for the numerous facts by which it is authenticated. The ant-lion will exist without the smallest supply of food, apparently uninjured, for six months; though, when it can get it, it will devour daily an insect of its own size. Vaillant, whose authority may be here taken, assures us that he kept a spider without food under a sealed glass for ten months, at the end of which time, though shrunk in size, it was as vigorous as ever[731]. And Mr. Baker, so well known for his microscopical discoveries, states that he kept a darkling beetle (_Blaps mortisaga_) alive for three years without food of any kind[732]. Some insects, not of a predaceous description, are gifted with a similar power of abstinence. Leeuwenhoek tells us that a mite, which he had gummed alive to the point of a needle and placed before his microscope, lived in that situation eleven weeks[733].

In some cases the very want of food, however paradoxical the proposition, seems actually to be a mean of prolonging the life of insects. At least one such instance has fallen under my own observation. The aphidivorous flies, such as _Syrphus Pyrastri_, &c. live in the larva state ten or twelve days, in the pupa state about a fortnight, and as perfect insects sometimes possibly as long--the whole term of their existence in summer not exceeding at the very utmost six weeks. But one[734], which I put under a glass on the 2d of June, 1811, when about half grown, and, after supplying it with Aphides once or twice, by accident forgot, I found to my great astonishment alive three months after; and it actually lived until the June following without a particle of food. It had therefore existed in the larva state more than eight times as long as it would have lived in all its states, if it had regularly undergone its metamorphoses--which is as extraordinary a prolongation of life as if a man were to live 560 years. It is true that its existence was not worth having even to the larva of a fly. For the last eight months it remained without motion, attached by its posterior pair of tubercles to the paper on which it was placed, manifesting no other symptoms of life than by moving the fore part of the body when touched, and replacing itself on its belly if turned upon its back. But this was quite enough to prove it still alive.--I can attribute this singular result to no other circumstance than its having been deprived of a sufficient quantity of food to bring it into the pupa state, though provided with enough for the attainment of nearly its full growth as larva. Possibly the same remote cause might act in this case, as operates to prolong the term of existence of annual plants that have been prevented from perfecting their seed; and it would almost seem to favour the hypothesis of some physiologists, who contend that every organised being has a certain portion of irritability originally imparted to it, and that its life will be long or short as this is slowly or rapidly excited--no great consolation this for the advocates for fast-living, unless they are in good earnest in their affected preference of a "short life and a merry one:" though it must be admitted that they would have the best of the argument were the alternative such a state of torpid insensibility as that with which our larva purchased the prolongation of its existence.

* * * * *

After this general view of the food of insects, and of circumstances connected with it, I proceed to give you an account of some peculiarities in their modes of procuring it.

The vegetable feeders have for the most part but little difficulty in supplying their wants. In the larva state they generally find themselves placed by the parent insect upon the very plant or substance which is to nourish them: and in their perfect state their wings or feet afford a ready conveyance to the banquet to which by an unerring sense they are directed. All nature lies before them, and it is only when their numbers are extraordinarily increased, or in consequence of some unusual destruction of their appropriate aliment, that they perish for want. The description of their food renders unnecessary those artifices to which many of the carnivorous insects are obliged to have recourse: and none of them, if we except the white-ants, whose cunning mode of insinuating themselves into houses in tropical climates has been detailed in a former letter, can be said to use stratagem in obtaining their food.

Of the carnivorous species, the greater proportion attack their prey by open violence, such as the predaceous beetles, the Ichneumons, burrowing wasps, and true wasps; the praying insects (_Mantis_); the bugs (_Geocorisæ_ Latr.); dragon-flies (_Libellulina_), &c.; which have been before adverted to. But a very considerable number, chiefly, however, of one tribe, that of spiders, provide their sustenance solely by artifice and stratagem, the singularity of which, and the admirable adaptation of the instruments by which they take their prey to the end in view, afford a most wonderful instance of the power and wisdom of the Creator, and have attracted admiration in all ages. A description of these, however, which will require a detailed survey, I must refer to another letter.

I am, &c.

FOOTNOTES:

[703] _Ephem. German. An._ xii. _Obs._ 58. Rai. _Hist. Ins._ 261.

[704] _Linn. Trans._ xi. 11. _t._ 3. _f._ 5-7.

[705] De Geer, iv. 210.

[706] Brahm, _Insekten Kalender_, i. 190.

[707] Reaum. iv. 280.

[708] De Geer, vi. 112.

[709] Reaum. vi. 271.

[710] _Entomologische Bemerkungen_ (Braunschweig 1799), p. 6.

[711] Latreille, _Obs. sur les Hymenoptères_. _Ann. de Mus._ xiv. 412.

[712] Reaum. iii. 257.

[713] Ibid. iii. 277.

[714] Ibid. ii. 324.

[715] For an instance in which an insect, usually subsisting upon animal food, derived nutriment from a mineral substance, see _Philos. Magaz._ &c. for January 1823. 2--.

[716] Lesser, _L._ i. 259.

[717] x. 458.

[718] _Dictionnaire Physique._

[719] In the controversy between the commentators on Shakespeare, as to whether _shard_[720] means wing-cases, dung, or a fragment of earthenware, and whether _born_ should be spelled with or without the _e_, it might have thrown some weight into the scale of those who contend for the orthography adopted above, and that the meaning of _shard_ in this place is dung, if they had been aware that the beetle (_Geotrupes stercorarius_) is actually _born_ amongst dung, and no where else; and that no beetle which makes a hum in flying can with propriety be said, as Dr. Johnson has interpreted the epithet in his Dictionary, "to be born amongst broken stones or pots." That Shakespeare alluded to the Beetle, and not to the Cockchafer (_Melolontha vulgaris_), seems clear from the fact of the former being to be heard in all places almost every fine evening in the summer, while the latter is common only in particular districts, and at one period of the year. S.

[720] _Sharn_ is the common name of cow-dung in the North: therefore Shakespeare probably wrote _sharn_-born. _Mr. MacLeay._

[721] De Geer, vii. 123.

[722] Id. ibid. 126.

[723] PLATE VI. FIG. 4, 5. 10, 11. 24-26.

[724] For a full description of this instrument see Reaum. i. 125, &c. PLATE VI. FIG. 13.

[725] The mode, however, in which this is effected in all insects furnished with a proboscis, can scarcely be by suction, strictly so called, or the abstraction of air, since the air-vessels of insects do not communicate with their mouths: it is more probably performed in part by capillary attraction; and, as Lamarck has suggested, (_Syst. des Anim. sans Vertèbres_, p. 193.) in part by a succession of undulations and contractions of the sides of the organ.

[726] PLATE VI. FIG. 16-19.

[727] PLATE VII. FIG. 5.

[728] PLATE VII. FIG. 8. 10.

[729] _Obs. on the Animal Œconomy_, p. 221. Compare Reaum. ii. 167.

[730] Redi _de Insectis_, 39.

[731] _New Travels_, i. xxxix.

[732] _Phil. Trans._ 1740, p. 441. I confess, notwithstanding Mr. Baker's general accuracy, that I suspect some mistake here.

[733] Leeuw. _Op._ ii. 363.

[734] Not having ever met with another specimen, I am unable to say of what precise species of aphidivorous fly it is the larva, nor can I find a figure of it, though it approaches near to one given by De Geer (vi. _t._ 7. _f._ 1-3). Its shape is oblong-oval, length about four lines, and colour pale red speckled with black. Each of the seven or eight segments which compose the body projects on each side into three serrated flat aculei or teeth; three or four similar but smaller aculei arm the head: and two, much larger than the rest, the anus, one on each side of the usual bifid protuberance which bears the respiratory plates. A bifid tubercular elevation is also placed in the middle of the back of each segment.