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Show 300 SILK-MOTllS. CHAP. VIII. SILK-MOTHS. THESE insects arc in several respects interesting to us, more especially because they have varied largely at early peri?ds of life and tho variations have been inherited at correspondmg periods. As the value of the silk-moth depends ~~tirely on the cocoon, every change in its structure and qual:tieshhas been carefully attended to, and races differing much m t e coco?n, but hardly at all in the adult state, have been produced. With the races of most other domestic animals, the young resemble each other closely, whilst the adults differ m.uch. . It would be useless, even if it were posstblo, to descnbe all the many kinds of silk-worms. Several dist~ct species exist in India and China which produce useful silk, and some of these are capable of freely crossing with the common silk-moth, as has been recently ascertained in France. Captain Hutton63 states that throughout the world at least six species have been domesticated; and he believes that tho silk-moths reared in Europe belong to two or three species. 'l'his, however, is not the opinion of several capable judges who have particularly attended to the cultivation of this insect in France; and hardly accords with some facts presen~ly to be given. The common silk-moth t(Bombyx 1nori) was brought to Constantinople in tho sixth century, whence it was carried into Italy, a.nd in 1-194 into Franco.64 Everything has been favourable for the variation of this insect. It is believed to have been domesticated in China as long ago as 2700 n.c. It has been kept under unnatural and diversified conditions of life, and bas been transported into many countries. 'rhere is reason to believe that tho nature of tho food given to the caterpillar influences to a certain extent the character of tho breed.65 Disuse has apparently aided in checking the development of tho wings. But the most important clement in the production of the ronny now existing, much modified races, no doubt has 63 'Transact. Entomolog. Soc.,' 3rd series, vol. iii. pp. 14.3-173, and pp. 295-331. 64 God ron, 'De l'Especc,' 1859, tom. i. p. 460. The antiquity of tho silk~worm in China is given on the authority of Stanislus Julien. 65 See tllc remarks of Prof. Westwood, General IIcarscy, and others, at the meeting of the Entomolog. Soc. of London, July, 18Gl. CHAP. VIII. THEIR DIFFERENCES. 301 been the close attention which has long been applied in many countries to every promising variation. The care taken in Europe in the selection of the best cocoons and moths for breeding is notorious,66 and the production of eggs is followed as a distinct traue in parts of Franco. I have made inquiries through Dr. Falconer, and am assured that in India the natives are equally careful in the process of selection. In China the production of eggs is confined to certain favourable districts, and the raisers arc precluded by law from producing silk, so that their whole attention may be necessarily given up to this one object.6 The following details on the differences between the several breeds aro taken, when not stated to the contrary, from M. Robinet's excellent work Gs which bears every sign of care and large experience. The eggs in the different mces -vary in colom, in shape (being round, elliptic, or oval), ~nd in size. The eggs laid in Juno in the south of France, and in July m the central provinces, do not hatch until the following spring; and it is .in -vain, says M. Robinet, to expose them to a temperature gradually rrused, in order that tho caterpillar may bo quickly developed. Yet occasionally, without any known cause, batches of eggs are produced, which immediately begin to undergo the proper changes, and are hatched in from twenty to thirty days. From these and some other analogous facts it may be concluded that the Trevoltini silkworms of Italy, of which the caterpillars are hatched in from fifteen to twenty days, do not necessarily form, as has been maintained, a distinct species. Although the breeds which live in temperate countries procluco eggs which cannot be immediately hatched by ai·tificial beat, yet when they are removed to and reared in a bot country they gradually acquire the character of quick development, as in the Trevoltini races. 69 Oaterpillars.-These vary greatly in size and colour. The skin is generally white, sometimes mottled with black or grey, and occasionally quite black. The colour, however, as M. Robinet asserts, is not constant, even in perfectly pme breeds; except in the race t·ign!e, so called from being marked with transverse black stripes. As the general colour of the caterpillar is not correlated with that of the silk,7° this character is disregarded 66 See, for instance, M. A. de Quatrcfage's 'Etudes sur les Maladies actuelles du Vera Soie,' 1859, p. 101. 67 My authorities for these statements will be given in the chapter on Selection. 68 'Manuel de l'Educatcur de Vers a Soic,' 1848. 69 Robinct, idem, pp. 12, 318. I may add that the eggs of N. American silkworms taken to the Sandwich Islands were very irregularly developed ; and the moths thus raised produced eggs which wore even worse in this respect. Some were hatched in ten days, and others not until after the lapse of many months. No doubt a regular early character would ultimately have been acquired. See review in 'A themeum,' 1844, p. 329, of J. Jarvcs' 'Scenes in the Sandwich Islands.' 70 'The Art of rearing Silk-worms,' translated from Count Dandolo, 1825, p. 23, |