294 fllinois State Lahomtonj of Natural Histori/. 



rapid pupation of these specimens will be noticed, as compared 

 with those treated with the infection material, — a fact 

 consistent with what I have uniformly observed with regard to 

 the effect of these diseases. 



On the 17th four worms were drowned in a dish of water 

 containing the food plant in the breeding cage. The fluids of 

 these worms were carefully examined with a microscope, and 

 careful studies were made of stained covers of their blood and 

 alimentary contents, but no possible bacteria of any sort were 

 detected in them. On the 21st three more larva pupated, and 

 on the 23d three died. Unfortunately, the latter fact was not 

 reported by the assistant in charge in time to permit an exam- 

 ination of these dead worms. All the remaining larvae pupated, 

 the imagos commencing to emerge on the 26th. 



Although the results of the foregoing experiments were 

 somewhat less definite than might be desired, yet they clearly 

 indicate the transference of the disease affecting the silkworm 

 to healthy larvas of Pieris rapce. It would perhaps have 

 been difficult to establish by a study of the bacteria alone any 

 marked difference between the disease resulting from this 

 experiment and that native to the cabbage worm, but the 

 symptoms of the two diseases were so unlike as to make 

 it impossible to confound them. The general absence of the 

 peculiar discoloration of the common flaclierie of the cabbage 

 worm, and of that rapid post mortem deliquescence even more 

 characteristic of it, leave no doubt as to the actual difference 

 between this induced disease and the spontaneous affection. 

 That the artificial disease was identical with that of the silk- 

 worm, differing only in such a degree as was to be expected 

 when attacking such widely different larvse, is rendered 

 probable, not only by all the attending circumstances, but also 

 by the occurrence in the cabbage worm of the myriads of 

 mulberry granules characteristic of the affection in the silk- 

 worm. This fact is especially significant, since in all our 

 numerous examinations of the native flacherie of the cabbage 

 worm this condition of the fluids was not once observed. 



I followed this experiment with a similar one in the field, 

 applying the same fluid to a number of cabbages infected by 



