Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/206

 PEA

PEA

live at their utmofl fize. About the 15th of May they are in a condition to lay, and as the eggs are discharged, the belly is pufhed clofer and clofer to the back ; and when all are laid, becomes the fhell before defcribed, and the young ones are hatched under it, and become full of eggs, and do the fame office afterwards to their young.

One great difficulty, however, is to conceive by what means they are fecundated : fome have imagined them each to be male and female in the fame individual, and hermaphrodites of a very Angular kind ; for as in fiiails, worms, and (bine other in lefts, which are both male and female in the fame in- dividual, there flill is the congrefs of another animal of the fame fpecies required for propagation ; in thefe it mould feem, on the contrary, that one alone was fufficient. Others ima gine them males and females, as other animals, and that they perform thefe offices during the three or four firft days after they are hatched, while they are running on the branches. Had thefe obfervers known that the animals were in a condi- tion to move during all the winter months, that is during the greater part of their lives, they would not have been re- duced to the improbable conjecture of their performing this office as foon as produced : the truth is, however, that it is not known that they do it at all, thefe obfervers never having feen the thing, but only judging it an indifpenfible neceffity ; but a clofe obfervation will furnifli grounds for an opinion of another kind.

In the end of April the branches of the peach and other trees covered with thefe infefts, will be found to be greatly fre- quented by a fort of fmall flies, beautiful enough'to demand attention : their head, breafl, body, and legs are all of a deep red ; they have only two wings, but thofe very large, being nearly twice as long as their bodies : thefe, in the fly's com- mon poflure, are crofled on the back, and the upper almofl entirely hides the under one; they are lefs tranfparent than thofe of the common flies, and are of a dufky white, b rdered with an edge of a fine bright and beautiful red : but what chiefly diflinguifhes them from all other fpecies is, that they have two long white threads which run from their hinder part, and are of twice the length of their wings; between thefe there is alfo a remarkable part, a fort of tail made like a piercer, and of a third or fourth part of the length of thefe threads. This is like. all other flings, thicker at its bafe than at its point, and is bent a little downwards. The antennas of this fly are adorned with long bodies, hairy, and larger at their extremities than at their infertions on the antennae. It is eafy at firft fight to conceive, that thefe are the flies that had been produced of worms fed in the bodies of the gall-infects of a former year, and that they were now fearching an opportunity to depofit their eggs in the bodies of thefe little creatures, to be hatched into worms there, and thence to come out in flies, as they themfelves before had done.

The piercer at their tails made this the more probable, as it feemed to refer them to the ichneumon clafs ; but a clofer at- tention to the whole progrefs of thefe infefts will give much more room to believe, that thefe flies are the male gall-infers. They are, indeed, very fmall in proportion to the females, but this will give the judicious naturalift no caufe to doubt their being the males of the fame fpecies, any more than their hav- ing wingsand the females not; fince the fame difference and difproportion is found in beetles and many other infefts; the colour of their juices, when crufhed, and their fmell, are in both exaftly the fame. And another obfervation adds great- ly to the probability, which is, that many branches of the peach-tree are fo loaded with the young gall-infers that have newly fixed themfelves, that one would wonder what muft become of them when they fwell in bulk, as there could be no room for their growth on the branch on which they already flood fo clofe as to touch one another.

But examining thefe branches afterwards, at the feafon when thefe flies appear, multitudes of thefe gall-infecls are found converted into mere {hells, out of which fometbing has efcap- ed and gone ; and thefe are fo compleat, and feem to have been quitted in fo very different a manner from the broken fpoils of the female ga'l-injecls, that there is all the probability in the world of thefe flies having been let out of them, which had before lain there in the form of nymphs : feveral of thefe, in the very irate of nymphs, Mr. Reaumur found in thefe fliells ; and the whole remaining queftion is, whether thefe were the proper animal, or whether they were owing to the egg of fome fly accidentally depofited there, and hatched in the~body of the animal. The former, however, feemed on all confe- derations to be the mere probable opinion ; for no obfervation at a proper feafon will tver fhew a living worm in the body of the gall-infe£t ; and the manner of the fly's egrefs is not that of thefe unnaturd births, which are always by a hole made by the fly ; but the fhell in this cafe readily opens at a proper feafon, and lets out the fly, by parting all round at the com- miflure of the belly and back, which feems too natural for any thing but the very manner deflined for the produdion of the proper fpecies.

The flies examined on the branches with a g'afs will alfo be

found to introduce this feeming piercer always at the fame

. place into the body of the gall -in, cfl, and this is that cleft in

the hinder part of the body, out of which the young ones when hatched, afterwards find their way. The flies, which lodge their eggs or young worms in the bodies orother infefts, if crufhed at that feafon, will be always found to contain fuch eggs or fmall worms ; and the microfcope never fails to dis- cover them in the matter crufhed out of flics even i'maller than thefe, but in thefe no obfervation ever fhews any fuch. See Tab. of Infefts, N y 29

Notwithflandi-g that the feack-gall-irfeR is the only fpecies in which the male fly has been obferved, there is no room to doubt but that the othtr fpe les ?1I have males of the fame kind. The orange ga/l-ivfecl has been obferved not univerfally fe- cundated, but that there is only a part of the animals that lays eggs ; probably the others are thole which hatch into the male flies : and the kermes, the nobleff and 1:10ft valuable of all the gall-in'etls, is known often to produce a white winged fly, very like that of the feath-gall-infeR. And Brennius, who gave fome time fince a hiflory of the fcaihr grain of Poland, the c ecus PolonUus, a kind of frc-gall h?fcl ; tho' in the fiift account he gave into the opinion of both fexes being included in each of thefe animals, and that each was in itfelf fufficient for the propagation of its fpecies : yet afterwards, to his very great honour, he added an account of his' having difcovered the male of this fpecits, which he defcribes to be a fmall fly, with a red body and white wings bordered with red; a fly in all refpefts like the male of the peach- gall-infcdi. Thefe flie?, carefully examined, and prefled gently on their belly, andjat the fame time obferved with a good microfcope, will be feen to thruft out of the part which r-fembles the piercer of the ichneumon race, a fine, flender and foft white thread. Were this in reality the fame with the piercers of the ichneumons, this part mnft have been hard and horny, to be able to enter hard fubflances ; on the contrary, it is ever found foft and flefhy, and is undcubtedly no piercer, but the organ of generation in the male infeft.

it is much to be doubted, whether the gal!-infef1s y in form of a boat inverted, are not the fame fpecies living on different trees : this is certain, that the animal taken from one trte will live and multiply on another ; and the diflinftions between the fpecies, even fo different in their maturity, are often not eafy while the animals are young, the boat-fafhioned, the orbicu- lar, and the reniform being not diflinguifhable till the time they acquire the greatefl fize, and with that lize, this their na- tural figure. The gall-infecls of the hazel and lime, which are of the half-round kind of the peach, and the perfeftly orbi- cular one of the oak, are all inflances of this; and all be- tween the time of their being a fimple fiat body, and their acquiring an orbicular or partly orbicular figure, aflume one much like that of the boat-fafhioned ones. Reaumur's Hift. Inf. Tom. IV. p. 1, to 44.

PEANTIDES, the name of a fione to which the antients at- tributed great virtues for promoting delivery, Thefe ffones were found in Macedonia and other places; and all the defcription we have of them is, that they refembled wa- ter congealed by frofl. Probably the antients meant by this name the jlalacl'itts, or flony icicles, which, as they hang from the roofs of caverns, greatly refemble the drcpnings of water from the eves of houfes congealed in frofty weather.

PEARCH, perca, in ichthyology. See Perca.

Pe arc H-glae, in mechanics, the name of a kind of glue, of a remarkable ftrength and purity, the manufacture of which we owe to the Laplanders, from whom SchefFer has defcribed it. They take a number of large pearches, and flitting them open, they carefully pick away the flefli with a knife, fo as to leave the fkin pure. They put a number of thefe (kins into a vefl'el of warm water, which they expofe to the fun, and by that means keep it in a continual moderate heat for feveral days; when the fcales become loofe by this maceration, they take out the fkins and rub them clean off". The foft and clean fkin then remains alone, and feels as foft as a wetted bladder. 1 hefe clean flans they throw into a fmall quantity of frefh water, and boil them gently over the fire, flirring the whole together, and toward the end beating it forcibly with little flicks. The fkins by this means at length wholly diilblve in the water, and the whole becomes a thick tranfparent liquor j which, when boiled as long as the thicknefs of it will permit, without burning, they pour out on a flat flone, and as it cools they cut it into cakes exaftly refembling our glue, but that they want the coarfe reddiih colour it has, and have no dif- agreeable fmell. When they would ufe this, they diflblve it in more water, exaftly as we du our glue. The bows of this people give us a very great proof of the flrengtfi of this fort of glue : they are made of two pieces fattened together with it, and tho' put to the moft forcible trials, as thefe people are very flrong, and ufe them in (hooting bears, rain-deer, &c. yet the glue part is never known to ftart, Sd-cjfer's Hiff. Lapland.

PEAR, pyus y In botany. See the article Pyrus.

All the forts of fea>s propagated in gardens, are produced by budding, or grafting them upon flocks of their own kind; which are commonly called tree-jiochs, or elfe upon the quince or whitethorn flocks ; but the laft are now generally difufed, the fruit produced this way being apt to be dry and mealy. 'I he quince-flocks are, however, in great cileem 2 for