THE TROPICAL AGRICULTURIST. 



[September i, 1883. 



i|!orresponil6nc6. 



To the Editor of the Ceylott Observer, 

 TASAR (SILKWOr.M) CULTIVATION. 



19th July 1883. 



Deak Sir.,-rlu Major CoussmaUer's Report on his 

 experiments in ISSl, tlirro .are one or two points 

 which call for the .attention of .all interested in the 

 cultivation of the wild silk-producers. The experi- 

 mental clearing established at Poena (the expenses 

 of which are defrayed by the Indian Government) 

 consists of .a plantation of La<jerslra7uia Indka. The 

 plants .are grown at the distiince of one foot apart 

 in the row.'j, seven feet between each row, and the 

 shrubs are kept topped at the height of four feet. 

 All branches are removed with the pruning-knife as 

 fast as they are bared of leaf by the worms, and 

 in this way a coust.ant supply of succuleut foliMge 

 is produced. 



Major Coussmaker states th.it in the Alimcdmagar 

 CoUectorate the natives habitually cut back their 

 trees very hard, two-thirds of the trees being pol- 

 larded each year, and that this system of cultivation 

 is " most favourable to the Tas.ar worm, for the con- 

 stant lopping of the trees and burning of the branches 

 audi leaves harass the squirrels, birds, lizards and 

 wasps, while the fresh shoots which spring from the 

 mutilated trees alTord the best food possible for the 

 worms." There can be no doubt that the natural 

 foes of the worms are in this way put to a grtat 

 deal of inconvenience, and that the constant attention 

 rendered necessary by the process of regularly prun- 

 ing the shrubs, which Major Coussmaker reeonimends, 

 make» the destruction of lizards and other enemies 

 a rather easy matter, but I cannot concur in the 

 opinion expressed as regards the suitability of the 

 tender foliage as food for the worms. 



In the cultivation of the mulberry-feeding worm, 

 Bornbyx mori, neglect to supply mature leaf has largely 

 tended to increase the debility which either too gre.it 

 kindness, or too little care, has engendered ; and it 

 seems reasonable to suppose that the wild worms, 

 which in their natural state never devour the young 

 leaves unless driven to do so by a scarcity of 

 food, should become speedily debilitated when fed on 

 immature leaf. In attempts made to rear the Alias, 

 3JyliUa and other larvie indoors on branches, the 

 stems of which are plunged in water, it is invariably 

 found that the foliage becomes, sooner or later, dis- 

 tasteful to the worms, and although the strongest of 

 them may escape disease aud spin good cocoons, the 

 majority are more or less affected by the excessive 

 moisture in the leaf. The same deterioration is pro- 

 duced by severe or frtqueut pruning. 



Major Cuusemaker attributes his w'aut of ciunpleto 

 success to the existence of some climatic inlluence 

 that he was unable to contend with, or to the worms 

 having been attacked by small spiders, luoscpiitois, 

 or other minute eueniies. It is quite possible that 

 many of the worms were killed by insects, Imt de- 

 tectiou in oases of this kind should not be difiicult, 

 and I think it almost cert.ain that it was the want 

 of propel ly matured leaf that caused his losses, since 

 he hmiselt admits that some of the worms commenced 

 spiunuig before they w^re full-grown. 



M. \\ aiUy, in one of his reports on silk-producing 

 ■worms reared in London, niLUtions an instance in 

 which a number of Selene and Luna larvie which 

 were fed upon a nut ti ee, that had been tapped 

 and heavily pruned, died one after other, although 

 other worms from the same broods of eggs reared 

 on other tiees growing close by, but unpruned, spun 

 very line cocoons. 



Jt ;s ol the utmost iuiiJottance that the cocijons 



produced, whether of Tasar or other wild species, 

 should be as free as possible of the cement which the 

 worm naturally secretes. Mr. Thomas Wiirdlc, in his 

 recently published handbook of " The Wild Silks of 

 India," states that Major Coussmaker has 'succeeded 

 in obt.aining perfectly white silk by causing the 

 Tasar worm to void all its cement before allowing 

 it to spin its cocoon, but particulars of the method 

 are not given. Inasmuch as the quality and quantity 

 of the cement in the wild cocoons depends largely on 

 the health of the worm, it would seem that in the 

 production of Tasar silk by M.ajor Coussmaker's method 

 a decrease in the amount of .the cement mast bo 

 accompanied by a corresponding loss of vitality in the 

 worm. And this is a very serious cousideration, 

 because it raises a barrier in the way of progress 

 towarels the domestication of the insect, fur it would, 

 of course, be useless to attempt to utilize for breeding 

 purposes, cocoons spun by worms whose constitutions 

 liael been inipaireel in this way. Any natur.alist, I 

 suppofe who has studizd this subject, will admit that 

 the silkworm when it is prevented, by any cause, 

 from cominoneiug to epin its cocoon at the appuiulcd 

 time, is more or less injured by the delay ; and there 

 is also a considerable loss of silk to be taken into 

 account. It is only by rearing one brood after another 

 and by feeding each successive generation on 

 the same kind of plant that any real progress 

 can be m.ade. The moths of this species do not 

 readily pair in confinement, at first, and it 

 would add considerably to the cost of production 

 if the sericulturist were compelled to rely on any of 

 the wild insects he might piocure in the jungles for 

 renewing his stock. 



It is in another direction that we must look 

 to effect an improvement — from the manufacturer's 

 point of view — in Tasar silk. What is re(|uired is 

 that the food-plant should be of such a nature that 

 the worms reared on it would secrete as little as 

 possible of the cement, which at present so greatly 

 depreciates the value of the cocoon ; the plant should 

 also be one on which the worms are easily reared. 

 If these conditions are fulfilled, one of the greatest 

 dithculties in the way of Tasar cultiv.ation will have 

 been removed. There are probably many indigenous 

 trees winch might be utilized with this object, but 

 prolonged experiments will be nccessury to enable us 

 to ascertain the most suituble, auel in this investig- 

 ation the chemical analysis of various kinels of foli.Tge 

 might be of great service. In judging of the effect 

 of the food on the silk, it is important to bear in 

 mind that temperature and other surrounding circ- 

 umstances exert some inlluence on the colour anel 

 texture, and it is not safe to infer from the appear- 

 ance, size .and weight of a few individual cocoons 

 that the food-plant on which they were pro- 

 diicetl is beneficial or otherwise. The Tasar worm 

 is extremely polyphagous, as much, perhaps, in the 

 Ceylon hills as in the h w-eountryj and it is imposs- 

 ible for worms proceeding from such a p.areut slock 

 to produce cocoons of uniform character until they 

 have been reared through several generations on one 

 species of food-plant. In a former letter on this subject 

 I mentioned, I think, tlmt the Tasar worm was found in 

 the hillcountry feeding on the loquat and the Avocado 

 pear trees. I have not Inaei sufheieut time to aseert- 

 ain whether either of these would be of use iu the 

 elireclion indicated, but experiments might easily bo 

 made with them. The sapu is another tree from 

 which good results might be expected, but as I h.ave 

 not yet hearel of a single instance of the Tasar being 

 found in a wild st.ate on this tree iu Ceylon, it is 

 drobable that a good elcal of patience should le required 

 iu inducing the worm to adopt it. Whativer trees 

 are selected, it is essential that they should be per- 

 fectly healthy: no foliage thatj has beeu ' forced by 



