146 JOURNAL R. A. S. CEYLON. [Yol. VII., PART II. 



cannot expect to obtain from their experiments any pecuniary bene- 

 fit for themselves. In the meantime the thing to be ascertained is 

 the proper food plant of the tussur, for, as I said before, a silkworm's 

 being polyphagous does not prove that it has not a proper tree on 

 which it is more at home than any other. The Arinda silk-worm is 

 polyphagous in a wild state, and yet it has for its proper food plant 

 the castor oil tree. The Atlas is also more polyphagous than the 

 tussur, and yet I know of no tree except the Milnea Rox b urghia n a on 

 which it can be artificially reared for more than one generation ; and 

 while more than a hundred cocoons of the Atlas will be found on a 

 single tree of this species, not more than two or three can be found 

 on any other. I think the proper tree of the tussur must be an 

 Indian species not indigenous to this country, because there does not 

 seem to be any tree here on which the cocoons are to be found in 

 such numbers as to be worth collecting for manufacturing purposes, 

 as is done in India. 



In the meantime the only silk industry likely to be commercially 

 successful is the cultivation of the mulberry. Many persons when 

 they first give their attention to silk production think that wild 

 silk- worms must be more profitable than the mulberry species, but 

 they always become converts to the mulberry in the end. 



Yours truly, 

 Alex, T. Geddes. 



P.S. — -The eggs of the tussur moth hatch in 8 days here. In a 

 temperature of 70° to 75° Fah. they hatch in about fifteen, but they 

 lose their vitality and become putrid if the hatching be delayed for 

 more than twenty days, The breed can therefore be transported 

 long distances only in the pupa state. I omitted to mention that the 

 caterpillar, like that of the Atlas, has the habit of devouring its own 

 cast off skin. 



I enclose a specimen of tussur silk and one of mulberry silk. The 

 mulberry silk is the one tied with red thread.* 



* These can be seen at the " De Soyza Museum," Colombo. 



