SILKWORM. The Silkworm has attracted so much attention in all civilized countries where it may be propagated - and raised for the silk which is obtained from the cocoons spun by the Iarvce, and especially in the United Stites, where much money has from time to time been spent in establishing this industry, that more than a passing notice is deemed necessary. There is no reason why the rearing of silkworms may- not be practiced in any portion of the United States south of 40', the only question being the eost of labor in attending thera. We believe the only two States where the industry is profitably carried on at present is in California and Kansas. The importance of the silk industry and the increasing demand for these products, as wealth increases, will undoubtedly prevent any glutting, of tbe market, since the price of silk fabrics has steadily increased for the last forty years until now the possession of real silk fabrics, unmixed with other material, for dresses is beyond the reach of any but the more wealthy. So impor tant was this industry considered that Dr. Riley was employed by the government of the United States to write a manual on the habits and rear ing of the worm and the puperation of the cocoons, and the food-plants of the worms, to which the reader is referred for information not contained in this article. From Dr. Riley's manual, we extract as follows: The Silkworm proper, or that which supplies the ordinary silk of eommerce, is the larva of a smali moth known to scientific men as ,•olearia ri. It is often popularly eharacterized as the Mulberry- Silk ivorm. Its place among insects is with the Le pidoptem , or Scaly-winged insects, family Bmiibyekbr, or Spinners. There are several elosely allied species. which spin silks of different qualities, none of wIdeli, however, unite strength and fineness in the same admirable proportions as does that of the mulberry species. The latter has, moreover, acquired many useful peculiarities during the long centuries of cultivation it has undergone. It has in fact become a true domes ticated animal. The quality which man has endeavored to seleet in breeding tbis insect is, of course, that of silk producing, and heuee we find that, when we compare it with its wild relations, the eocoon is vastly disproportionate to the size of the worm which makes it or the moth that issues from it. Other peculiarities have ineidentally appeared, and the great number of varieties or races of the Silkworm almost equals those of the domestic dog. The white color of the species; its seeming want of all desire to escape as long as it is kept supplied with leaves, and the loss of the power of flight on the part of the moth, are all undoubtedly the result of domestication. From these facts, and partieularly from that of the great variation within speeifie limits to which the insect is sub ject, it will be evident to all that the following remarks upon the nature of the Silkworm must necessarily be very general in their character. The r•ilkworm exists in four states—egg, larva, chrysalis, and adult or imago. The egg of the Silkworm moth is called by silk-raisers the seed. It is nearly round, slightly flattened, and in size resembles a turnip seed. Its color when first deposited is yellow, and this color it retains if unimpregnated. If impregnated, however, it soon acquires a gray, slate, lilac, violet, or even dark green hue, according to variety or breed. It also becomes indented. When diseased it assumes a still darker and dull tint. With some varieties it is fastened to the snbstance upon whieli it is deposited, by a gummy seeretion of the moth produced in the act of ovipositing. Other varieties, however, among which may be mentioned the Adrianople whites and the yellows from Nouka, in the Caucasus, have not this natural gum. As the hatching point approaelies, the egg becomes lighter in color, which is due to the fact that its fluid contents become con centrated, as it were, into the central, forming worm, leaving an intervening space between it and the shell, which is semi-transparent. Just before hatching, the worm within becoming more active, a slight elicking sound is frequently heard, which sound is, however, coinmon to the eggs of many other inseets. After the worm has made its exit by gnawing a hole through oue side of the shell, this last becoines quite white. Each female produces on an average from three to four hundred eggs, and one ounce of eggs contains about 40,000 individuals It has been noticed that the color of the albuminous fluid of the egg corresponds to that of the cocoon, so that when the fluid is white the cocoon produced is also white, and when yellow the eocoon again corresponds. The worm goes through from three to four molts or sicknesses, the latter being the normal number. The periods between these different molts are called ages, there being five of these ages including the first from the hatch ing and the last from the fourth molt to the spinning period. The time between each of these molts is usually divided as follows: The first period occupies from five to six days, the second but four or five, the third about tive, the fourth from five to six, and the fifth from eight to ten. These periods are not exact, but simply proportionate. The time erom the hatching to the spinning of the cocoons may, and does, vary all the way from thirty to forty days, depending upon the race of the worm, the quality of the food, mode of feeding, temperature, etc. ; but the same relative proportion of time between molts usually holds true. The color of the newly hatched worm is black or dark gray, and it is covered with long stiff hairs, which, upon close examination, will be found to spring from pale colored tubercles. Different shades of dark gray will, however, be found among worms hatching from the same batch of eggs. The hairs and tubercles are not noticeable after the first molt and the worm gradually gets lighter and lighter until, in the last age, it is of a cream-white color. When full grown it presents the appearance of Fig. 1. It never becomes entirely smooth, how ever, as there are short hairs along the sides, and very minute ones, not noticeable with the unaided eye, all over the body. The preparation for each molt requires from two to three days of fasting and rest, during which time the worm attaches itself firmly by the abdominal prolegs. In front of the first joint a dark triangular spot is at this time noticeable, indicating the growth of the new head; and when the term of sickness is over, the worm casts its old integument, rests a short time to recover strength, and then, fresh ened, supple, and hungry, goes to work feeding voraciously to compensate for lost time. This so-called sickness which preceded the molt was, in its turn, preceded by a most voracious appe tite, which served to stretch the skin. In the operation of molting, the new head is first dis engaged from the old skin, which is then grad ually worked back from segment to segment until entirely cast off. If the worm is feeble, or has met with any misfortune, the shriveled skin may remain on the end of the body, being held by the anal horn; in which case the indi vidual usually perishes in the course of time. It has been usually estimated that the worm in its growth consumes its own weight of leaves every day it feeds; but this is only an approxi mation. Yet it is certain that during the last few days before commencing to spin, it con sumes more than during the whole of its pre vious worm-existence. It is a curious fact, first noted by Quatrefages, that the color of the abdominal prolegs at this time corresponds with the color of the silk. Having attained full growth, the worm is ready to spin up. It shrinks somewhat in size, voids most of the excrement remaining in the alimentary canal; acquires a clear, translucent, often pinkish or amber-colored hue; becomes restless, ceases to feed, and throws out silken threads. The silk is elaborated in it, fluid condition in two long, slender, convoluted vessels, one upon each side of the alimentary canal. As these vessels approach the head they become less convoluted and more slender, and finally unite within the spinneret, from which the silk issues in a glutin ous state, and apparently in a single thread. The glutinous liquid which combines the two, and which hardens immediately on exposure to the air, may, however, be dissolved in warm water. The worm usually consumes from three to five days in the construction of the cocoon, and then passes in three days more, by a final molt, into the chrysalis state. The cocoon con sists of an outer lining of loose silk known as floss, which is used for carding, and is spun by the worm in first getting its bearings. The amount of this loose silk varies in different breeds. The inner cocoon is tough, strong, and compact, composed of a firm, continuous thread, which is, however, not wound in concentric circles, as might fairly be supposed, but irregularly, in short figure-of-eight loops, first in one place and then in another, so that in reeling, several yards of silk may be taken off without the cocoon turning round. In form the cocoon is usually
oval, and in color yellowish, but in both these features it varies greatly, being either pure silvery-white, cream or carneous green, and even roseate, and very often constricted in the middle. It has always been considered possible to distinguish the sex of the contained insect from the general shape of the cocoon, those con taining males being slender, depressed in the. middle, and pointed at both ends, while the female cocoons are of a larger size and rounder form, and resemble in shape a hen's egg with equal ends. The chrysalis is a brown, oval body, considerably less in size than the full grown worm. In the external integument may be traced folds corresponding with the abdomi nal rings, the wings folded over the breast, the antennce, and the eyes of the enclosed insect— the future moth. At the posterior end of the chrysalis, pushed closely up to the wall of the cocoon, is the last larval skin, compressed into a dry wad of wrinkled integument. The chrys alis state continues for from two to three weeks, when the skin bursts and the moth emerges. With no jaws, and confined within the narrow space of the cocoon, the moth finds some diffi culty in escaping. For this purpose it is pro vided, in two glands near the obsolete mouth, with a strongly alkaline liquid secretion with which it moistens the end of the cocoon, and dissolves the hard gummy lining. Then, by a forward and backward motion, the prisoner, with crimped and damp wings, gradually forces its way out, and when once out the wings soon expand and dry. The silken threads are simply pushed aside, but enough of them get broken in the process to render the cocoons, from which the moths escape, comparatively useless for reeling. The moth is of a cream color, with more or less distinct brownish markings across the wings. The males have broader antennm, or feelers, than the females. and may, by this fea ture, at once be distinguished. Neither sex flies, but the male is more active than the female. They couple soon after issuing, and in a short time the female begins depositing her eggs, whether they have been impregnated or not. Domestication has had the effect of producing numerous varieties of the Silkworm, every differ ent climate into which it has been carried having produced either some changes in the quality of the silk, or the shape or color of the cocoons; or else altered the habits of the worm. Some vari eties produce but one brood in a year, no matter how the eggs are manipulated; such are known as Annuals. Others, known as Bivoltins, hatch twice in the course of a year; the first time, as with the Annuals, in April or May, and the :.ec ond, eight or ten days after the eggs are laid by the first brood. The eggs of the second brood only are kept for the next year's crop, as those of the first brood always either hatch or die soon after being laid. The Trevoltins produce three annual generations. There are also Quadrivoltins, and in Bengal, a variety known as Dacey which is said to produce eight generations in the course of a year. Some varieties molt but three times instead of four, especially in warm countries and with Trevoltins. Experiments, taking into consideration the size of the cocoon, quality of silk, time occupied, hardiness, quantity ofleaves required. etc., have proved the Annuals to be more profitable than any of the polyvoltins, although Bivoltius are often reared; and Mr. Alfred Brewster, of San Gabriel, Cal., says that he found a green Japanese variety of these last more hardy than the Chinese Annuals. Varie ties are also known, by the color of the cocoons they produce, as Greens, or Whites, or Yellows, and also by the country in which they flourish. The white silk is most valuable in commmice, but the races producing yellow, cream-colored, or flesh-colored cocoons are generally considered to be the most vigorous. No classification of varieties can be attempted, as individuals of the same breed exported to a dozen different locali ties would, in all probability, soon present a dozen varieties. The three most marked and noted European varieties are the Milanese (Italian), breed, producing fine, small, yellow cocoons; the Ardeche (French), producing large yellow cocoons, and the Brousse (Turkish), producing large white cocoons of the best quality in Europe. Owing to the fearful preva lence of ptIbrine among the French and Italian races for fifteen or twenty years back, the Japanese Annuals have come into favor. The eggs are bought at Yokohama in September, and shipped during the winter. There are two prin cipal varieties in use, the one producing white and the other greenish cocoons, and known respectively as the White Japanese and the Green Japanese Annuals. These cocoons are by no means large, but the pods are solid and firm, and yield an abundance of silk. They are about of a size, and both varieties are almost always constricted in the middle. Another valuable race is the White Chinese Annual which much resembles the White Japanese but is not as gen erally constricted. We have already seen the importance of getting healthy eggs, free from hereditary disease, and of good and valuable races. There is little danger of prernature hatch ing until December, but from that time on, the eggs should be kept in a cool, dry room in tin boxes to prevent the ravages of rats and mice. They are most safely stored in a dry cellar. where the temperature rarely- sinks below the freezing point, and they should be occasionally looked at to make sure that they are not affected by mold. If at any time, mold be perceived upon them it should be at once rubbed or brushed off, and the atmosphere made drier. If the tin boxes be perforated on two sides and the perfo rations covered with fine wire gauze, the chances of injury will be reduced to a minimum. The eggs may also, whether on cards or loose, be tied up in small bags and hung to the ceiling of the cold room. The string of the bag should be passed through a bottle neck or a piece of tin to prevent injuryfrom rats and mice. The temper ature should never be allowed to rise above 40° Fahr., but may be allowed to sink below freez ing point without injury. Indeed, eggs sent from one country to another are usually packed in ice. They should be kept at a low tempera ture until the mulberry leaves are well started in the spring, and great care must be taken as the weather grows warmer to prevent hatching before their food is ready for them, since both the Mulberry and Osage Orange are rather late in leafing out. One great object should be, in fact, to have them all kept back, as the tendency in our climate is to premature hatching. Another object should be to have them hatch uniformly, ancl this is best attained by keeping together those laid at one and the same time, and by win tering them as already recommended, in cellars that are cool enough to prevent any embryonic development. They should then, as soon as the leaves of the food plant have commenced to put forth, be placed in trays and brought into a well-aired room where the temperature aver ages about 75° Fahr. If they have been wintered adhering to the cloth on which they were laid, all that is necessary is to spread the same cloth over the bottom of a tray. If, on the contrary, they have been wintered in the loose condition, they must be uniformly sifted or :Tread over sheets of cloth or paper. The temperature should be kept uniform, and a small stove in the hatching-room will prove very valuable in pro. viding this uniformity. The heat of the room may he increased about two degrees each day, and if the eggs have been well kept back during the winter, they will begin to hatch under such treatment on the fifth or sixth day. By no means must the eggs be exposed to the sun's rays, which would kill them in a very short time. As the time of hatching approaches, the eggs grow lighter in color, and then the afirnospliere must be kept moist artificially by sprinkling the floor, or otherwise, in order to enable the worms to eat through the egg-shell more easily. They .also appear fresher and more vigorous with due amount of moisture. The room in which the rearing is to be done should be so arranged that it can be thoroughly and easily ventilated, and warmed if desirable. A northeast exposure is the best, and buildings erected for the express purpose should, of course, combine these requi sites. If but few worms are to he reared, all the operations can be performed in trays upon tables, but in large establishments the room is .arranged with deep and numerous shelves from four to eight feet deep and two feet and six inches apart. All wood, however, should be well seasoned, as green wood seems to be injuri ous to the health of the worms. When the eggs are about to hatch, mosquito-net- ting or perforated paper should be laid over them lightly. Upon tbis can be evenly spread freshly plucked leaves or buds. The worms rise through the meshes of the net or the holes in the paper and cluster upon the leaves, when the whole net can easily be moved.