Contagious Diseases of Insects. 279 



Several lots of the larvae were sent me in July and August, 

 representing both the above-described affections, the difference 

 between which was easily discernible. The former disease was 

 apparently that known to the French as Jaunes (sometimes 

 calbd jaundice by the English writers and by some consid- 

 ered the same as grasserie), and the latter was unquestionably 

 fiacherie or mortS'Jiats of the Fi'ench — the schlaffsucht of the 

 Germans. 



The yellow color of the "jaundiced" worms was evidently 

 due to the tint of the blood, and this, again, was as clearly 

 derived from the great numbers of peculiar cellular bodies with 

 which the blood was always loaded, these originating chiefly, 

 if not wholly, in the fatty bodies, as a result of that form 

 of degeneration of those organs in the larva which attends 

 pupation. These bodies, when entire, consisted usually of 

 masses of spheres, each 4 ;U or 5 ^ in diameter, the aggregate 

 attaining a diameter of 30 /a — 40 fx.. The individual spheres 

 often presented a slightly angular outline, as if modified by 

 mutual pressure, and they took no aniline color with which I 

 tried to stain them. These bodies are evidently the mulberry 

 cells and granules of Viallanes, as described in his admirable 

 memoir on the histolysis of insects.* That they originated 

 chiefly in the fatty bodies, I demonstrated by finding masses of 

 them in portions of the fatty bodies themselves and by deter- 

 mining the substantially unaltered condition of all the other 

 tissues of the affected silkworms. 



In the blood of these larvae no bacteria were found, as a 

 general rule, although Professor Burrill occasionally recognized 

 a Bacillus in it ; but in the alimentary canal I never failed to 

 discover great numbers of micrococci and often also numerous 

 examples of Bacterium and Bacillus.f These bacterial forms 



* Ann. Sci. Nat, Zool., xiv. 1,— Art. 1. August, 1882. 



t A transverse section of a jaundiced larva mounted in balsam 

 without staining, shows great numbers of spherical micrococci, some- 

 what unevenly distributed throughout the entire thickness of the wall 

 of the intestine, and fully as abundant in the outer portion of this wall 

 as within. The same micrococci occur in the perivisceral spaces^ 

 being accumulated especially upon the free surface of the organs con- 

 tained therein. A very few are apparent also in the sections of the 

 fatty bodies, and occasionally in the muscles, but none occur in the skin 



