Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/316

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wife than in extremely great numbers. In plants they fallen themfelves on every part) but in trees, ihey only feize upon the leaves and young (hoots, and they ufually cover thefe entirely, leaving no part to be feen. Reaumur's Hift. Inf. Vol. VI. p 13.

The elder is the tree on which they are of all others the molt plentifully produced, and on which they are obferved in their fevcral ftages with the greateft accuracy and cafe. They often cover the thick green roots of this tree for many inches to- gether, and fometimes for many feet ; and they are always placed fo clofe together, that they touch in every part, and fometimes they lie two beds, one over another. Thefe are of a gi eenifh black. If they are obferved on the branches un- difturbed, they are always found to be perfectly quiet, and feem to pafs their whole lives in inaction ; but they are all this time doing the moft neceffary bufmefs of life, that is, fucking in their nourifhment from the juices of the tree. They do this by means of a fine (lender trunk, which eafily efcapes the naked eye ; but is always found by the microfcope, and it is by means of this that they pierce the bark of the tender parts of the vegetables, and get at their juices. The trunk is ufually of two thirds of the length of the body ; but when they are moving on, it is always applied fo clofely under the belly, that it isnotfeen.

When there are two fcries of thefe infects placed one over ano ther, they are always more loony placed in the upper feries, and thefe are ufually the larger and the nimbler in all their motions. In this cafe they have no power of fucking the plant ; for befide that it is clofe covered with the other feries, their trunks are not long enough to reach and penetrate it from the heighth at which they Hand above it. Thefe, therefore, are fuch as have no farther need of nourifhment, but are em- ployed in propagating their fpecies. Mr.De la Hire thought, that when thefe animals arrived at their winged ftate, they laid eggs on the ftalks and leaves of thofe plants on which we find them afterwards hatched without wings. The reafon of his fuppofing this, was doubtlefs the opinion of an analogy be- tween thefe creatures, and the butterflies and flies, with the other animals of the winged clafs : but obfervation and facts agree but very ill with that analogy ; for if the plants on which they abound be obferved nicely from day to day, their numbers will be found daily to increafe on the leaves and branches, and this without the leaft appearance of eggs : on the other hand, as the new-produced animals are of very dif- ferent fizes, this fpeaks their being of different ages; and from hence it appears evident, that they are not produced in the manner of other infects, which, when perfect, have wings ; but, on the contrary, that they are really produced alive from the parent. Mr. Reaumur raw them brought forth ; and, indeed, the obfervations of Mr. Lewenhoek long before, made it evident that this was the cafe ; for he faw, by the help of microfcopes, the young animals perfectly formed, tho' ex- tremely minute, in the bodies of the full-grown females. If the large and full-grown pucerofis are watched on their na- tive places, with moderately powerful magnifiers, there will foon be feen fome of them that have a fmall greenifh body Handing out from near the anus. This is the moft plainly vi- able in the elder puuron y which is itfclf ufually biackifh. This in its firft appearance is an oblong body, refembling an egg flatted a little ; but as it more nearly approaches to its delivery from the body of the parent, there appear legs upon it, and it is clearly feen to be a perfect and very lively animal. The legs by degrees fly off from the fides and belly, along which they were laid, and the creature then makes feveral motions to affift the getting out of its head from the body of the pa- rent ; for thefe infects are always brought into the world with the hinder part foremoft. The parent is wholly paflive all the time of the birth, all her efforts being internal ; fo that the body ftirs not out of its place, nor is the young one able to help itfelf till its whole body is very near out, as the legs are attached to the breaft at a fmall diftance from the head : and even when the head is out, the antennae require the repeated motion of the young one, for a minute or two, to feparate them.

The whole operation of the delivery of one young one ufually takes up about feven minutes. Mr. Reaumur obferved the de- livery of the pucertms of all kinds to be in the fame manner. He found it very eafy to make the obfervation, as the fe- male puurpis are eafily diftinguUhed from the male by their being much thicker in the body, and by their fkin feeming always much diftended, and by the furrows which feparate the rings of the body being obliterated. They are a fort of animal whkh propagates fo quickly, that ufually there are many fe- males on the fame leaf or branch of a plant in labour at the fame time ; and their fcecundity is fo great, that when they have once begun to bring forth young ones, they feem to con- tinue it inceffantly for a long time together. They will often bring forth fifteen or twenty fucceflively, and if their bodies be a little fqueezed afterwards, there are forced out of it a vaft number of others lefs mature ; yet even in thefe the eyes may be diftinguifhed: and after thefe, there follow long chains, as it were, of lefs perfect ones, which feem like the beads of a necklace, and are oblong, and much refemble eggs. Thefe young ones are of different maturity, therefore, in the

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bodies of the parent; and in that refemble the eggs in hens and other birds, they always growing to a proper ftute for ex- clufion in this manner, one after another: whereas, in the quadrupeds, which are viviparous, the young ones of the fame brood, if ever fo numerous, always grow to their ftate of maturity for the delivery together, and are all excluded at the fame period. The young pucerons, when firft brought forth, are always paler coloured than the parent; but are of the fame fhape and ftructure, except that their bodies are fomewhat flatted.

We fee that they are able to move their legs before they are perfectly excluded from the parent, and as foon as they are fo, they walk and feek a place where they may fix their little trunk into the plant, for the receiving nourifhment. This they always choofe to do as near to fome others of their fpecies as they can, always loving to live in communities. The young one always places its head as near as poflible to the hinder part of the next to it, and thus they obntinue enlarg- ing their bodies at every new birth. Thofe which live upon the leaves of trees and plants, always fix themfelves on the under fide, being there moft fhelrered ; and as their number is always Very great, they frequently much alter the plant whofe juices they fuck ; tho' fome fpecies, both of trees and plants, bear this much better than others. Id. ibid. p. 15. Thefe little infects are extremely plentiful on many different trees, and are very eafily obferved in their feveral ftages and progreffions by a curious fearcher after them ; but if at any time they are not fo eafily found, the perfon who feeks after them may be conducted to them by the ants, which he will find moving in great numbers on the trees and plants where they are, and pointing out the way to them Mr. Lewenhoek, Hartfoeker, and others, have obferved this, and have fuppofed that the ants fed on them, by their frequent- ing the places where they are found ; but that is far from be- ing the cafe, the ants, on the contrary, feem to love them as friends. Goedart judged better of the matter, and efteemed the ants of great benefit to the nation of pucerons^ in deftroy- ing many of their bloody enemies. Goedart, however, erred greatly in fuppofing the ants to be the mothers of the puceronsi yet this is an error that has place among our gardiners to this day, they all fuppofing that the ants leave a flime behind them, out of which, according to the opinion of this laft author, they judge them to be produced. We may, however, eafily find out the reafon of the ants following the clufters of puce- rom, without doing them any injury, when we confider that the ants love fugar and all fweet things, and the places about which the pu:erons are have ufually the cavities filled with a thick facchanne matter, formed of the juices of the plant, ex- travaf ited by the wounds they make in it, and dried up to this confiftence by the heat of the fun.

The bladders of the leaves of the elm always contain a large quantity of a faccharine juice ; but thofe of the black p-.jplar have always a much fweeter and more delicious fluid in them ; and very often on other trees, the extravafated faccharine juice may be feen among the clufters of thefe animals, and the ants crawling over their backs to feed upon it. This liquor of the elm has not efcaped the obfervation of the fearchers after remedies from the vegetable world ; but tho* great virtues have been attributed to it by many, none have yet given any true account of its origin. I he moft natural opinion would feem, that it was the juice of the tree fimply extravafated ; but experience fhews that it has another origin : it is really the excrement of thefe [.ucerons ; they receive no folid food into their bodies, all that is conveyed into them coming through their trunk, which is an extremely fine pipe; and as none but a very thin and pure juice can be received through fuch an organ, it is no wonder that the creature which lives wholly upon it fhould void no folid excrements. If a parcel of the puceron: be watched, it will not be long be- fore one or other of them will be found voiding a fmall round drop of this liquor by the anus, and after that, feveral more; which all falling upon one another, form the vifible drop on which the ants feed. The creature feems in fome pain on the voiding this, and very often the hinder legs may be obferved affifting in removing it from the anus.

Mr. Reaumur obferved, that it was common to find feveral drops of this liquor on the leaves of fome trees; and that, tho*' they were fluid and limpid, w!:en firft evacuated from the ani- mal, they became more and more thick afterwards, refembling honey after a few days, and after that drying up fo as not to be eafily removed from the leaves : and Mr. Geoftroy ob- ferved, that the liquor of the bladder of the elm became, when dried, as hard as the gum of the cherry-tree. The drops of this liquor is not fo frequently found on the leaves of plants as might be expected, and that becaufe many of them are im- mediately devoured by the ants, and many others are dried up by the fun ; but they may always be found collected in fome quantity in the bladders of the elm, and other trees inhabit- ed by thefe creatures, as there the liquor is defended from the heat of the fun, and is iafe from being devoured. Reaumur's Hift. Inf. Vol. VI. p. 49.

The two horns which are placed on the hinder part of the body of this infect are as Angular in their ufe as in their ap- pearance ; they are hollow, and they at times excrete alfo a li-

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