FtBKUARY, 1902.] 



KNOWLEDGE 



31 



the oak. Cocoons were first sent to Lyons, from wliich 

 moths were in due coui-se hatched out, and shown at 

 the Paris Exhibition of 1855. The silk has some of 

 tlio properties of wool and cotton, as well as of ordinai-y 

 silk, and thus approximates to the Tusscr (or Tusseh) 

 silk of India, a nanic which is commercially applied to 

 tho produce of many of the window-moths. Of the 

 true Indian Tusser moth (A. inijlitta). which is found 

 both in lower Bengal and the Punjab, the silk is perhaps 

 even more valuable than that of the species last named. 

 Tho silk is so coai-se and knotty that it has to be 

 carded instead of wound, and from it are made 

 the well-known khaki-coloured tusser fabrics that 

 are almost indestructible with fair usage. An excellent 

 account of this moth and its silk is given by Mr. Cotes 

 in an ai-ticle on the " Wild Silk Insects of India,'' pub- 

 lished in Iiidinu iluxeum Xote$ for 1891, where mention 

 is also made of other kinds of silk-producing species. 

 Among these latter is the Atlas moth (.1. atltix), which 

 is one of the largest in the group. Its catei-})illar is 

 pale olive-green and lavender in colour, with a con- 

 spicuous D-shaped scarlet mark on either side of the 

 hinder end. Like those of other members of the group 

 it is armed with a number of spine-like warts. 



The species that has perhaps attracted the largest 

 amount of attention is, however, the ailauthus moth 

 (.4. rynfhia). which is a native of Japan, where the 

 catcq^illar feeds on the ailanthus, or false Japanese 

 vai^nish-tree. The wings of this handsome moth are 

 ornamented by a conspicuous white line, externally to 

 which is another band of rose ; each wing also having 

 a irescentic spot. This fine species was introduced 

 into France in 1857 or 1858, where it has since been 

 acclimatized, its food-plant flourishing well in that 

 country. At first the cocoons could be made to yield 

 by carding nothing more valuable than short-fibred floss- 

 silk, but subsequently means were devised of obtaining 

 long threads of an excellent description of silk. The 

 ailanthus moth is found in China as well as in Japan. 

 In India it is replaced by the closely allied castor-oil 

 moth {A. ricini), which yields a silk of very similar 

 ch.aracter. By some writers this species is regarded 

 only as a variety of the last. Dai-win, in his " Animals 

 and Plants under Domestication,' states, for instance, 

 that " tho Arrindy silk moth (as it is often called) intro- 

 duced from Bengal, and the Ailanthus moth from 

 tho temperate province of Shan Tung, in China, belong 

 to the same species, as we may infer from the identity 

 in the caterpillar, cocoon, and mature states; yet they 

 differ much in constitution ; the Indian form ' will 

 flourish only in warm latitudes,' the other is quite hardy 

 and withstands cold and rain.'' Apart from its tender 

 constitution, the difliculty of cultivating the castor-oil 

 plant, even in the south of France, offers an obstacle 

 to the permanent acclimatization in Europe of the firsts 

 named form. 



Omitting mention of certain other silk-yielding cater- 

 pillars, a few lines may be devoted to the subject of 

 spider-silk. The gossamer-like nature of this delicate 

 substance is familiar to all; and in fineness and tenuity 

 the threads far suqjass ordinary silk. From time to 

 time more or less successful attempts have been made 

 to utilize this substance; and recently a manufactory 

 has been established in France where the ropes for 

 military balloons arc made from spider-silk. The factoi-y 

 is situated at Chalais-Meudon, near Paris. The spidei-s 

 which supply the silk are arranged in dozens above 

 a revolving reel, upon which the threads arc wound ; 

 each spider furnishing from thirty to forty yards of 



thread. After the removal by careful washing of tho 

 reddish sticky out«r layer, the threads are twisted into 

 a yai-n, which, although considerably more expensive, 

 is both lighter and stronger than a cord of cateiiiillar 

 silk of the same calibre. One of the chief difficulties 

 connected with the manufacture is the feeding of tho 

 spiders. 



The third and last description of silk used for manu- 

 facture is afforded by the byssii^, or mooring-rope of the 

 great mussel-like bivalve commonly known by its Italian 

 name j/iiiiiti, a word which properly denotes the fin of 

 a fish, but is applied to the shell on account of its fin- 

 like shape. The pinna, which grows to a length of two 

 feet or more, is a semi-translucent shell shaped like an 

 isosceles triangle ; the byssus issuing on one side from 

 between the two valves a short distance from the apex. 

 This byssus consists of a silk so fine in quality as to 

 produce a most delicate fabric when worked up. Al- 

 though the supply of this pinna silk is too limited to 

 be of any commercial importance, it has from time 

 immemoi-ial been manufactured into small articles of 

 dress, such as gloves, stockings, and caps, at Taranto. 

 Originally these were reserved for imperial or royal 

 use, and at the present day are made rather as objects 

 of cui'iosity than of use ; the manufactured silk is of 

 a delicate hair-brown coloin-. For some reason or other 

 the pinnarsilk is mixed with about oue-tliird its bulk of 

 ordinary silk previous to being woven. Some years ago tho 

 price asked for a pair of pinna-silk gloves at Taranto 

 was six lire, while eleven lire were demanded for a pair 

 of stockings. Specimens both of the byssus and of the 

 manufactured silk are exhibited in the Natural History 

 Museum at South Kensington. 



In addition to its importance as the chief silk-pro- 

 ducer of the world, the silk-worm also yields the finer 

 descriptions of the substance known by the not vei-y 

 elegant title of " catgut." To obtain the catgut, or 

 '' gut," the silkworms must, however, be killed just 

 before they commence cocoon-spinning, so that silk and 

 gut cannot be obtained from the same individuals. Con- 

 sequently the finer descriptions of gut, such as that 

 used by th& fly-fisher, arc expensive. 



The great manufactory of fine gut at the present day 

 is situated on the island of Plocida, in the Bay of 

 Naples, where, however, only a small proportion of the 

 silkworms uecessai^y for the manufacture are raised, the 

 great bulk of these caterpillai's being obtained from 

 Torre dell Annunziata and other towns in the neighbour- 

 hood, where there are large silkworm-breeding establish- 

 ments. 



According to an account published a few years ago, 

 the process of manufacture of " fili di seta " (" silk- 

 threads ") as the gut is locally termed, is as follows: — 

 The silkworm is selected when fully matured, that is 

 to say, at the moment when its nourishment ceases, 

 and just before its metamorphosis. It is then cut open, 

 great care being taken not to injure the membrane 

 of the silk-glands there, which usually reach the length 

 of thirteen to twenty mms., with a diameter of one and a 

 half to two mms. ; these are then removed, and put into 

 a pickle, which is the keynote of the whole pro- 

 cess, and the secret of which is carefully kept. 

 When the pickling process is over, the work- 

 people, who are mostly women, take one end 

 of the gland in their teeth and draw the other end 

 with their hands. This part of the work reqviires great 

 dexterity, for the threads are drawn out to the length 

 of from thirty to fifty ems., and the whole value of the 

 product depends upon its length in i-elation to its thick' 



