REPORT ON THE DISEASES OF SILKWORMS IN INDIA 69 



healthy atmosphere tend to suffer from flacherie. If the guts of 

 caterpillars kept under these conditions be examined, the peritro- 

 phic membrane will be found to be somewhat thickened and 

 slightly opaque, and the gut content is distinctly less alkaline 

 than in caterpillars reared under healthier surroundings. Tested 

 by Clark and Lub's indicators (Clark, 1920) a normal gut=pH = 

 9*8, while the gut of a worm in a hot moist chamber pH=8"4- 

 8'8. This is a clear indication that the damage is being caused 

 by an unfavourable environment — the growth of bacteria doubt- 

 less follows on this and intensifies the trouble. The bacteria, 

 however, cannot be called the exciting cause of flacherie. This 

 is undoubtedly due to some disturbance in the surroundings — 

 the bacteria always present on the mulberry leaf are given an 

 opportunity to multiply and the second stage of the disease is 

 brought about, but this stage does not necessarily, result until the 

 caterpillar attacked is dead or almost so, for diseased caterpillars 

 showing signs of the external symptoms of flacherie do not always 

 have bacteria in their guts in large numbers. On the other hand, 

 if a batch of worms beginning to show symptoms of flacherie be 

 kept under observation and examined as the time goes on, an 

 increase in the number of bacteria in the gut will usually be noticed 

 as the external symptoms grow more marked. 



The bacteria which are associated with flacherie are limited in 

 number, normally two only being common. These are what I 

 iiave called Bacillus A and Micrococcus a. Both are frequently 

 found in caterpillars which are obviously suffering from flacherie, 

 but only the first seems to be capable of actually intensifying the 

 disease when fed to worms (Experiment 26). Moths suffering 

 from what is often called flacherie in India — that is to say, the 

 presence of bacteria on examination for seed selection — nearly 

 always show almost pure cultures of a bacillus nearly related to 

 A but differing in some details. This I have called Bacillus B. 

 A third— Bacillus C — is sometimes found in caterpillars suffering 

 from flacherie. It was more common in the univoltine worms in 

 Kashmir. Two other micrococci — labelled b and c by me — are 

 also found in diseased worms but in small numbers. Perfectly 

 healthy mulberry worms may show any or all of these bacteria, 

 and they are present in abundance, but especially the micrococci, 

 on mulberry leaves. They may also be recovered from the air — 

 the micrococci again being most prominent here. Thus all the 

 bacteria recovered from caterpillars suffering from flacherie are 

 common forms which can be isolated from ordinary mulberry leaves 

 and healthy caterpillars. I am in complete accord with Sawamura 

 (1905) in his finding that " flacherie is caused not by any special 

 feacteria." 



