REPORT ON THE DISEASES OF SILKWORMS IN INDIA 47 



made better cocoons on the whole. It is possible that the reason 

 for the heavier infection is due to some lessening of the resistance of 

 the caterpillars, owing to some metabolic disturbance caused by 

 the inability of the worm to get rid of water vapour quickly enough, 

 and it is significant that worms reared in warm, damp surroundings 

 have a less alkaline gut-content than those reared under dry and 

 hot, or moist and cool conditions — giving a grey-blue colour with 

 thymol blue (pH=8 , 8.) — see also under flacherie. It is also possible 

 that the leaf being kept moist longer the caterpillars actually eat 

 more and so ingest more spores, while the moisture would tend, at 

 all events in the case of infected cages, to make the spores stick 

 to the leaf while in the dry atmosphere they might tend to fall off 

 the leaf. Whatever the exact cause of the greater percentage of 

 disease, it is clear that a moist atmosphere along with a high tem- 

 perature is very unfavourable, and a rapid renewal of the air in a 

 rearing house is all the more necessary in hot, damp weather. It 

 is interesting to note that the rains and especially August and 

 September are very bad months for pebrine. This is the experience 

 of the village rearers (Appendix II), and it is well borne out in many 

 of the experiments (Experiments 4, lots 4 and 5 ; experiment 6, lots 

 3 to 5 ; experiment 7, lot 1, etc.). Now in these months the moisture 

 content of the air is very high, and as breaks in the rains are fre- 

 quent the temperature at times is very high, so that we have the 

 same conditions as those reproduced in our experiments with the 

 same result. August and September are the worst rearing months 

 for disease and should be avoided if it is at all possible. 



3. In nature the worms would not be underjed, the food supply 

 would be always fresh, and the mulberry eaten would be of the tree 

 type. The food supply of the silkworm is of the greatest importance. 

 It is really just a perambulating stomach and responds wonderfully 

 to good feeding. If worms are underfed "Or improperly fed they 

 succumb much more readily to disease, and even when no disease 

 is present the results may be almost as bad. Experiments 18 to 20 

 give some idea of the effects of proper and improper feeding. The 

 first experiment with normal worms reared in infected cages is not 

 so striking as the second one, although in one lot the underfed worms 

 contracted pebrine while the well-fed ones did not. The next, 

 however, is very impressive. Diseased moths' progeny of the first 

 generation were divided into 3 lots and fed four times a day and six 

 times a day on bush mulberry, and six times a day on tree 

 mulberry. Those well-fed on bush mulberry were infinitely 

 superior to those under-fed, and those fed on tree mulberry were 

 vastly superior to those fed on bush. Plates IV — VI showing the 

 appearance of the worms just before spinning, and the weights 

 of cocoons, although these are of course at best poor, and the 



