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quor as limpid and clear as that of the anus. This ttands in round drops at the end of one or both of them at once, and refembles heads upon pins. This liquor, tho' limpid in fome fpecies, is, however, reddifh and thick in others; as particu- larly in thofe of the willow : and as this feems plainly to be an excrement, the creature is very Angular in having its dif- ferent paffages for thofe of different kinds. The liquor void- ed by the aperture at the extremity of the body, which re fembles the anus in other animals, appearing to be the urine ; and this by thefe two horns, the feces of the bowels. At any time when there is not a drop to be feen upon either of the horns, if the body of the animal be gently fqueezed, a drop will always be forced out either from one or both. The puceron, like moll other infects, changes its fkin three or four times before it arrives at its full growth. Thefe exuvije perfectly refernble the animal in its natural fiate, the legs and other parts being all in their proper places; but whatever is the colour of the fpecies of puceron, thefe flans which it caffs are whitifli. They lie in great numbers about the leaves where the creatures are, and among them there is ufually found a cottony matter. p This at firft fight might be miftaken for the fkins, reduced to a kind of powder ; but on a clofer examination, it appears to be truly filamentous, and on a nice infpeclion is found to be the natural produce of many fpecies of the animal. All thofe kinds of pucerons which are not fmooth and gloffy, as if varnifbed, have more or lefs of this cottony matter about them : in fomz the whole rough nefs of the furface is made of it; and in pthers, it ftands in white fpots on feveral parts of the body.
Thofe pucerons which inhabit the bladders or leaf-galls of the elm and other trees, and thofe which live in the folded leaves of the black poplar, are all of the nature of thofe which pro- duce the laigett fhare of this matter: they have it hanging in long filings in an odd manner from their bodies, and often are fo compleatly covered with it, that they look as if they had been wetted, and then rolled in meal.
On examining the leaves of fomc plants and trees inhabited by thefe animals, there is feen a fort of collection of this down into parcels, fo that they refernble the white feathers of a bird in miniature. The leaves of the beech-tree afford thefe plumes in the greatett perfection, and frequently they cover its leaves in whole clutters, and are an inch or more in length. Thefe plumes, or clutters of plumes, feem all to grow out of the leaf, and are much thicker at their bafe than at their ex- tremity ; a great number of the plumes that compofe them be- ing fhorter than the rett, and not running to the extremity The longer plumes divide themfelves into two clutters near their origin, and thefe never unite again afterwards; when examined by the microfcope, each plume appears to be com- pofed of feveral other plumes or threads, like thofe of cotton, ■which are undulated, but not twitted together. Tho' thefe clutters of plumes feem to be fixed to the leaf, yet when more clofely examined, that is found not to be at all the cafe ; but that they really proceed from the body of a puceron. The different threads or plumes arife from the different parts of the body of the animal, and altogether they hide it absolutely from fight as it ftands on the leaf. When the bottom of the tufts are examined, however, there are always found either the bo- dies of the pucerons, or their exuvias; for when they quit their fkins, they quit thefe filaments with them. Tho' thefe long threads might feem a confiderable load for fo fmall an animal, yet when the creature is touched it always moves very brifldy, and as it creeps along, generally leaves fome of its plumes in the way; but in its motion, no other part of it than the head, and the foremoft pair of legs are feen. Reaumur's Hift. Inf. Vol. VI. p. 53.
The young brood of this fpecies are green, and only by de- grees acquire this white down ; which at firtt appears only in form of a farinaceous powder, and by degrees lengthens out as we fee it. The old ones alfo, when they have newly changed their fkins, have it not at all ; and when it after- wards grows upon them, it is by thefe degrees, and in this manner. The leaves of the common bramble alfo afford this remarkable fpecies of puceron; and the common meadow crow- foot is frequently covered with clutters of them at its lower part, refembling a white mould'tnefs. The filaments that co- ver the bodies of this fpecies of puceron, are not at all of the nature of the filky matter fpun by other animals; but feem to be produced from every pore of the body, and to ifi'ue thence in form of fmall round globules of a liquid matter, which harden with the air, and adhering to one another as they iffue out, form this fort of plume, a congeries of which make the tufts we fee. The male and female pucerons, as they are ufually fuppofed to be, differ greatly from one another in form, even in their time of growing; but much more eminently at the time of their maturity, the male having then wings, which the fe- males never have. Lewenhoek and others, who have treated of thefe animals, have fuppofed that they all became at length little flies, that is, were winged ; hut this is a great error. The young male pucerons may be dittin^uifhed from the fe- males by having a fort of eminence on their fhoulders, of a fqnare form ; which is owing to the young wings. The fe- veral changes of the fkin which thefe animals have, make no
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great difference in their form till the laft, when the mates ap- pear wtth their Wings at liberty. A little before this laft cafb ■ng oft the (kins the males are feen to have a fort of tuber- oiity alfo on each fide, which is owing to the win<*s folded up there within the &in ; but the females, tho' nnfch larger than thefe, have no fucb protuberance. '
The winged pucerons, when they have caft off their laft (kin, and have their wings loofe, do not, however, fhew them immediately ; for they are folded clofely together, and the crea- ture then appears like what it was before, being all over green and having only two eminences on the fide : but In a quarter of an hour, the head and fhoulders change from their ,-reen colour to a fine Alining black, and the wings unfold an3 ex- pand themfelves, and then cover a large part of the body, and extend themfelves to a confiderable length beyond it. Thefe now appear animals wholly different from what they were before, and many of the flies which we fee in our gar- dens are ot this kind : the animal, however, tho' it appear fo very different from its fellow infects, is much more like them when clofely examined, than could be imagined. It Kill car- ries the great character of the genus, which is the having two horns growing out from the hinder part of the body, and dill has "ts trunk, and lives by lucking the juices of plants. Reau- mur's Hift. In!. Vol. VI. p. 57.
Notwithftanding, however, the general opinion, that the winged pucerons are all males, and the unwino-ed ones females it appears that their manner of generation is°yet unknown to* us. This opinion was founded too haftily by f ome f rom a luppofed analogy of thefe and other infects ; but later obfer- vatlons prove, that this is not ftricfly the cafe I for that the winged ones, as well as the others, bring forth young ones, borne have fuppofed, that thefe winged and naked «mn were the offspring of different families of feveral fpecies liv- ing together; but the contrary is proved by this that the winted ones are found to produce fome winged and fome naked ones ; and the naked to produce both kinds in the fame manner. Some have imagined, that they found the male tu- cerons among the others, obferving fome of a (latter fhape, in whofe bodies there were never found any young ones as there always were in the others, even when they°were very young ; but thefe have been fincc found to be only fuch fe- males as had already brought forth their offspring. The young pucerons being" themfelves filled with embryos, and that in every individual, fo that all that have been ever examin- ed appear mothers, has given many ftrangc ideas of the man- ner of their generation: many have imagined them all to be hermaphrodites ; and as no copulation has ever been obferved among them, they are by fome fuppofed to be able to impreg- nate each itfelf. The later opinion, however, is, that when a female is once impregnated by a male, (he will brino- forth young ones already impregnated with others, and thus°to the third or fourth fuccefiion ; fo that copulation is only necefiaiy to thefe animals once in three or four generations, and the children and chiklrens children of an old puceron that has had congrefs with a male, will bring forth young ones without having ever had any fuch congrefs. Reaumur's Hift. Inf. Vol. VI. p. 59. See the articles Wood -puceron, 0,\K-lm- ceron, &c. Bladder Puceron, a fort of puceron that lives in bladders on the leaves of trees. See Puceron, fupra.
We often obferve on the leaves of different trees, a fort of roundifh bladders, which only adhere to the leaf by a fhort I pedicle : thefe are a fort of fmall galls, and their figure varies much in the different kinds ; fome are lefs round than others, and many are very rough on the furface ; and fometimes they are long, terminating in a point, and being broader at the bafe than in any other part, and fuftained by no pedicle, but fixed immediately to the leaves.
The elm and aft afford us more frequent inftances of thefe than any other trees, and very often on the firft of thefe they grow to the bignefs of a nut, and fometimes much lar°er ; and when they are grown to their full (fee, they often take up the whole furface of the leaf. When thefe bladders are open- ed, they are found to contain a large number of pucerons. If thefe bladders are examined at the time when they are but newly rifen, which ufually is in the beginning of June, on opening them there is ufually found in them only one puceron, and that always a female big with young; and in others more advanced, the parent infect is found furrounded with differ- ent numbers of her young ones. Thefe bladders have all of them at firft only one female puceron ; but afterwards they have more, as they become larger ; and the largeft of all are ufually found filled with a prodigious number of younfr ones. The newly rifen bladders are always found' clofe and°firm in every part, the aperture at which the female puceron had entered, being ufually neatly and clofely flopped up. The queftion is' how this bladder was formed ?
We very well know, that winged infefls of feveral kinds prick holes in the leaves and branches of vegetables, and de- pofit their eggs in them ; and that thence arife all the various fpecies of galls, the eggs hatching within thofe tumors into worms or maggots, and thefe finally becoming winged infects like their parents. Malpighi has given an excellent account of the feveral fpecies
