Contagious Diseases of Insects. 



doubles. Stained slides of this exhibit the same characteristics 

 as those made directly from the culture used for the infection, 

 but nothing else is evident. 



On the same day another larva was found dead and black- 

 ened, clinging to the side of the cage, in quite different con- 

 dition, however, from cabbage worms affected by their own 

 peculiar disease. The body contained but little fluid, and that 

 was of a paste-like consistence, full of the above bacilli, which 

 the mounted slides show to be an absolutely pure culture. 



Another larva, which died the following day, August 7, 

 was found to present precisely the same microscopic characters, 

 only large bacilli occurring in the slide. By the 10th ten of 

 the specimens under experiment had either pupated or were 

 evidently making preparations for that change. But two were 

 apparently diseased. One of these last perished on the 12th, 

 its body soft, pale, blackened posteriorly, but not deliquescent. 

 The blood contained a multitude of minute spherical granules, 

 some Bacillus-like structures, more slender than those previously 

 occurring, and also floating cells of the fatty bodies containing 

 mulberry granules, irregular in size, and sometimes showing 

 also a central nucleus. With these were many large micro- 

 cocci, 1 fji in diameter, circular ; or sometimes slightly oval, 

 commonly in singles or doubles, with rarely a chaplet of four. 

 This larva soon became deliquescent, as if affected by the 

 original flacherie of the cabbage-worm ; its condition, in fact, 

 indicating a mingling of two diseases, that conveyed by the 

 infection to the larvae, just described, and the one native to the 

 species. It will be noted that one of the effects of the 

 original infection seemed already to have waned, and that the 

 development of the mulberry cells and granules characteristic 

 of this condition had already occurred, a phenomenon 

 especially significant, since in the native disease of these 

 cabbage caterpillars no similar condition of the fluids was 

 ever seen. Another larva, dead this day, presented appearances 

 so precisely similar to the preceding that no special descrip- 

 tion of it was made. The check lot, in the meantime, had 

 progressed without injury. August 14 this experiment was 

 interrupted, owing to a discovery of the fact that, through some 

 oversight of the attendant, the full number of the larvae placed 



