Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/380

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them in a train, twenty or more, at fmall diftances, in a ftrait line before one another ; but if ftie finds the branch become lefs proper for her purpofe after fhe has laid three or four, fhe leaves it and feeks out another, where fhe finifhes what fhe had there begun. There is not any apparent dif- ference in the feveral young branches of the fame rcfe tree, that can fhew us why one is, and another is not proper for this purpofe ; but the creature herfelf is very curious in her choice, and ufually examines a great number before fhe fixes upon a proper one. The operation might feem very difficult to fo fmall an animal ; but though the creature be of a very fluggifh difpofition, in all refpects, it feems to find no trou- ble in this, and will ufually finifh the laying fix eggs in this manner in half an hour. The apertures are Co fmall, that there are ufually about fifteen of them in the fpace of an inch, and yet there is always a fmall fpace between each, and thofe above and below it. On ft ripping, the baik from one of thefe branches, the wounds are feen to enter into the wood, and refemble fo many openings of a vein, by a furgeon in blood letting. In each of thefe there is depofited one egg, which is confiderably large, of a yellow co- lour, and pointed at one end. If the branch of a rofe tree, in which the eggs of this infect are thus depofited, be exa- mined from time to time afterwards, the part where they are placed will be found to change colour, the bark will turn brown and then black, and the wounded parts will elevate themfelves above the reft of the furface, and refemble a firing of beads, or a long chain of olives. This elevation of the wounded parts is not to be attributed to the growth of them j but they are, on the contrary, fo far deftroyed, as to be rendered incapable of increafe that way. This fwel- ling is owing to another very fingular caufe ? which per- haps nature does not give us another inltance of in the whole animal world. The egg daily increafes in fize after it is laid, and this is very evidently feen on opening the feveral lodgments, formed at different times ; thofe which have been made two or three days, al- ways containing eggs more than twice as large as thofe made within a few hours. It is to be obferved, in fa- vour of this ftrange occurrence, that the egg of this creature is not covered with a hard fhell in the manner of a bird's egg ; but only with a thin, and eafily diftenfible mem- brane ; but then all other eggs of infects are in the fame manner covered with a diftenfible membrane, not a hard fhell, and yet none of them are ever known to increafe in fize after their being laid. The egg, in thus increafing in fize, raifes up the wood and the bark which cover it ; and in confequence of this, the train of eggs make a firing of regular elevations of the part, as the egg increafes, and the tumor grows larger ; the aperture at the furface grows alfo wider in proportion, fo that the worm, when hatched out of it, finds no difficulty in getting out, but immediately crawls to the leaves and begins eating.

There is, befide this fpecies, another fly of the fame genus, produced from a baftard caterpillar of the rofe tree, and of the fame Ihape and ftruclure of parts with this, but differing in colour : the head and breaft of this fiy are of a deep violet colour, the body is yellow, and the legs and wings are of a fomewhat paler violet tinge. This creature alfo depofites its eggs in holes, made in the branches of the rofe tree, by means of a double faw placed at the hinder part of the body ; but, as the former fpecies lays them in a fingle ftrait line, this difpofes them in a very beautiful and very regular manner in two rows. Two eggs are firft laid by the creature, at fome fmall diftance, fideways, one from another, but at the fame height of the branch. The bottoms of thefe meet almoft one with the other ; hut their tops are expanded a little, fo that they make an acute angle, or exprefs the fhape of the letter V ; behind thefe there are placed two others, making a fomewhat wider angle, and fo behind thefe two others. Thus the creature frequently depofits ten, twelve, or four- teen pah of eggs, which are all placed at fome fmall diftance from one another, and are feparatcd into two diftindt rows by an intermediate line, Thefe are not fo well defended from injuries as the eggs of the former fpecies, and are entirely buried in the wood ; and lodged in fuch laro-e holes, that they appear naked even when firft laid Mr. Vallifnieri, who has elegantly defcribed this infect, obferves, that as the faws of the former fpecies are toothed only on one fide, having a fiat back in the manner of our common faws, thofe of this fpecies are toot bed both ways he obferves alfo, that the two pieces which make a cafe for thefe faws, and which are opened to give them paflage when they are to be ufed, are each of them hollow, and are of the greateft ufe to the creature ; the one ferving as the paflage for the eggs, the other for that of the glutinous iiquor with which the creature covers the wound in the wood, after depofiting her egg in it. But Mr. Reaumur, in comparing the fize oT the egg, when new laid, with the aperture, which -this au- thor fuppofes it to be depofited through, is of opinion that it is much too large to have gone through fuch a paflage ; he alfo obferves, that the eggs may always be forced" out of the body by preffing it between the fingers j but

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that, in 'this cafe, they are always feen iffuing out at the anus.

The rofe tree feems the peculiar favourite of thefe forts o flies, for befide the two fpecies already defcribed, there is another very fmall one which is found on this tree in great abundance in the months of April and May. This is every way ftaped like the large kinds, but it is all over black except fome white fpots on the legs ; the faw of this fmall infect is not of a fufficient ftrength to penetrate the branches of this fhru'b, it therefore always is feen upon the leaves, and depofits its little eggs in a row of holes made in the middle rib of a leaf. . It is to be obferved that all the falfe or baftard caterpillars produce thefe ferrated flies ; yet it is very fingular that they do not all make the fame apparent ufe of their faws that thefe do. The fly produced by the falfe caterpillar of the goofeberry, always depofits its eggs in fingle rows along the middle ribs of the leaves ; but the eggs are not let into them by holes made for that purpofe, but are merely laid along upon the furface. It may be however, that the creature makes a wound where every egg is to be depofited, which though not large enough to receive it, may yet fuffice to afford a neceflary moifture to it. Mr. Reaumur was at the pains to keep fome of the falfe caterpillars produced from the eggs of this fly the whole feafon, and obferve them through all their changes. When they had eaten fufficiently in the caterpillar ftate, they crept into the earth which he had put into the bottom of his boxes, and then changed into cnryfalifes in a double covering of a filky matter of their own lpinning ; they remained all the win- ter in this ftate, and in the fucceeding fpring came forth out of the earth in form, of flies. This author obferves, that on putting a male and female together into another box, in which there were fome branches of goofeberry bullies, the female immediately fearched out the proper places for de- pofiting her eggs, and laid feveral before his face in fingle rows on the molt prominent part of the ribs of the leaves : the creature feemed to give herfelf all the motions that the other fpecies do in piercing the branches of the rofe tree, before the depofiting of every egg ; but that on examining the places afterwards, he never could find any mark of a wound in them, the eggs all lay upon the furface, but they were fo firmly fixed on the place, that there was no remov- ing them without breaking them, and a piece of the fkin was always left behind, which ftuck raft on the place and covered the hole if there was any. There are alfo fome other fpecies of thefe flies, which make no apparent ufe of the curious faws they have behind : yet they all are poffeffed of them. Reaumur's Hift. Inf. Vol. 9. p. 160. See the article Serrate Flies. Rose galls, in natural hiftory, a name given by authors to certain unnatural productions of the rcfa fylvejiris, or dog rofe, occafioned by the bites of infecls : there are two kinds of thefe, the one very common, the other more rare. The fcarcer kind is ufually found on the young (hoots, and on the heps or fruit, and is of a woody fubftance ; the other is hairy and fpungy and is found on the old branches. The woody kind ufually appears in the months of June and July, and is always found in clutters. Thefe are compofed often, twelve, or more galls of different fizes and figures, fome round, others oblong, fome of the fisse of an olive, and others not larger than a pea. They are of the com- mon fubftance of the white wood or blea of trees, and when fituated on the fruit they prevent its ripening and make a very fingular figure. They are of a reddifh colour and are ufually fmooth and glolfy, but fometimes they are befet withfhort and fine prickles.

The hairy rofe gall is too common, and too fingular a figure to have efcaped the obfervation of perfons in all ages; it has been introduced into medicine in many parts of the world, and is at this time prefcribed in Germany, when reduced to powder, in diarrhoeas, dyfenteries and other dis- orders of the bowels, and to promote urine and break the ftone. Thefe rofe galls, though they appear at firft fight com- pofed of tufts of hair, are however in reality made up of feveral fmall galls growing from a bud on the branch and forming a clufter on the part. They are of an oblong fi- gure and refemble the fhape of a plum-ftone. Each of them is the habitation of a finale worm, each having one cell in the center. This is perfectly fmooth and even on the infide, but from the outer furface of each of thefe feparate galls there go off a vaft number of filaments which uniting and intermingling with one another form one com- plex mafs, and give the whole clufter the figure of one gall of the bignefs of an Indian or horfe chefnut. Thefe fi- laments are of a reddifh or grecnifh colour, and are often nearly an inch in length. They are called by fome hairs, but very improperly, having no true character of a hair, but being of a rough furface, flatted, and branched with feveral fhorter filaments growing from their fides. The tuber- cles within, from which thefe grow, are of a hardnefs greater than that of molt fpecies of wood. Though thefe galls are ufually iound on the branches of the fhiub, and arifing from the buds or eyes of young fhoots, and are therefore fuppofed by authors to be die vitiated matter of a whole

branch.