3g REPORT ON THE DISEASES OF SILKWORMS IN INDIA 



becomes limp and " loses its elasticity." The animal ceases to move 

 and rapidly dies. After death the body becomes rigid and mum- 

 mified — it does not soften and become rotten— and in a few hours 

 it is usually found to be covered with a white efflorescence, so that 

 it looks like a piece of chalks) If the atmosphere is very dry, however, 

 the white appearance may not be got. (if the disease appears just 

 before the caterpillars are about to spin they may be able to make 

 their cocoons but the moths will not emerge, and on opening the 

 cocoons the pupae will be found covered with the white efflorescence .J 

 The appearance of the dead insects is so characteristic and patent 

 to the naked eye that no microscopic examination is necessary for . 

 the diagnosis of this disease. 



History of the disease. On account of the striking appearance 

 of caterpillars infected with muscardine this disease has been known 

 for a very long time. In the treatise of Olivier de Serres on seri- 

 culture already referred to, this disease is recognized and in the later 

 writings it is described frequently. Despite the statement by 

 Geoghegan (1880) that muscardine was unknown in Bengal, it 

 is most probable that this disease — like pebrine— is not of recent 

 origin. Mukerji (Watt, 1893) reported in 1888 that muscardine 

 had " always been known in Bengal." (As has now been known 

 for nearly a century, muscardine is caused by a parasitic fungus^ 



History and life-history of the causal organism. In 1835 



Bassi demonstrated that the white efflorescence on a caterpillar 

 that had died of muscardine was really due to the(spore bearing 

 " fruits " of a fungus or mould, the vegetative portion of which 

 formed a net work of filaments or mycelium which penetrated 

 the body of the infected caterpillar in all directions^ (Maillot et 

 Lambert, 1906). There are said to be two species of organisms 

 causing this disease — Botrytis bassiana and Botrytis tendla. In 

 the case of the latter the rosy colour of the caterpillar attacked 

 is deeper, more red. 



The disease is 1 transmitted by the spores which are formed on 

 the outside of a diseased caterpillar after its death. The spores are 

 globular in form and somewhat smaller* and of a less refractive index 

 than pebrine spores (Plate VIII, fig. 4) . They are said to remain alive 

 for very- long periods — for over three years under favourable condi- 

 tions. \Jt is not necessary for them to be eaten by a caterpillar in 

 order to cause germination, if conditions of moisture and tempera- 

 ture are correct they will germinate on the outside of the body, each 



* Some authors say that the spores of muscardine are larger than pebrine spores. The 

 spores I have measured were on the average about 3*h-. in diameter while the average for pebrine 

 spores was about 4lJft long by 2 «. wide. All these spores were killed and stained. The mus- 

 cardine spores look larger on account of their globular shape. 



