« ZurückWeiter »
Account of the Insefls called Aphides, and Remarks on the Natural Hiflory of the Bee. By George Adams.
THE habits of the Pucerons are so very singular, that I cannot pass them over in silence; the more to, as they are a very curious object for the microscope. They are called by various names, the proper one is aphis; that vFhich they are most known by is puceron, though they are sometimes called virie-fretters and plantlice. They belong to the hemiptera order. The rostrum is inflected, the antennæ are longer than the thorax, feme have four erect wings, others have none at all: towards the end of the belly there are two tubes, from which is ejected that most delicate juice called honey-dew.
The aphides arc a very numerous genus. Linnæus has enumerated thirty-three different species, whose trivial names are taken from the plant which they inhabit, though it is probable the number is much larger, as the fame plant is often found to support two or three different sorts of aphides.
An aphis, or puceron, brought up in the most perfect solitude from the very moment of its birth, in a few days will be found in the midst of a numerous family: repeat the experiment on one of the individuals of this family, and you will sind this second generation wiHmultiply like its parent,
and this you may pursue through many generations.'
Mr Bonnet had repeated experw ments of this kind, as far as the sixth generation, which all uniformly pre^ semed the observer with fruitful vir< gins, when he was engaged in a series of new and tedious experiments, front a suspicion imparted by Mr Tremb'ey in a letter to him, who thus expresses himself: "I have formed the design "of rearing several generations of solU "tary pucerons, in order to fee if they "would all equally bring forth young.' "In cafes so remote from usual dr-* M cumslanecs, it is allowed to try all "sons of means; and I argued with "myself, who knows but that one "copulation might serve for several "generations?" This "*uho bio-vis" persuaded Mr Bonnet that he had not sufficiently pursued his investigations. He therefore now reared to the tenth generation his solitary aphides, having the patience to keep an exact account of the days and hours of the birth of each generation. He then discovered both males and females among them, whose amours were not in the least equivocal; the males are produced only in the tenth generation, and are but few in number; that these
soon arriving at their full growth, copulate) • EJpys on the Microscope} lately published. •
pulate with the females, and that the virtue of this copulation serves for ten successive generations; that all these generations, except the first, from fecundated eggs, are produced viviparous, and all the individuals are females, except those of the last generation, among whom some malts appeal to lay the foundation of a frelh series.
- Ift Order, to give a further insight into the nature of these insects, I shall insert an extract of a description os the different generations of them by Dr Richardson, as published in the Philosophical Transactions, vol. lxi.
"The great variety of species which occur in the insects now under consideration, may make an inquiry into their particular natures seem not a little perplexing; but by reducing them tinder their proper genus, the difficulty is considerably diminished. We may reasonably suppose all the insects, comprehended under any distinct genus, to partake of one general nature; and by diligently examining any particular species, may thence gain some insight into the nature of all the rest. With this view Dr Richardlon chose out of the various forts of aphides the largest of those found on the rose-tree, not only ds its size makes it more conspicuous, but as there are few others of fe long a duration. This fort appears early in the Spring, and continues late in the Autumn; while several are lij Baited to a much shorter term, in conformity to the different trees and plants from whence they draw their nourishment.
I. If at the beginning of February the weather happens to be so warm as to make the buds of the rose-tree swell and appear green, small aphides are frequently to be found on them, tho' not larger than the young ones in Summer, when Cist produced. It will be found, that those aphides which ap
Eear only in Spring, proceed from small, lack oval eggs, which were depoliced •a the Lst year's ihust; though When,
it happens that the insect mslfei to* early an appearance, the greater part suffer from the sharp weather that usually succeeds; by which means, the rose-trees are some years in a manner freed from them. The fame kind of animal is then at one time of the year viviparous, and at another oviparous.
Those aphides which stand the ieverity of the weather seldom come to their full growth before the month of April, at which time they usually begin to breed, after twice casting off their exuvia, or outward covering. It appears that they are all females, which produce each of them a numerous pro-' geny, and that without having intercourse with any male insect; they ara viviparous, and what is equally singular, the young ones all Come into theworld backwards^ When they first come from the parent, they aie enve* loped by a thin membrane, having in this situation the appearance of an oval egg ; these egg-like appearances adhere by one extremity to the mother, while the young ones contained in them extend the other, by that means gradually drawing the ruptwed membrane over the Mead and body to the hind feet. During this operation, and for some time after, the fore pan of the head adheres, by means of something glutinous, to the vent of the parent. Being thus suspended in the air, it soon' frees itself from die membrane in which it was confined ; and after its limbs are. a little strengthened, is set down on some tender shoots, and left to provide for itself.
In the Spring months there appear on the rose-trees but two generations of aphides, including those which proceed immediately from the last year's eggs; the warmth of the Summer adds so much to their senility, that no les» than five generations succeed one another in the interval One is produced in May, which cast* off its covering j while the months of June and July each supply two' more, which cast Oh their coverings three or four times, according according to the different warmth of khc season. This frequent change of tlieir outward coat is die more extraordinary, because it is repeated more often when the infects come the soonpit to their growth, which sometimes happvus in ten days, where warmth and plenty of nourishment conspired.
Early in the month of June, soms of the third generation which were produced .about .the middle of May, after casting off their Ia.it Covering, discover four erect wings much longer than their budies; ynd the smie is observable in all the succeeding gcncialioos which arc produced during ths Sunnier months, but itil 1 without any diversity ot sex ; for some time before the aphides come to their full growth, it is easy to distinguish which will have wiugs, by a remarkable fullness of the breast,, which in the others is hardly to be distinguished from the body. When the [alt covering is rejected, the wings, which were before folded up in a very narrow compass, ire gradually extended in a very surprizing manner, till their dimensions arc at last very considerable.
Tfre increase of dies; insects in the Snmmei time is ib very great, that by wounding and exhausting the tender moots they would' ficquently suppress all vegetation,-had they not many eoemies to restrain them. Notwithstanding these insects have a numerous lri.be of enemies, they are not without friends, if those may be considered as 'luca, who arc officious in their attendance for the good things they expect to reap thereby. The ant and the bee are of this kind, collecting the honey in which the aphides abound, but with this difference, that the ants are constant visitors, the bee only when flowers ;;re scarce; the ants will fuck ia ths,honey while the aphides are in the act of discharging it; the bees only collect it from the leaves on which it has fallen
• la the Autumn three more geneMtions of the aphides ar? produced, frjfoi. VII. No 30. 'C
two of which generally make their appearance in the month of August, and the third before the"middle of September. The two first differ in no respect from those which arc found in Summer; but the diird differs grcutljf from all the reft. Tho' all the aphides which have hitherto appeared were females, in this tenth generation several male infects are found, but not by any means so numerous as the females.
The females have at first die lame appearance with those of the former generations, but in a few days their colour changes from a green to a yellow, which is gradually converted into an orange bsfore they come to their full growth; they differ also in another reipect from those which occur in Summer, for all these yellow females are without wings. The male; infects are, however, still more re-; markaule, their outward appearanca .readily distinguishing them from thia and all other generations. When first produced, they are not of a green colour like the rest, but of a reddish brown, and have afterwards a dark, line along the back; they come tos, their full growth in about three weekr, and then cast off their last covering, the whole insect being after this of"* bright yellow colour, the wings onlyexcepted j but after this change to 3. deeper yellow, and in a very few horns' to a dark brown, if we except the body, which is something lighter coloured, and has a reddilh cast. The male* no sooner come to maturity than they copulate with the females, who in i. day or two after their intercourse with. the males lay their eggs, generally near the buds. Where there are a number crowded together, they of course, interfere with each other, in which they will frequently deposit their egg* on other parts of the branches.
It is highly probable that the aphides derive considerable advantages by living in society; the reiterated punctures of a great number of them may attract a larger quantity osnuu:ti-' c ous 200
Natural History osth Bee.
ous juices to that part of the tree, or plant, where they have taken up their abode.
In the natural history of insects, new objects of surprize are continually rising before the observer: singular as ■we have already shewn is the production of the Puceron, that of the Bee will not be found to be less so; and though this little republic has at all times gained universal esteem and admiration, though they have attracted the attention of the most ingenious and laborious inquirers into nature, Vet the mode of propagating their species seems to have baffled the ingenuity of ages, and rendered their attempts to discover it abortive ; even the labours and scrupulous attention of Swammerdam were unsuccessful; though, while he was Writing his treatise on bees, his daily labour began at six in the morning, arid from that hour' till twelve he continued watching their Operations, his head in a manner dissolving into sweat, under the irresistible ardour of the sun j and if he desisted at noon, it was only because his eyes then became too weafc, as well from the extraordinary afflux of light and the use of glasses, to continue longer exercised by Atch minute objects. He spent one month entirely in examining, describing, and repfe* fenting their intestines; and many months on other parts: employing -whole days in making observations, and whole nights in registering them, till at last he brought his treatise of bees to the wilhed-for perfection; a work which all the ages,' from the Commencement of natural history to our own times, have produced nothing to equal, nothing to Compare with it. ** Read it, fays the great Boerhaave, consider it, and then judge for yourself." Reaumur, however, thought he had in some measure removed the veil, and explained their manner of generating: he supposes the queen-bec to be the only female injhc hive, -;.J
the mother of the next generation j that the drones are the males, by which flic is fecundated: and that the working bees, or those that collect wax on the flowers, that knead it, and form from it the eombs and cells, which they afterwards fill with honey, are of neither sex. The queen-bee is known by its size, being generally much larger than the working-bee of the drone
Mr Schirach, a German naturalist, affirms, that all the common bees ate females in disguise, in which the organs' that distinguish the sex, and particularly the ovaria, are obliterated, or at least from their extreme minuteness have escaped the observer's eye; that every one of those bees, in the earlier period of its existence, is capable of becoming a queen bee, if the whole community should think it proper to nurse it in a particular manner, and raise it to that rank: in short, that the queen bee lays only two kinds of eggs, those that are to produce (he drones, and those from which the working bees are to proceed.
Mr Schirach made his experiments not only in the early Spring months, but even as late as November. He cut off from an old hive a piece of the brood-comb, t.iking care that it contained worms which had been hatched about three days. He fixed this ia an empty hive, together with a piece of honey-comb, for food to his becsj and then introduced a number of com* mon bees into the hive. As soon as these found themselves deprived of their queen and their liberty, a dreadful Uproar took place, which lasted for the space of twenty-four hours. On the cessation of this tumult they betook themselves to work, first proceeding to the conduction of a royal cell, and then taking the proper methods /or feeding and hatching the brood inclosed with them; sometimes even on the second day the foundation of one or more royal cells were to be perceived ; die view of which furnished cer
Natural Uisiory os the Bee.
tain indications that they had elected one of the inclosed worms to the sovereignty. The bees may now be left at liberty.
The final result of these experiments is, that the colony of working bees being thus lhut up with a model of brood-comb, not only hatch, but at the end of eighteen or twenty days produce fromthence one or two queens, which have.to all appearance proceeded from worms of the common fort, which appears to have been converted by them into a queen, merely because they wanted one.
From experiments of the fame kind, riried and often repeated, Mr Shirach concludes that all the common working bees were originally of the female sex; but fhai if they are not fed, lodged, and brought up in a particular manner while they arc in a larva state, their organs are not developed; and that it is to this circumstance attending the bringing up of the queen, that the extension os the female organs is effected, and the difference in her form and size produced.
Mr Debraw has carried the subject further, by discovering the impregnation of the eggs by the males, and the difference 6T the size among the drones ot males; though indeed this last circumstance was not unknown to Mess. Maraldi and Reaumur. Mr Debraw watched the glass hives with indefatigable attention, from the moment the bees, among which he took care there should be a large number of drones, were put into them, to the queen's laying her eggs, which generally happens the fourth or fifth day; he observed, that on the first or second day (always before the third) from the time the eggs are placed in the cells, a great number of bees fastening themselves to one another hung down in the form of a curtain, from the top to the bottom of the hive; they had done the lame at the time the queen deposited her eggs, an operation which . seems contrived on purpose to conceal what is transacting: however, through
some parts of this veil he was enabled to fee some of the bees inserting the posterior part of their bodies each into a cell, and sinking into, but continuing there only a little while. When they had retired, it was easy to discover a whitish liquor left in the angle of the basis of each cell, which contained an egg. In a day or two this liquor was absorbed into the embryo, which on the fourth day assumes its worn* or larva state, to which the working bees bring a little honey for nourishment, during the first eight or ten days after its birth. When the bees find the worm has attained its full growth, they leave off bringing it food, they know it has no more need of it; they have still, however, another service to pay it, in which they never sail, it is that of shutting it up in its cell, where the larva is inclosed for eight or ten days: here a further change takes place ;*the larva, which was herctefore idle, now begins to work, and lines its cell with fine silk, while the working-bees inclose it exteriorly with a wax coveting. The concealed larva then voids its excrement, quits its skin, and assumes the pupa; at the end of some days the young bee acquires sufficient strength to quit the (lender covering of the pupa, tear the wax covering of its cell, and proceeds a perfect infect.
To prove further that the eggs are fecundated by the males, and that their presence is necessary at the time of breeding, Mr Debraw made the following experiments. They consist in leaving in a hive the queen, with only the common or working bees, without any drones, to see whether the eggs lhe laid would be prolific. To this end, he took a swarm, and shook all the bees into a tub of water, leaving them there till they were quite senseless; by which means he could distinguish the drones, without any danger of being stung: he then restored the queen and working-bees to their former state, by spreading them on a brown paper ia the sun; after c 2 - fliia