HL_ DISEASES OF THE MUGA SILKWOR M JANTHERAEA 



ASSAMENSIS).* 



As the Muga worm is only partially domesticated, living all 5 

 its larval life in the open, it might be thought that it would be 

 more free from disease than the completely domesticated, almost 

 helpless, mulberry worm, and to some extent this is true. The 

 parasitic diseases are relatively of little importance. Muscardine 

 seems to be practically unknown, and Nosema spores while present 

 cannot be said to be symptomatic of disease to any appreciable 

 extent (Appendix I E). Black spots are said to be found at 

 times on the bodies of muga worms — these worms are then known 

 as '' photukia." I have not found any of them either in the worms 

 I have examined in Assam nor yet in those that I reared in Kalim- 

 pong. It is, however, possible that these are pebrine spots.f 

 The affected worms are said to be unable to spin cocoons. How- 

 ever this may be, there is no question of pebrine becoming, at pre- 

 sent, a disease destructive to muga. As we saw when considering 

 the question of pebrine in the mulberry worm, the parasite, Nosema 

 bombycis, is not under natural conditions a deadly one. It is only 

 the disturbance caused by domestication and the unhealthy and 

 insanitary conditions involved that have made it so. The com- 

 paratively open life of the muga caterpillar should prevent anything 

 in the shape of an epidemic of pebrine or even occasional loss from 

 that disease being got. For all that, an endeavour should be made 

 to use only examined seed. Seed cannot be too good, and the 

 elimination as far as possible of even a relatively harmless parasite 

 is bound to be beneficial and to help the worms te resist certain 

 other diseases which are undoubtedly serious. 



The silkworm fly is a thing that has to be reckoned with, as- 

 is an ichneumon fly, but it is of course impossible to protect the 

 worm against these. Given the freedom of well-sized trees, as these 

 worms are, the toll that other insects levy is very heavy— as is 

 the loss caused by insectivorous birds, bats and lizards. 



* According to the note by J. Henry Watson given by Lefroy (1916) en p. 153 of the Ap- 

 pendix Vol., at least 3 distinct species are being bred in Assam as muga — the eri and the 

 tasar are also said to be mixed. It is possible that more hardy races of muga could be got if 

 these species were separated and bred true instead of being crossed indiscriminately as they 

 seem to be at present. 



■f- Since writing the above I have succeeded in obtaining specimens of muga worms suffering 



from " photukia" through the kindness of Mr. Dutta of the Assam Sericultural Department,. 



who diagnosed the disease and sent me specimens. It is typical pebrine — the spots being the 



same as/in mulberry worms but I think rather smaller and more regular. Mr. Dutta estimates 



the loss from this disease at about 3 per cent. 



( 80 ) 



