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doubled, the creature enters it, there to fuffer its deftin'd change. In this cafe, however, the covering it has made ferves it not only for a lodging, but alfo for food ; for fo long as it finds it neceflary to eat, it may feed upon the walls of its caftle, in a prudent manner, not devouring too haftily, for all may be eaten away, except the outer one of all, which is of itfelf alone fuffirient for the purpofe. It is probable, that every caterpillar who makes a cafe of this kind, makes it of a fumcient number of turns, or doubles, to ferve the neceflary calls of its future hunger, and, in many of the fmaller kinds, the ftrcngth of the whole is little or nothing impaired by their eating, iincc they eat only the parenchymatous fubftance of the leaves, without touching the ribs, which are the main ftrength and fupport of the whole.
Befide thefc caterpillars, which in this manner roll up the leaves of plants, there are other fpecies which only bend them once, and others which, by means of thin threads, connect many leaves together to make them a cafe. All this is a very furprizing work, but all much inferior to this method of rol- ling.
The different fpecies of caterpillars have different inclinations, not only in their fpinning, and their choice of food, but even in their manners and behaviour one to another. They are all hatched from the eggs of butterflies, many fpecies of which always depofit a great number of eggs on the fame place. Thefe all hatcli very nearly at the fame time, and it would be very natural to fuppofe, that the young brood, in all the fpecies, fhould be enclined to continue and live to- gether. But this is not the cafe, the different fpecies have their different inclinations, and conduct themfelves always in in the fame kind by the fame ftated rules. Some never part company from the time of their being hatch'd to their Lift change, but live and feed together, and undergo together their laft change into the chryfalis ftate. Others feparate one from another as foon as able to crawl about, and each hunts its fortune fingle ; and there are others which regularly live to a certain time of their lives in community, and then feparate each to fbift for itfelf, and never to meet again in that ftate. Thofe which live wholly together, begin by forming a line, with their little bodies, upon a leaf, their heads ftanding all regularly even, and in this manner they move and eat toge- ther ; and often there are feveral ranges of this fort, which jnake fo many phalanxes, in an order as regular as the military one, and eat into the leaf they ftand on with perfect equa- lity.
This is the cafe with many, while young, which, when they grow larger, firft make one common habitation, furrounded by a web, which is the joint work of them all, and within which there is a peculiar neft of every one, of its own fpinning, When they have made this common lodging, they feparate, and each takes its courfe over the tree, or bum, for food, well knowing where they are all to meet. In this man- ner, many hundreds of thefe animals form a fort of re- public, where every thing is carried on in perfect order and regularity, and the feparate cell of each, in the general habi- tation, is finally the place where it is to pafs, in tranquillity, its change into the chryfalis ftate. There arc other fpecies of caterpillars which do not feparate from one another, even for thefc neceflary occafions of feeding, and their transformation: Thefe live their whole time together, and are ufually found in their ftate of chryfalis all huddled together, and their cafes fre- quently flicking to one another, and numbers of them making only one confufed mafs.
There is one thing yet to be obferved, in regard to the cuftoms and manners of thefe little animals, this is the regu- larity of their marches. Nothing can produce an union be- tween a number of fubjects, fo well as an abfolute obedience to fome one chief; and this is regularly obferved by thefe communities of caterpillars. When they have occafion to change their quarters, one of their number, who feems to have the fole power and direction of the rout, marches fingly firft whichever way he pleafes. He is followed by two others, who keep their bodies very nicely in the fame di- rection with his, and, after thefe, there follows a large party ; thefc regulate their motions by the former, and fo the order is continued through the whole company. When the leader turns to the right, or to the left, the whole body is immediately fecn to do the fame ; when he ftops, they all immediately flop, and march again the moment that he begins to advance. This chief feems, however, to be no particular favourite, nor to have any lafting power, but it feems mere chance that confti- tutes him in hispoft. This, however, is always certain, that while he is in power, the reft are perfectly obedient. Reau- mur, Hift. Inf. T. 2.
Caterpillars are very deftructive and pernicious in gardens, particularly thofe of two fpecies. The one of thefe is that which afterwards becomes the common white butterfly. This is of a yellowifli colour, fpotted with black, and infefts the leaves of cabbages, cauliflowers, and the Indian crefs, of which it eats off all the tender parts, leaving only the fibres entire, fo that whole plantations are often feen deftroyed by them in autumn, efpecially fuch as are near large buildings, or are crouded with trees. There is no remedy againfl this evil, but the pulling the creatures off before they are fpread
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from their nefts, and watching the butterflies, which -.are daily, in the hot weather, depofiting their eggs on thefe plants. Thefe, however, feed principally on ihi outfide of the leaves of the plants, and are therefore the'eafier taken off; but the other kind lives near the center, and therefore is with much more difficulty difcovered. This is much larger, and the ikin is very tough, and of a brown colour. It is called, by the gardeners, a grub, and is extreamly pernicious. The eggs which produce it are ufually depofited in the very heart, or cen- ter, of the^ plant, particularly in cabbages, and the creature, when form'd, and grown to fome fize, eats its way through all the leaves, and leaves its dung in great quantity behind ft, which fpoils the cabbage. This infaS alfo burrows nnder the furface of the ground, and makes fad havock-among young plants, by eating off their tender -/hanks, and drawine' them into the holes. This mifchief is chiefly done in the night; but wherever a plant is feen thus deftroyed, if the earth be ftirred with a finger an inch deep, the creature will be cer- tainly found, and this is the only way of deftroying them, Miller's Gardner's Dia.
When thefe infefts attack fruit trees, the beft method of driving them off is this ; boil together a quantity of rue, wormwood, and the common tobacco, of each equal parts, in common water ; make the liquor very ftrong, and fprinkle it on the leaves and young branches every night and morning, during the time when the fruit is ripening. Munting, de Plant.
Eruck Aquatics:; Water Caterpillars. — It might feem incre- dible that there is any fuch creature as a caterpillar, whofe natural habitation is under water ; but experience and obser- vation prove that there are fuch, and that they feed on the water plants as regularly as the common kinds do on thofe at land. Thefe are not named at random, like many of 'the aquatic animals of the larger kinds, the fea wolf, and the fea horfe, (sfc. which might as well be called any thing elfe as wolves and horfes, but they are properly what they are called, and do not refpire in the manner of the fifh tribe, but by their ftigmata, as other caterpillars. Mr. Reaumur, in his obfer- vations, met with two fpecies of thefe, the one upon the potamogiton, or pond-weed, the other upon the lenticula, or duckmeat. Thefe are both very induftrious animals ; but the firft being much the larger, its operations are more eafily diitinguifhed.
This, though truly an aquatic animal, fwims but badly, and does not at all love to wet itfelf. The parent butterfly lays her egg on a leaf of the potamogiton, and, as foon as the young caterpillar is hatched, it gnaws out a piece of the leaf of a roundifli (hape. This it carries to another part of the fame leaf, and lays it in fuch a manner, that there may be a hollow between, in which it may lodge. It then faftens down this piece to the larger leaf with iilk of its own fpinning, only leaving certain holes at which it can put out its head, and get to gnaw any of the leaves that are near. It eafily gets out, though the aperture be naturally final], fince a little force from its body bends up the upper leaf, and bends down the lower, both being flexile, and when the creature is out, it has a fort of down that defends itfelf from being wetted, and the natural elafticity of the leaves, and of the filk, join the aperture up again, fo that no water can get in. The leaves of this kind of plant are alfo naturally very flippery, and not eafily wetted by water. It foon happens, that this habitation becomes too fmall for the animal, in which cafe it makes juft fuch another, and after that, at times, feveral others, each being only made fit for it at the fize it is then of. The changes of this creature into the chryfalis and butterfly ftate, are in the common method. The butterfly gets out of a chry- falis which was placed on the furface of the water, the light- nefs of the animal eafily fuftains it on the water till its wines are dried, and it then leaves that element never to return tolt again. Mem. Acad. Par. 1736.
Erucje Syhejires, Wood Caterpillars, See Wood.
Eruca, Rocket, in botany, the name of a genus of plants, the characters of which are thefe : The flower confifts of four leaves, and is of the cruciform kind. The piftil arifes from the cup, and becomes, at length, a pod, divided into two cells by an intermediate membrane, and ufually containing roundifh feeds. To thefe marks it is to be added, that all the plants of this genus have the fame peculiar tafte. The fpecies of Rochtt, enumerated by Mr. Tournefort, are thefe: 1. The broad-leav'd white flowered garden Rochtt.
2. The garden Rochtt, with leaves divided into fegments.
3. The broad-leav'd, narrow podded Rochtt, called the Rochtt gentle, or Roman Rochtt. 4. The daify-leav'd Rochtt. 5. The fine leav'd perennial yellow flower'd Rochtt. 6. The great yellow Rochtt, with rough ftalks. 7. The fmaller yellow wild Rochtt, with fhepherd's purfe leaves. 8. The Indian tawny-leav'd Rochtt. Tourn. Inft. p. 226.
ERUCAGO, in botany, the name of a genus" of plants, of which there is only one known fpeeies. The characters of this are thefe : The flower confifts of four leaves, difpofed in form of a crofs j and the piftil arifes from the cup, and af- terwards becomes a remarkable pod, of the (hape of a fquare club, which is divided into four cells, and contains roundifli 3 and
